FIRE DAMAGES OF CLOTHES AND SKIN

Forensic examination of injuries and in cases of violent death.

 

Fire injuries

 

FIRE INJURIES

 

Firearm appeared in the middle of XIV century and since that times it is widely used in fighting actions.

As the incidents with using firearms last during very short time, in most cases it is almost impossible to reproduce real events without specialist help, even in the cases with witness presence. That is why the destination of forensic examination of bullet wounds presents is obligatory part of investigation and the results of expert researches frequently are very important and decisive proof sources during such investigations. Firearm is an instrument with which it is possible to propel a projectile (missile) by the expansive force of gases generated as result of combustion of the propellant (gun powder) in a closed space.

Firearm injuries are wounds caused to the body tissues due to impact, entry and passage of a missile discharged from a firearm.

 

Firearms

Firearm is the weapon that uses kinetic gunpowder combustion energy to throw out the projectile from the trunk. It is subdivided on artillery and rifle. A rifle firearm can be grouped as individual (or hand) and collective one. The injuries which are caused by explosion of different explosive substances or devices, belongs to explosive trauma.

Shortly, a firearm is an instrument with which is possible to prople a projectile (missile) by the expansive force of gases generated as result of combustion of the propellant (powder) in a closed space.

 

 

 

 

9 mm. Browning

 

 

revolver

In ordered to do examination of firearm trauma correctly, a specialist in branch of forensic medicine must be well acquainted with wound ballistics, with arm and ammunitions, that are most often to be found in expert practice.

A rifled firearm is small-bore (5-6 mm), middle-bore (7-9 mm), large-bore (more then 10 mm). A bore is the distance between contrary fields (on diameter) of trunk in millimeters in threaded firearm or diameter of trunk in smooth-bore arm.

Classification of firearms. The individual shooting firearms are mainly occurred in forensic practice. Such weapons are classified into the following groups:

1. According to purpose:

·     Battle (carbines, sub-machine guns pistols)

·     Hunting (shot guns, rifles)

·     Sports (pistols, rifles)

·     Special (alarm) Atypical (defect and self-made)

2. According to length of a barrel:

·     Long-barreled (carbines, rifles, machine guns)

·     Middle-barreled (sub-machine guns)

·     Short-barreled (pistols, revolvers)

3. According to property of a barrel:

·     Rifled (sub-machine guns, revolvers, rifles)

·     Smooth-bored (shot guns)

·     Combined (hunting rifles, sports weapon)

4. According to calibre:

·     Small-calibre (4-6 mm.)

·     Medium-calibre (7-9 mm.)

·     Large-calibre (more than 9 mm.)

5. According to the mechanism of a shot:

·     Automatic (machine-guns)

·     Semi-automatic (carbines, pistols)

·     Non-automatic (hunting rifles)

Principally all types of fire weapons are subdivided into smooth-bored and rifled firearms.

Components of firearms. A firearm consists of 3 main parts: a barrel, action (breech block incorporating the firing pin, hammer and trigger), and a grip or a but. A barrel consists of a steel tube in the form of a hollow cylinder of various length. Its proximal end is called the breech end and the distal end which is always open is called the muzzle. The breech end has a chamber to accommodate the cartridge. A breech block is generally pierced in the centre of the action to accommodate the firing pin. A trigger is a lever, situated below the lock. A grip or butt is the part of the weapoormally gripped in the hand.

 

 

Ammunitions

 

Ammunition. One unit of ammunition is a cartridge. It consists of a cartridge case; a propellant charge; a projectile; wads (in shotgun cartridge).

 

Different catridges

 

A cartridge case is the outer shell of the cartridge generally made of brass. It has a flat base with the primer cup (percussion cap) in the centre. Primer means a small metal cap holding sensitive composition that is detonated by a blow from a firing pin. The priming composition may contain Mercury fulminate, Potassium chlorate, Antimony sulphide, Barium nitrate etc.

Propellant charge means the powder, ignition of which by the flame from the primer, provides the energy for flight of the missile out of the gun barrel. It lies between the primer and the projectile. The propellant charge is composed of black, smokeless or semi-smokeless gunpowder.

Projectile means an object propelled by the forces of rapidly generating hot gases. This is a bullet in rifled weapon or lead shots (pellets) in smooth-bored firearms. A bullet is made of lead. It may be jacketed either fully or partly with cupronickel. The shape of the bullet is usually conical. Its tip (known as nose) may be pointed, rounded or flattened.

 

Structure of the cartridge for  smooth-bored weapon

 

Wads are normally present in shot gun cartridges. They may be made of felt, cardboard, stout paper or plastic. The wads provide important functions. Thus, they: separate projectile from the propellant, seal the bore effectively, prevent expanding gases from escaping and promote optimum pressure to develop.

 

 

A Bullet is a small projectile in view of steel or leaden ingot of oblong form with sharp or blunt end for firing from rifles, sub-machine-guns, pistols, guns, machine-guns. They are different: long, intermediate and short; sharp and blunt ended. They are subdivided on usual and special. In shot-guns the leaden and combined bullets are used, such as Jakan, Brenneke, Mayer and others. Bullets from different riflearm differ in mass, for example, the weight of bullet for Makarov’s pistol is 6,lg, and to submachine gun Kalashnikov and SCS carbine is 7,9 g.

 

The defeating projectile in hunting cartridges most often is a pellets , that actually are leaden small balls. They can be made by factorial and home-made method. In hunter cartridge the cardboard wad is placed right on gunpowder , then felt wad, to create the best hermetic attach to combustion of gunpowder. Now wad-containers for pellets from polyethylene are used. Any wad, found in the place of event or in wound, is valuable material evidence, that’s why it must be withdraw and given to investigator.

 

Shot and its mechanism

 

Firing (Operating) mechanism. Mechanism of discharge of projectile in firearm is the following: a trigger is pulled → a firing pin strikes the percussion cap of the projectile → detonation of the primer → ignition of main propellant charge → rapid formation of expanding hot gases at very high pressure → missile is propelled out of the barrel giving it the necessary muzzle velocity  video .

A Shot is a gunpowder flash in cartridge, that is found in cartridge-chamber of firearms, and throw out of bullet (pellets) from trunk under pressure of powder gases, formed by this flash.

While living a barrel, a bullet revolves around its axis with speed of 2-3 thousand of turnovers per second, that is necessary for its stability in flight and increase of the flight distance. This motion is conditioned by presence on internal surface of trunk of riflearm spiral slices, which actually are narrow ditches.

The mechanism of formation of bullet wound is very complicated. A projectile (bullet, fraction) has enormous kinetic energy, which transfers to organism tissue while entering. Effect of firearm projectile on tissues depends on the number of factors: from bullet or pellets mass, their speed and physical state of tissues. Piercing bullet ability is conditioned by its ” living force” at the moment of wounding. While increasing the weight of bullet twice the kinetic energy increases twice too. At the same time the increasing of its speeds twice calls 4 time augmentation of energy. If the mass is constant, a bullet that has greater speed will have greater energy video  .

 

Entrance and exit holes

 

Entry (entrance) wound. A typical fire injury is composed of an entry wound (hole), wound canal and an exit wound (hole). Medico­legally, it must be perfectly determined where the projectile enters the body and where it comes out. It may establish on the base of morphological features of entry and exit wounds.

Thus, the following characteristics are typical for entrance fire wounds: Their shape is usually round or oval which depends on the angle of discharge (right or acute). Size is commonly slightly smaller than the diameter of the missile due to elasticity of the skin. One of the most important features of an entry wound is «tissue defect» («minus-tissue») that was firstly described by famous Russian surgeon Nykolai Pirogov in 1849.

 

 

This is due to own penetrating action, a bullet punches a hole in the skin and drives away inside the wound canal some pieces of punched tissues. That’s why it is impossible to pull together margins of the wound without formation of the skin pleats. Very commonly, there are 4 so-called «rims» (rings, collars) in entrance wounds. They are «abrasion rim», «desiccation rim», «dirt rim» and «metallization rim». An «abrasion rim» is seen around the hole and it is caused by the friction of the missile when it indents the skin during penetration. It is so narrow, not more than 1-2 mm. in width. A «desiccation rim» can be found upon the margins of the wound since 12-24 hours after death as a dark yellowish collar. When a bullet penetrates the skin a dirt effect of the projectile takes place and a «dirt rim» is formed upon the edges too. It can be revealed as a black or dark thin ring in an entry hole. The friction and heating effect of the missile are accompanied by the formation of a «metallization rim» too. The other diagnostic signs of entry wounds are: regular, circular and inverted margins, additional factors of a shot (tattooing, burning, blackening) may be seen, they are smaller than exit wounds video  .

Exit wounds. They vary in shape and size. Exit wounds may be stellate, cruciate, linear. They are bigger than entry wounds. The edges are irregular, serrated and everted because the missile forces its way out. Abrasion, desiccation, dirt and metallization rims are usually absent. All accompanying components of a shot are absent too.

 

 

Clothing is turned out.

A bullet or pellets provokes mostly mechanical traumatic action. A Typical bullet wound consists of entrance wound, wound channel and exit wound in the condition of through wound. There are also blind, tangent and direct bullet wounds. While examination of bullet injuries always arises question about direction of shot, about cosituation of injured and shooting, about direction of wound channel in man body etc.

The entrance bullet wound (or entrance hole) is small, 6-8 mm in diameter, rarely bigger, frequently corresponds to the bullet diameter or is less for 1-2 mm then this diameter. However in some cases entrance hole can be bigger then exit. This is reasoned by gases action under the condition of very shot shooting distances. In majority of cases the entrance hole a little lesser then bullet diameter. The skin properties explain this, the skin stretches when bullet passes through it and then it decreases. So it is impossible to make correct conclusion about arm caliber having the information only about the size of entrance hole.

It can be of round, or oval form, if bullet enters the body by its main part perpendicularly to skin surface or under insignificant corner to it. A Round form of entrance hole is explained by the fact that a bullet while entering the body with its front end, makes the hole, that has a form almost similar to cross-section of round bullet. An oval form of entrance of bullet wound can be conditioned by immersion of bullet into skin by lateral surface, uneven skin contraction, that displays stronger on the direction of elastic fibers, skin fold wound, change of body position, associated with displacement of tissues in wound surrounding areas, etc. Other forms of entrance hole meet rarely.

Having considerable kinetic energy, a bullet beats out skin surrounding areas, that are situated in front of it. As the result a cloth defect appears. A cloth defect is one of reliable signs of firearms entrance hole. This sign explained that according to entrance hole the part of skin is absent, and because of it the ends of wound can not be quite together, a wound gapes. The most frequent cloth defect has a round or oval form. It sizes are lesser then bullet diameter, which is explained by skin tensility during passing bulled through it. A cloth defect determines by comparison of wound ends: if they do not become together or become together for skin tension with formation of folds, it means the defect is present.

 

The other sign, which is very important in recognizing of entrance hole, is a presence of edging abrasion around it. A contusion edge or edging abrasion surrounds entrance hole by narrow edge of 1-2 mm. It is conditioned by the fact that in the moment of bullet passing through the skin, the skin presses a little and stretches by reason of its elasticity. On the strength of this the edge of wound, that collides with bullet, under this hides and scratches by bullet’s lateral surface. If bullet enters the body perpendicularly to skin surface, the edging abrasion is usually roundshaped and has identical width all perimeter. If bullet makes a angle with the skin, the edging abrasion will be wider from that side, where a bullet and skin composed a lesser (sometimes sharp) angle, because from the sides of sharp angle skin traumatizes and scratches in greater measure, than on the part of obtuse angle.

 

Defect of the tissue and abraded ring in entry fire wound

The greater kinetic energy of the bullet is, the greater tissue defect and the more narrow edging abrasion are. A width of edging abrasion depends also on size and form of bullet. An edging abrasion is not always well expressed, specially on torn big entrance holes.

 

M. 1. Raisky offered to distinguish also drying edging, which appears on corpse in 12-24 hours after death by reason of posthumous skin drying out in the area of its abrasion on wound edge according damaged epidermis. A drying edging looks like a little wider (0,5-1 mm), than edging abrasion, edge, darkly-brown or red-brown colors, dense to the touch. As a rule it fully or partially ablates by surgeons while primary wounds treatment.

While penetration of the bullet into body as it rubs the edges of entrance hole, and different parts that are always present on the surface of the bullet stay there. As the result of this there is a presence of darkly-gray or black narrow edge on the edge of entrance hole, which is called ring of mud (see picture upper).

This is another sign of entrance bullet wound. If the shot is through the clothing the rubbing edge on wounds of skin is frequently absent, because major part of substances, that were on bullet, remains on edges of clothing.

As a rule, a rubbing edge coincides with edging abrasion, covering it.

A rubbing edge enables not only to distinguish an entrance hole from exit, but sometimes can be the base for answering the question about succession of shot.

In projection of edge of mud in the entrance bullet wound, there disposes one more ring – metallization edge which is formed by procrastination of shallow metals lobules on wound or damage of tissues edge. The edge of entrance bullet wound in typical cases is toothed or smooth, that depends on size of kinetic energy of bullet: the greater bullet energy is, the more equal edges are. Is also depends on a bullet end form. It is a fact, that the sharp bullets form more equal edge, and rounded or blunted is toothed.

In majority of cases entrance hole lesser then exit. But this conformity to natural laws has and exclusion, about which it was already remembered. An entrance hole can be identical with exit (for example, when they are disposed close to one another) or even bigger (while point-blank shooting, sometimes – from shooting from small distance because of gases action etc.).

The entrance hole is also testified by a presence of black-gray soot, not burnt particles of dust and other components of shot around damaged clothes or skin.

An Exit wound (exit hole) is a wound, through which a firearm products (bullet, it parts, pellets) leave a body. It is formed in other way than entrance one. A Bullet, passing over tissues, approaches skin from within and stretches it out in front of oneself in cone appearance. Overcoming tissues resistance, a bullet loses part of kinetic energy. An epidermis on protrusion top cracks in radial directions and a skin burst. That is why the form of exit hole is most often radiant, crack-viewed or indeterminate, that depends on wound localization and skin elasticity in wound allotment.

The Contrary wound edges well compare without pulling the skin, exactly adjoin one to another and close down hole. So, an exit bullet wound does not have a tissue defect, and if it presents, it is considerably smaller from defect in entrance wound.

Edges of exit hole are toothed, torn with slight tears that go away to the sides. The attendant shot factors such as soot, not burnt particles of dust and etc.

An Exit hole does not have the rubbing, metallization or abrasion edges. Scratching of epidermis sometimes is observed by exit hole, when skin allotment was pressed to rock-bottom – to chair back, to wooden wall, sex, sword-belt strap etc.

In majority of cases exit hole is greater then entrance. A difference in size is because in the moment of entrance into the body the bullet flies correctly, and in the moment of going out of the body it can turn a little, to become deformed, to take some parts of bones. There can be other causes, which have been already mentioned.

You must remember that if there is one entrance wound, there can be several exit holes. A bullet sometimes is deformed in the body and subdivided on separate parts, and each of them goes independently, forming the separate holes. In such cases it is possible to find pieces of bullet in tissues, especially during Rh- research.

It happens, that typical signs of entrance or exit holes are absent or unclearly expressed. Different factors are important for correct hole recognizing. Difficulties arise not only from shooting from big distance, but also from close distance. This happens in cases, when a shot is done through the clothes, and the clothing is absent or became unsuitable for research (inundated by blood).

 

Additional shot factors and their action

 

Additional factors (accompanying components) of a shot. When a weapon is fired, smoke, flame, burnt, particles of metals and the gases of combustion leave the barrel together with the portions of burnt, unburnt or partially unburnt grains of powder. These contaminants usually follow the projectile immediately during discharge. They are called in forensic ballistics as accompanying components (additional factors) of a shot.

Flame of a shot is formed due to combustion of propellant and results in burning of outer clothes or around the entry wound. Intensity of burning depends on the type of powder: it is more if black powder is used and less if the cartridge is equipped with smokeless powder. The distance (from the muzzle to the target), when appearances of flame may be found, varies between 3-5 cm. to 15-20 cm. in military weapons and up to 0,8-1 m. in hunting guns.

Powder gases can have mechanical (contusing), chemical and thermal actions in the area of entry wound. Contusing action of gases is manifested in splitting of the skin in an entry wound. Formation of parchment spots can be revealed too. Chemical action of powder gases causes bright red color of surrounding tissues in an entry wound due to formation of carboxihae­moglobin and carboximyoglobin. Thermal action of gases is not considerable and is reflected by scorching. An average range of gases action is near 15-20 cm. from the muzzle and depends upon both the gun and ammunition used.

The soot is mainly composed by a discharged primer. It can be seen as deposition of smoke around the entrance wound and is termed in forensic ballistics as blackening. This may be round or oval shaped (depends on theangle of shooting) and suggests (if present) the range of a shot up to 20-30 cm. from the muzzle.

When the gun is fired, propellant is not discharged completely. Therefore burnt, unburnt or partially unburnt grains of powder are formed. They are usually driven into the skin, can be easy revealed around entrance wound and are called as tattooing. Tattooing caot be wiped off. The grains of gunpowder fly furthest.

Particles of metals follow the bullet or pellets together with propellant gases and can be deposited on a target. Specific investi­gating methods are usually used for identification of irritans: X-ray examination, thin-layer chromatography, spectroscopy, application of color prints etc.

During the shot not only the bullet or pellets fly out of barrel but also products of explosive gunpowder decomposition and other components, which leave the traces on cloth or man body and even can damage them. These are so called as additional or concomitant factors of shot. They are: post of constricted air that appears in front of bullet, powder gases, flame, soot, not burnt gunpowder corns, pieces of metal, drops of gun oil, if arm was smeared.

They come out of a rifled gun only on insignificant distance. Exposure of additional shot factors on man’s cloth or body or traces of their action tells that this is bullet wound, about presence of entrance hole and enables to set shot distance.

At the moment of shot gases, flame and bullet go into the hole formed by post of constricted air. That’s why a tissue defect, that usually is caused by bullet, can be absent and not expressed.

There is mechanical and chemical action of powder gases (or hot gases). Mechanical action appears in damages of clothes, skin, fat base, muscles, internal organs, destruction of bone, specially flat ones, exfoliating of skin, that depends on gase pressure and distance of a shot  (5-10 cm). A Bullet, which enters into hole, formed by gases, does not leave an entrance hole. That’s why it is impossible to find them while putting together torn pieces of clothes or skin. Traumatic mechanical action is promoted by volume of gases, which come out a gun. On distance within the pale of shot gases action they can commit a skin slaughter (hurt).  As consequence of this action and next skin drying out there is appearance of brown blots of parchment closeness around entrance bullet wound.

 

Mechanical and chemical action of the shot gases

The chemical action of powder gases is, that at an shot closely, particulate and from a very close range oxide of Carbon, which one places in gases (10-40 %), very fast incorporates with a hemoglobin of a blood of an injured site (segment). Owing to it around of an input fire foramen there is a bright red color of a blood and muscles. Thermal operating of gases of smokeless powder is possible, but optional.

 

Kinds of bullet action on human tissues. The internal effects of a bullet depend upon its kinetic energy which is firstly characterized by muzzle velocity — the speed with which the projectile comes out the barrel. According to this, there are 4 kinds of bullet action on the tissues: explosive — the highest muzzle velocity, near 500-1000 m/s, hydrodynamic action, extensive destructions of internal organs); penetrative — bullet velocity is nearly 250-400 m/s, defect of tissues «minus-tissue» is formed, crushing effect inside the human tissues; cuneiform — bullet velocity is not more than 100-150 m/s, it caot penetrate the tissue, it is typical for an exit wound; contusive — a bullet loses its energy, velocity decreases, it only blows the tissues resulting in superficial wounds or grazes.

 

Determination of shot distances

 

The flame of a shot is one of the additional factors, which one accompanies with an shot. At an outrigger boom the black powder from a bore will reject oddments of combustion of a powder charge and capsule structure – fire flame, which one consists of the incandescent firm and kindled infrequent parts. The black powder derivates a flame and weight of incandescent firm parts, which one invoke (produce) ignition of clothes (clothing), scorching of tissues, skin burns, scorching of a hair. At an outrigger boom by smokeless powder the flame can sometimes call minor scorching of tissues of woolen clothes (clothing), scorch of a down hair (as acts faster in matching with a flame of black powder). The flame of an outrigger boom reaches up to 15-20 cm from the muzzle end of weapons, and at shot by black powder from the hunting gun – up to 0,8-1 m.

Smoke black as one of the additional factors of a shot, represents small grains of a miscellaneous structure, which one are born from a bore out by powder gases. Caking around of an input fire foramen on an interrupting in view of black –grey raid of miscellaneous intensity, they derivate a reference picture intrinsic to injuries by shot from fire-arms.

During a shot not all powder is decomposed. Some grains come out a bore after bullet and are partly burnt. Each grain can be esteemed as  separate small balls, which one has large initial velocity and some alive force. It is enough of this force often to punch (knock) tissues of clothes (clothing), to go deep into a skin on definite depth are termed as burnt grains. In thin cotton tissues of clothes (clothing) grains can abandon many small-sized foramens around of central bullet wound. At increase of spacing interval of a shot not burnt grains lose energy, do not piers clothes (clothing), are not sunk in a skin, but densely stick to them. At a shot from the lubricated weapons from a bore take off pieces of rifle oil. They also sit on an interrupting around of entrance hole in the shape of separate splashes at shot from a distance to 40-45cm. Near an initial foramen they are absent. On clothes the tracks of gun oil are well imaged at the maiden outrigger boom from lubricated arms, end as a rule, are not located or are much more gentle expressed at the subsequent shot. The tracks of oil find with the help of special exploratory methods (in ultraviolet rays). The detection of tracks of oil enables to judge mouth, in a definite measure about a distance and sequence of shot.

 

Distances (ranges) of a shot. It is so important to know for an investigator from what range the shot is discharged. The distance of a shot means a range between the muzzle of a firing gun and a target. Determination of this is based on appearances of additional factors of a shot around the wound. Ukrainian forensic ballistics considers that there are 5 such distances (ranges): contact, near contact, close (very close), near and distant (long).

A contact shot refers to a situation when a firing gun becomes into a full contact with the target therefore it is also called as a discharge without distance. A bullet track in a contact range shot is continuation of a barrel.

Two main expert signs may be revealed around entry wound: imprint of the muzzle (so called «schtanz-mark») upon the skin and appearances of all accompanying factors of a shot (burning, blackening, tattooing) are mainly present inside the wound canal.

 

 

The muscles around a bullet track are bright pink due to formation of carboxyhaemoglobin. The entry wound itself may be small and regular or large and irregular, depending upon the underlying structures. As, for example, the skin wound is large and ragged in head wounds where the gases may expand between the scalp and skull resulting in undermined, irregular and everted margins. They are usually star-like. Soot is frequently deposited on the underlying bone.

Contact shot – when a shot gun is fired with the muzzle in contact with the body. Under this a bullet channel is continuation of barrel. All of shot factors (projectile, gases, flame, not burnt gunpowder pieces, soot ) come into the wound. An imprint of the muzzle (tattooing) is created. It is a specific sign of contact shot. It is a damage of the skin in scratch appearance whether bruise around entrance of bullet wound hole reproducing constructive peculiarities of the muzzle.

The Stamp-impresses always are found in area of entrance hole and have in diameter 2-3 cm. The Zones can mask by laying on of soot and blood. That them to express, after describing of wound cautiously it is needed to wash and to wipe wound allotment. Impresses-scratch can be round, pear shaped with entrance hole in the middle. Scratch allotment at first moisture with red hue, then gradually gets dry and becomes dark. The Impresses-bruises of crimson-dark blue color, them contours not always pass on form and size of the muzzle. The Impresses-bruises dispose on distance 0,5-1 cm from edge of entrance wound. The Impresses-wounds are generated thinly, they small and not deep (to hypodermic base).

So, the main forensic appearances of contact shot are:

    Laceration of the surface skin

    Laceration of the deeper tissues

    Fragmentation of bones

    Scorching of the skin and hair

    Blackening around the wound

      Imprint of the muzzle

Description of entrance hole attached to shot closely depends also on properties of being subject cloths and allotments тіла.в which realizable shot. Contradistinguish such variants: shot into body allotments, where under skin is disposed a bone (head); shot into breasts whether stomach, where be subject cavity; shot into body allotment, where there is a thick layer of soft cloths (buttock, thigh, shoulder) and shot into small cavity (into mouth, into anal hole, into vagina).

If the bone disposed near under skin, then attached to shot closely powder gases do not able to come in by on the morrow of bullet into small hole, because they expand at the time.. All that rises by gases and rives by reason of turning inside out of wound edges. In tie with that a wound takes radiant shape, with slights tear on edges. Attached to comparison of break edges in wound centre appears a skin defect for counting of small rounded coulisses on pieces tops, sometimes the coulisses edges are thene, by reason of what a wound centre falls back.

The hole edges and clothes for motion of bullet channel are covered by soot raid. A Considerable amount of it is found on internal wound pieces surface, on external bone surface around entrance hole, on hard cerebral envelope, deeply in wound channel, sometimes – on internal surface of hard cerebral envelope and bone by exit hole. Saturated with blood pieces, specially on beginning of wound channel, acquire a scarlet color for counting of formation carboxyhemoglobin.

Attached to shot closely into breast or stomach, powder gases, broadening an entrance hole in skin, quite penetrate into cavities, where and display its considerable destroying action. Attached to it, exclusive of general shot signs closely, entrance wound more frequent small (0,5-0,8 cm in diameter), round or oval form, on her edges can be the shallow slights tear. Wound This with sides of pectoral or abdominal cavity always most, than her dimensions on skin, diamond form three-cornered, frequently indeterminate,. By reason of mechanical gases action take place the considerable injuries of internal organs, stowed with liquid, for counting of hydrodynamic effect. The considerable injuries of internal organs (lungs, liver, stomach, bowels, heart, spleens, etc.) are observed.

If muzzle arm end is put to part of body, where is subject a thick layer of soft cloths (seats, thighs, lumbar allotment), then attached to shot closely gases penetrate into wound channel, considerably widening it. An Entrance hole can be usual, without slights tear and exfoliating of skin. But soft cloths (hypodermic base, thewses) considerably situated on considerable extent, a wound channel ordinary has expansion pairshaped with considerable effusions of blood into his wall.

Attached to shot closely into small cavity (for example, into mouth) the basic injuries form for counting of bursting gases action. Take place the typical mouth corners breaks in appearance of radial wounds, cracks, numerous breaks of mucous envelope of mouth cavity, pecies of bone fractures of jaws top and lower. In bullet going out place are the big lacerated wounds, part of brakes of skull vault bone can be absent.

 

A near contact range shot: fire weapon is directed under an angle to the target and its muzzle is not pressed firmly to the object and the barrel comes into partial contact only to the victim due to its lateral angled position. Thus, accompanying components of a shot may be partially blown into the track taken by the bullet through the body and flame, powder grains, hot gases, metallic particles may be found on the skin surrounding the entrance wound. However, the physical imprint of the muzzle may occasionally be revealed around the entry wound. It must be noted, that an imprint of the firing barrel is not circular like in contact shot but it is incomplete (semicircular) only. So, general manifestations of a near contact shot are following: partial muzzle imprint (schtanz-mark) around the entrance wound, oval blackening and tattooing on the skin, bright red color of the soft tissues in the area of an entry wound (due to carboxihaemoglobin formation) and splitting of the skin in an entry wound.

 

 

 

Near contact shot  – shot from arm, which is disposed not perpendicularly to monkey-chatter, and under some corner, when to clothes or body leans only part of muzzle cut. Such shot has the shot signs closely and shot from lustily near distance. Attached to it destroying, action celebrates not only bullet whether fraction, but gases and flame. One. part of gases with their composing elements (by soot, not burnt particles of dust, metals grains) by on the morrow of bullet penetrate from wound channel, traumatizing a clothes, soft parts whether bone, and where them can be seen attached to research. Other part of gases directs outside entrance wound, and soot, the not burnt gunpowder corns cover clothes allotment whether skin, disposed on the part of open corner in the shape to oval. A Entrance hole localizes by expertise, by oval edge.

Typical sign of near contact  is arched impress muzzle of the end of arm from one wound (incomplete stamp-impress) side in scratch appearance by length 1-2 cm, by width 0,3-0,5 cm, or in bruise appearance of a little greater dimensions. A Incomplete stamp-impress is a sigot permanent, but if it is, then shot proof partially closely (or closely). As and attached to shot closely, one of shot signs partially closely presents color of soft cloths in allotment of entrance wound into scarlet by reason of formation carboxyhemoglobin from acid to carbon, that is contained in powder skunks.

On woven clothes materials by reason of shot partially closely arise the cruciform breaks of different size, breaks length bearing off from bullet hole, not identical. One whether two breaks considerably longer from the rest, they accord with open corner of leaned arm and always covered by soot raid, remainders not burnt grains.

 

A close shot. This is a shot within mainly the range of flame and hot gases actions to the target, so to say, within about 5-10 cm. from the muzzle. In other words, this is a distance of a shot when mechanical action of powder gases is still seen around the entrance hole. In general the common expert manifestations of entrance wounds at close shot range are the following: 1. Cross-like ruptures (splitting) of outer clothes and entry wound due to powder gases action; 2. Soot or blackening is due to fine carbon particles around the shot hole and can be readily wiped off the skin. Tattoo marks are fully distributed in surroundings and caot be wiped off. Blackening and tattooing are so extensively deposited around the entry hole. They are circular too. 3. Bright red color of the entrance wound (margins and bottom) due to chemical action of powder gases. 4. Singeing of outer clothes, hair and skin in the place when a bullet penetrates the body. 5. An abraded collar and dirt ring can be easily revealed.

 

 

Close distance is such distance, attached to shot from which powder gases and flame are still capable to entail damage of clothes whether to man body. For contemporary hand rifle arm this distance compose 5-10 cm no more from muzzle anus end

A Shot with very close distance are characterized by follow signs:

    Entry wound is circular

    Singed by flame

    Surrounded by soot

    Cross-like ruptures of the clothes or skin

      Burning around the wound

 

A near shot is that, within the range of a powder blast but outside the range of flame, therefore within about 30-100 cm. both in cases of rifled and shot guns. The deposit of soot and tattooing is spread out over a large area but there is no singeing of hair or splitting of the skin. Commonly, tattoo marks together with blackening or tattooing only (without soot) are seen at a near shot while other additional factors of a shot are absent in an entry fire wound.

 

 

 Near distance  is such distance, when a target is located within the range of gunpowder action but outside the range of flame. That is why only burnt grains of gun powder and soot (blackening) are found around the wound.

Under this an entrance wound has usual description. The soot of shot settles on impediment and can be expressed on distance to 30 cm, thinly –more, not burnt gunpowder corns – to 80-100 cm and even more, because they fly considerably further soot, as diminutive projectiles. Practically 100 cm is a boundary path of near shot distance (for smokeless gunpowder).

 

A distant (long) shot. In a distant shot, there is no burning, no soot, no tattooing. The wound is circular with inverted margins and may be of the same size or even smaller than the bullet due to the initial stretching of the skin. The edges may be slightly contused. The adjacent skin may be abraded and soiled, the fibres of the clothes may be turned in at the entrance. All rims are precisely seen in entry wounds.

 

 

In distant shot there aren’t any additional effects around the entry wound.

In this case additional shot (soot, particles of dust, metal grains) factors already do not fly so far, and that’s why do not appear. Distant shot for hand rifle arm, as a rule, starts to for boundary paths 100 cm, thinly – 150-200 cm.

When do not find additional shot traces, then in deductions show, that shot signs from near distance not expressed. A Lack of traces of near shot not yet bears witness to that it is done not from near distance. A Shot could be realizable, for example, on the strength of clothes, which is absent, on the strength of some gasket, on the strength of doors, which held out by man body from contrary side and T.i. y such cases traces of near shot remain on cloth, to gasket whether on doors. A Entrance bullet hole under this has the peculiarities incident to it.

 

Entry holes in distant shot

From laid out swims out exceptionally important clothes research sense, head-dresses, footwear attached to bullet wounds. The inquiring Results into them are included into basing of expert deductions. If corpse with bullet trauma got into morgue without clothes, it isnecessary to explore it addition.

Appears, that insignificant part of soot and other shallow parts goes on with flight together with bullet iearbullet and pustbullet to vortical spaces. Attached to bullet interaction with man body whether her clothes this mass is a party to procrastination on kneaded “soot” simulating a shot picture from near distance. Procrastinations of soot on unnear distance (to 1000 m) are conditioned by big bullet (more 500 m/sec)flight speed, targets (2-3 layers, thin, dense) properties and presence of small intervals between clothes layers (0,5-5 cm).

 

 

FIREGUN  INJURIES  OF  INTERNAL  ORGANS.

SMOOTH BORED FIRE INJURIES

 

A wound canal in firearm injuries. According to definite actions of a bullet to a human body 3 types of the wounds may be formed: tangential, perforating and blind (non-perforating). A perforating firearm wound consists of an entrance wound, wound canal and an exit wound. So, the path, passed by a projectile in a body is termed as a wound canal (bullet track). There are 3 zones in formation of the wound canal: a zone of initial destruction, a zone of a contusion and a zone of molecular shake. There are 4 types of wound canals: direct, indirect, intermittent and continuous. The direct continuouscanal passes all organs in one line. The intermittent canal is formed due to displacement of the organs. The indirect canal is formed as the result of collision of a bullet with a bone when a bullet changes its trajectory of flying. The intermittent indirect canal takes place when a projectile enters the cavity or hollow organ, passes the distance and comes out in the other place.

A track taken by the bullet through the body is also called as a bullet track. It should be described in relation to the planes of the body: 1. from front to back or from back to front; 2. from left to right or from right to left; 3. from above downwards (caudad), or from below upwards (cephalad). Angular estimation, i.e., vertical, horizontal and sagittal planes of the body are also useful to complete the description.

Firearm injuries of inner organs. Firearm injuries of parenchymatous organs are quite typical. A discharged bullet punches a hole and forms a vast linear track with great zone of destructed tissues filled with blood. An entry hole is round or oval, with radial ruptures and inverted borders. An exit hole is bigger in size, its shape is indefinite, it’s margins are irregular and everted. Firearm injuries of hollow organs are characterized by small entrance and large exit holes. The filled hollow organs may burst due to hydrodynamic effect of a missile.

 

 

 

Wound or bullet channel is a way laid by bullet (and by also pellets whether splinter) in body. This – the injuries in cloths or organs, disposed between entrance and exit holes, or between entrance hole and bullet whether pellets (attached to blind wounds). A wound channel is continuation of entrance fire wound. It form, size and properties are determined by kinetic bullet energy and cloths resistance, that push through. In majority of cases wound channel is bee-line. The channels are through going and blind, straight and not, single and numeral, continuous and broken, in with surrounding, closed and open.

Attached to through going bullet wound or pellets quite transfix all body whether his part (head, neck, finiteness). Attached to insufficient projectile energy it remains in body cloths,   sometimes under skin – blind wound. The Straight channels have appearance of bee-line. The not straight wound channels are generated, when a bullet pass over a little organs, which are able lightly change location or to change its regulation (on the strength of a little bowels loops, on the strength of different muscles groups,   on the strength of breasts with damage of heart and etc.), or when bullet, coming in into body and running on its way across dense tissue (bone, cartilage), changes its primary direction by reason of ricochet. Exclusive of numerous shot, the numerous channels arise and then, when a bullet is divided into little parts and each from them forms separate motion and separate exit hole. Continuous channel can be spied on all his extent from entrance to exit hole without any breaking, not looking at that it can pass over different cloths and organs (for example, in head – on the strength of skin, bone, brain matter ). Bullet while meeting the bone can go on its surface as if surrounds part of body and proceeds from contrary side – this is a surrounding channel. Such wound can perceive for through going penetrable. Counted higher wound channels are closed. A Bullet or pellets can go on surface over bodies, forming a groove wound in skin or even to omit an oblong scratch. Such channel is called open, and wound is tangent.

The wound channel consists of: the wound channel (central his part), to it joins a slaughter zone, which in living transforms in process of time into necrosis zone, and zone of culturally-molecular shock.

According to distinctions of different cloths and organs, a bullet way has its peculiarities, on which we and will come to a stop. Passing over flat bone (skull, sternum, pelvis), a bullet forms in it a hole, which expands into bullet flight side.

 

 

Exit and entry holes in the skull

Around this hole ordinary one can be found radial, and sometimes – concentric cracks. A hole made a hole by bullet has appearance of truncated cone, a small base of which is found with side, from which a bullet flew, and a big base indicates on that side, where bullet started to fly. This enables to emplace bullet entrance into body and bullet going out place from it, specially in research cases of bone, when the soft cloths absent, for example, rotted (attached to troupe exhumation, attached to exposure skeleton of the body etc.).

In epiphysis of long tubular bone from bullet wound hole wound channel is formed, in that time as entrance place of its round or oval form from almost by equal edges. In dialyses of long bullet flnitenesses bone brings, as a rule, on many pieces fracture. By bullet entrance Place into tubular bone will be that hole, which few lesser, has a round whether oval form, serrulate edge and from which cracks move away overwhelmingly radial. Hereupon on lateral bone surfaces exude the large splinters reminding of butterfly wings.

Bullet injuries of sufficiently dense internal organs (livers, kidneys, spleens, pancreas) in the main of the same type. A Bullet beats out part of tissue, forms a rectilinear wide wound channel, bringing on breaks of his walls with vast zone of separated and cloths rolled by blood. For holes properties ordinary one can be defined area of bullet flight.

Properties of bullet wounds of hollow organs depend on degree of their filling. While damage of empty stomach, vesica urinary or bowels bullet holes in them usually roundshaped with numerous short breaks serous and mucous envelopes (for exclusion of shot closely). Being borrowed into hollow organ, stowed with liquid or halfliquid by contents, a bullet creates a effect of explossion.

Firearm injuries of bones. Morphological manifestations of such injuries depend on type of damaged bones. Thus, in flat bones (skull, sternum, pelvis, scapula) the wound of entrance shows a punched –in (clean) hole in the outer table. The inner table is unsupported and a cone-shaped piece of bone is detached forming a crater that is larger than the hole on the outer table, and shows sloping surface. Fissured fractures often radiate from the defect. Generally, a perforating fracture is formed and a bullet track looks like a truncated cone dilating aside of a bullet’s flight. In tubular bones the missile punches a hole and a perforated-splintered fracture is formed. Commonly, the round or oval aperture with numerous radial fractures can be revealed on the entrance of a bullet. The large zone of fragmentation and destruction can be seen on the opposite side.

Direction of the bullet’s flight. The direction of the track depends upon the posture of the body at the time of firing. The direction of fire may be determined from the position of entrance and exit wounds and the track, bearing in mind the possibility of deflection of the bullet and the different relationships of the parts of the victim in movement.

If the bullet strikes the body at the right angle, the abrasion collar is circular and uniform because the scraping by the bullet is equal to all the sides of the wound. If a shell enters the body at an angle, the wound itself is round, but the marginal abrasion is oval or elliptical, due to increased width on the side of the entry according to the bullet moving across a wider surface of the skin on that side. Therefore, the direction of the bullet is from the wide to the narrow side. When the bullet enters the body from an oblique angle, one edge of the wound is shelved or undercut, which indicates the direction from which the bullet entered.

 

 

Smooth bored fire injuries

 

Forensic medical characteristics of shotgun injuries. A shot gun is a smooth bored firearm. It refers that the bore (inside of its barrel) is perfectly smooth. A special cartridge is used for firing. The shot gun cartridge has numerous lead pellets or shots (single spherical small balls) as its projectile. There are also some wads. When a weapon is fired, the pallets disperse soon after their exit from the barrel, and this dispersion can be controlled to some extent by a chocking device near the muzzle to make it more compact. The pellets together with wads fly out as a compact and uniform shell. Beyond the muzzle it dissipates on separate components. At the range of 10 m. from the muzzle the mass of discharged pellets is nearly 50-70 cm. in a diameter. The maximal range of fired pellets is 200 m. up to 500-600 m. Actions of accompanying factors in shotguns can be found on greater distances than in rifled weapons. In cases of shotgun injuries the same distances of a shot (as in cases of using rifled firearms) are distinguished: contact, near contact, close, near and distant which are characterized above. Generally, there are 4 main manifestations at shotgun injuries depending mainly on definite ranges of a shot: 1. The distance of a shot is not more than 0,5-1 m. from the muzzle to the target. Forensic medical features can be observed as the following: the entrance wound is huge (2,5-3,5 cm in diameter); the margins are serrated, ruptured and slugged. The wound track and adjacent tissues appear pink and muzzle imprint is present (in contact and near contact shots). 2. The distance of a shot is between 0,5-2,5 m. One main hole (but its size is smaller than in a previous case) together with separate pellet holes are found as typical expert appearances at such a shot. 3. The distance of a shot is between 1,5-5 m: a small central entry hole can be seen and dispersion of pellets are spread so vast around the hole. 4. The distance of a shot is more than 5-6 m: a central entrance wound is absent, dispersion of pellets is great, numerous pellet holes are observed on the target.

Exit shotgun wounds. They are small, spindle-shaped, multiple and separate. Their margins are usually everted as the unsupported skin is struck from within. All additional effects of a shot (tattooing, blackening, singeing) are mainly absent.

In forensic damage practice by fraction attached to shot from hunter arm meet prettily frequently. In majority of cases they lustily typical and do not bring on difficulties in their diagnostics. A pellets together with wad and other components of equipment of hunter cartridge under shot time takes off from gun trunk as compact projectile. Then under windage influence and other factors this projectile starts gradually to disintegrate into sides and to stretch into length, forming a cone with top, turn to trunk hole. On distance 10 m a fractional projectile already has a diameter of 50-70 cm and length to 1,3 m, then these parameters augment.

 

Smooth bored fire injuries of the chest

 

 

Action of additional shot factors displays on considerably greater distances, than attached to threaded arm, chiefly for counting of greater gunpowder mass. Powder soot can be expressed on distance up to 1 m, and separate gunpowder corns – to 2-3 m.

 

 

Smooth bored shot (hunting rifle, 2-3 m.)

Pellets during the flight disperses. And this fact has laws (specifically, by what further it flys, all the more so scatters and being borrowed into aim, occupies greater allotment). To define shot distance in such cases can still in linear measures.

 

Contact shot with hunting rifle – imprint of the muzzle

 

 

Different kinds of the entry wounds caused by hunting rifle

 

For comfort all pellets wounds variety one can be erected into four variants, shot distance of each pellet of depends on employed gunpowder appearance:

 

Dispersion of the projectile (pellets) according to some ranges

For more exact shot distance determinatioecessary experimental to reproduce a wound by dint of shot series by cartridges that, from arm that, from which a wound was entailed.

 

Wound caused by unmarried shot

 

Unmarried is called shot from firearm by cartridge, into which there is not projectile (bullet whether fraction). Shot by unmarried cartridge closely, partially closely or from lustily near distance can bring on terrible and even mortal injuries. Destruction cause in the main powder gases .

Form of entrance holes attached to shot into allotments, where near is subject bone, from distance 1-2 sm radiant from 3-10 by rays by length 0,5-4 sm. Shot by unmarried cartridge closely into head, the breasts whether stomach causes penetrable wounds. In skull bone mark numerous fractures with many pieces with defect to 2,4 x2,6 sm. In cerebrum form the deep wound channels by diameter 3-5 sm. On the chest are generated the ribs fractures with many pieces, in lungs – are observed the blind injuries by diameter of 5-7 sm with numerous parenchimal slights tear.

The certain  methods in investigation of firearm injuries

 

The positive and valuable results give such laboratory research methods, as immediate stereomicroscopy, photographing, in that number in infra-red rays, research of some objects by the medium of infra-red transformer, histological, X-ray examination, electrocardiographical, chemical methods, spectral analysis etc.

 

 

 

close shot (infra-red light)

 

 

GUNSHOT INJURIES

 

 

An understanding of gunshot wounds requires some  knowledge of the construction and mechanism of guns and the ammunition which they fire. Rifles and handguns, but not shotguns, have rifled barrels. The rifling consists of spiral grooves cut the length of the interior or bore of the barrel. When a rifled weapon is discharged, the rifling causes the bullet to spin around its long axis, like a spinning-top, and this  lends gyroscopic stability to the bullet in flight, increasing the accuracy of the weapon. Shotguns by contrast have a smooth  bore with no rifling and are designed to fire multiple pellets, although they can fire a single slug. Rifled weapons, their ammunition and the injuries they produce are discussed first.

Smooth bore weapons, or shotguns, their ammunition and the  injuries which they produce are discussed later.  Rifled weapons Handguns andrifles are the two most frequently encountered rifled weapons. Handguns, as the name implies, are designed to be fired from the hand and may be revolvers or auto-loading pistols, so called ‘automatics’. Revolvershave a revolving cylinder containing several chambers each of which holds one cartridge, whereas auto-loading pistols have a removable magazine storing cartridges with a mechanism for autoloading after each firing.

Revolvers do not have manual safety catches. Rifles are firearms with a rifled barrel designed to be fired from the shoulder, and there are many designs around this theme. Other rifled weapons used by the military include submachine guns, which are designed to be fired from the shoulder or the hip and are capable of fully automatic fire, and machine guns which are heavier weapons also capable of fully automatic fire.

The ammunition or cartridges, for these rifled weapons consists of a cartridge case within the base of which is a chemical primer, with a chemical propellant above and the bullet clamped on top. The word bullet comes from the French word boulette which means a small ball, reflecting the fact that original projectiles were small lead spheres, the musket ball. Rifles are either rim-fire, having the primer located in the rim of the cartridge case, or are centre-fire, having the primer located at the centre of the cartridge case. Rim-fire rifles produce wounds similar to those of low velocity handgun wounds. Rim-fire cartridges are used mostly in small-bore, low velocity weapons, both handguns and rifles, of .22 calibre.

When the trigger of the gun is pulled, the firing pin strikes the base of the cartridge case where the primer is located, causing the primer to explode and to ignite the propellant. The propellant burns to produce large volumes of gasses under pressure. The original propellant, or gunpowder, used in firearms was black powder but this is now obsolete and smokeless powder is used instead. The heat generated by the burning propellant causes the cartridge case, which is typically made of brass, to expand and seal the chamber against any rearward escape of gasses. The large volume of hot gasses forces the bullet out of the cartridge case and down the rifled barrel to exit the muzzle of the weapon. Bullets come in a variety of shapes. The simplest are made from lead alloys and are traditionally fired from revolvers and .22 inch calibre rifles. Other bullets have a lead core encased by a copper alloy metal jacket. In military ammunition this metal jacket completely encases the lead core – full metal jacketing. In hunting rifle and semi-automatic pistol ammunition the lead core is partly exposedat the tip of the bullet – partial metal jacketing.

 

Wound ballistics 

 

Ballistics is the science of the motion of projectiles and wound ballistics is the study of the projectile penetration of tissues. A moving projectile, or bullet, has kinetic energy proportional to its weight and its velocity squared (KE . WV2). The wounding potential of a bullet is directly related to its kinetic energy and since kinetic energy increases in proportion to increases in the velocity squared, it is high velocity projectiles which have the greatest wounding potential. The transfer of kinetic energy from the bullet to the tissues produces the wounding effect. If the bullet does not exit the body then all

its kinetic energy will be transferred to the tissues, but if it exits the body then only some of its kinetic energy will have been transferred. Wobbling and tumbling of the bullet as it passes through the body, bullet deformation and break-up, long wound tracks and passage through denser tissues are all

factors which influence the loss of kinetic energy and increase the wounding effect.

Bullets disrupt tissues by two principal mechanisms. Direct laceration of the tissues occurs as the bullet penetrates just as with any penetrating object. This is the main mechanism of tissue damage in low velocity gunshot wounds from such weapons as pistols, and the permanent cavity visible in the body accurately reflects the tissue damage produced by the bullet. The second mechanism of tissue damage is temporary cavity formation and occurs only in high velocity rifle wounds. The transfer of kinetic energy from these bullets is go great that they create a temporary cavity up to 30 times the diameter of the bullet at a pressure of 100 to 200 atmospheres over a time span of 5-10 milliseconds. The result is a small permanent cavity surrounded by a wide zone of haemorrhage and an even wider zone of tissue damage which may not be obvious on examination. Other mechanisms of tissue damage include shock-waves, travelling at the speed of sound, which may cause the rupture of gas-filled organs such as the bowel; the creation of secondary projectiles such as shattered bone fragments in gunshot wounds to the head; and the effects of discharge gases which enter the wound track and produce tissue disruption if there is hard contact between the muzzle of the weapon and the body at the time of firing.

 

Rifled gunshot wounds

 

A gunshot wound is a penetrating wound which leaves a skin defect where the projectile passes through the skin. As a general rule a gunshot exit wound is larger and more irregular than a gunshot entry wound due to the effect of bullet tumbling and bullet deformation. Characteristic of entry wounds, particularly from handguns, is an abraded margin which surrounds the skin defect and is a result of the forward motion of the bullet indenting the skin and grazing it at the time of entry. The abrasion ring appears reddish-brown but can darken to almost black with post mortem drying. An abraded margin is typically absent from exit wounds, aiding their distinction from entry wounds. However, an abraded margin may be seen occasionally around an exit wound when the skin has been ‘shored up’ by a firm surface, such as a wall or a belt, so that the everted skin margins of the exit wound are impacted against the supporting surface. High velocity rifle bullets tend not to produce an abraded margin but rather micro-tears, which are fine radiating lacerations around the edge of the skin defect, best seen with a magnifying glass. Lubricant and debris on the bullet surface is wiped off onto the wound edge and appears as a grey ring of bullet wipe, but this is often obscured by blood and is more frequently seen on overlying clothing. The presence of bullet wipe is an indication that the wound is an entry and not an exit wound.

As well as the bullet, other products of discharge of the weapon exit the muzzle and may deposit on the clothing, the skin or enter the wound track. These products of discharge include soot, unburned, partially burnt and burning grains of propellant, and hot gasses including flame, which is incandescent gas. Together the effects of these are sometimes termed ‘powder burns’, but the more precise terms which refer to the effects of each element are preferable. Deposition of soot is described as smudging; propellant grains abrading and embedding themselves into the skin is described as tattooing; burning of the skin and its hairs is described as singeing.

If the muzzle of the weapon is in contact with the skin at the time of discharge then it may leave a muzzle impression, which is an imprint bruise-abrasion surrounding the skin defect of the gunshot wound. The mechanism producing a muzzle impression is the passage of discharge gasses into the wound track with resultant billowing out of the skin against the muzzle. In these circumstances the stretched skin may lacerate leaving an irregular stellate entry wound. Gunshot wounds through the skull, ribs, sternum and pelvic bones may leave coned defects with a smaller hole on the entry side of the bony plate and a larger bevelled defect on the other side.

The appearance of a gunshot entry wound will depend upon the range of fire, and determining the range of fire from the wound appearance is of forensic importance. If the shot is from a distance then only the bullet will strike the victim leaving a skin defect, typically with an abraded margin or with micro-tears in a high velocity wound, and possibly a grey ring of bullet wipe. At close range, which is within a muzzle to target distance of about arms length or 3 feet (1 metre), the defining characteristic is propellant tattooing on the skin surface. This feature may be blocked by head hair or overlying clothing, although the propellant grains commonly penetrate one or two layers of thin clothing to embed in the skin beneath. Individual grains of gunpowder should be retained for laboratory analysis since they may indicate the type of ammunition and therefore the type of weapon used.

In contact wounds, when the muzzle of the weapon is in contact with the body or only a few centimetres from the body, all of the elements which exit the muzzle on discharge produce their effects on the wound. The edges of the contact wound are seared by gasses and blackened by soot and propellant baked into the skin, and this may form a broader seared blackened zone around the skin defect. Soot may be deposited in a wide zone around the wound. This soot deposit can be

easily wiped off if the wound is washed. Washing blood from the wound carefully using a spray of hot water without scrubbing, should wash off the blood but leave behind any soot deposit. In suicides, the hand steadying the muzzle of the weapon against the skin may show soot deposition on the radial margin of the forefinger and the adjacent surface of the thumb. If the weapon is a revolver then soot deposits may arise also from the cylinder gap (the gap between the revolving cylinder holding the ammunition and the muzzle) when products of discharge emerge in a fan-like pattern at right angles to the long axis of the barrel. Soot, propellant grains, gunshot residues from the primer and gasses including carbon monoxide, as well as fragments of overlying clothing, are forced into and along the wound track.

 

Shotguns

 

Shotguns have a smooth bore and are designed to fire multiple pellets, although they can fire a single slug. The calibre or internal diameter of the bore of a shotgun is measured by an archaic system of gauge. The gauge of a shotgun is the number of lead balls of the given bore diameter required to make up one pound weight. The most popular shotgun gauge is 12, which represents a bore diameter of 0.729 inches (18.2mm). Confusingly a shotgun with a bore diameter of 0.410 inches (10.2mm) is not described by its appropriate gauge but as a ‘four-ten’. At the muzzle end of most shotgun barrels is a partial constriction of the bore known as a choke, whose purpose is to restrict the spread of the fired pellets. Shotgun ammunition, or shells, differ in some design aspects from cartridges for rifled weapons. The cartridge case has a brass lower part, or head, containing the primer mechanism and overlying propellant, and above this is a tube, traditionally made of compressed paper but nowadays of plastic. This paper or plastic tube is closed at the top to retain the lead shot within. Lead shot comes in a variety of sizes which broadly fall into two categories, namely bird-shot, which is used for birds and small game, and buck-shot which is used for large game. The standard pellet sizes are designated by a numbering system, and an individual cartridge bears the appropriate number to indicate the size of shot within. Bird shot pellets range in size from 0.05inches to 0.18 inches in diameter. Buckshot pellets range in size from 0.24 inches (number 4) to 0.36 inches in diameter (number 000). By recovering a representative sample of the lead shot, determining the average weight and comparing this with a standard table, the size of the lead shot, a characteristic of the ammunition used, can be determined.

Ammunition in the form of single lead slugs is available and an improvised ‘home made slug’ can be produced by partially incising the shotgun shells circumferentially just above the brass head so that this line of weakness breaks on firing and the lead shot exits the barrel still within the otherwise intact cartridge. Although single round lead bullets fired from smooth bore weapons are generally obsolete, they are still used in 0.410 inch muskets for riot control in India. Within the shotgun shell the propellant and pellets are separated by plastic or cardboard wadding. When the shotgun is fired, these wads exit the muzzle and travel a short distance, sometimes up to 20 feet. At ranges up to about 8 feet the wadding may enter the wound but at greater ranges it impacts the skin adjacent to the wound to leave a wad abrasion. Modern plastic wadding forms a tube around the pellets which opens like the petals of a flower on exiting the muzzle and leaves distinctive petal mark abrasions around the shotgun wound or on the adjacent skin surface. The diameter of cardboard or plastic wadding recovered from a wound or crime scene gives an indication of the gauge of the shotgun used, and may give some indication of the ammunition manufacturer.

 

Shotgun wounds

 

In shotgun injuries the pellets rarely exit and therefore the wounding effect is the full wounding potential. Within increasing range, fewer pellets strike the target due to pellet dispersion, and the velocity of the pellets falls off rapidly due to poor pellet aerodynamics. As a result, the range of fire has a critical effect on injury severity in shotgun shootings. At ranges of 20 to 50 metres and beyond there is a uniform peppering of shot which is rarely lethal.

Shotgun wounds of entry have a skin defect and abraded margin and, depending upon range of fire, may show soot smudging, propellant tattooing, singeing from hot gasses and a muzzle impression as with gunshot wounds from rifled weapons. Shotgun wounds display other features reflecting the fact that they are produced by multiple pellets rather than a single bullet, and sometimes show wad marks from the cardboard or plastic wadding of the shotgun shell. Contact shotgun wounds to the torso appear externally innocuous with a circular defect approximating the weapon bore. A muzzle imprint is commonly seen and if there is loose contact or clothing between the muzzle and the skin then there is surrounding soot smudging. The large amount of carbon monoxide forced into the wound produces a faint cherry-red discolouration of the underlying muscle due to the formation of carboxyhaemaglobin.

Contact shotgun wounds to the head are extremely mutilating

due to the large amount of energy dissipated by the shot and the large volume of gas which enters the wound. The great majority of wads and pellets will exit and typically the cerebral hemispheres are eviscerated. The shotgun entrance wound to the head is easily identified by the large amount of surrounding soot, the seared and blackened wound edges and the radiating large lacerations. By contrast the exit wound is ofteot identifiable because of the disruption of the head and fragmentationof the skull. When the entrance wound is intraoral there are stretch lacerations in the naso-labial folds and at the margins of the mouth. Propellant tattooing indicating a close range shotgun wound begins at a muzzle to body distance of about 1 to 2cm and disappears at a range beyond about 1metre. Beyond this range the appearance of the wound reflects the spread of pellets and any impact of wadding. As the range increases the round skin defect develops scalloped margins (hence its description as a ‘rat hole’ wound in the USA), and then a few adjacent satellite pellet holes before a definite cuff of satellite pellets appears at a range of about 2 metres.

At greater ranges there is considerable variation in the pellet pattern depending upon the ammunition used, the degree of choke of the shotgun and the

actual weapon. The pattern of spread of the pellets is documented by photography, and measurements of the diameter of the spread are made ignoring aberrant outlying pellets, so called ‘fliers’. The peeled back petals of plastic wadding may produce a patterned abrasion, in the shape of a Maltese cross, around the wound with the wadding entering the wound at ranges up to 2 or 3 metres. At greater ranges the trajectory of the wadding deviates from that of the pellets so that it impacts the skin adjacent to the wound leaving an abrasion.

 Precise estimates of range of fire in shotgun injuries require a comparison of the wound pattern on the skin and clothing with test patterns made by firing the same shotgun with the same ammunition. If the pellets strike an intermediate target, such as a pane of glass or wire door-screen, before striking the victim then this will increase the dispersion of pellets making range assessment liable to error. The dispersion of pellets within a body as indicated by X-ray is always greater than that seen on the skin surface as a result of the ‘billiard ball effect’ produced by the pellets bouncing off each other as they bunch up on entering the body. Shotgun exit wounds are usual where the entry is to the head or neck but exceptional where the entry is to the trunk, unless the trajectory is tangential through the body or there is a contact wound in a thin person or with buckshot ammunition.

 

X-rays

 

X-rays of gunshot victims, both living and dead, provide valuable information and X-rays should always be performed in autopsies on gunshot fatalities if the facilities are available. X-rays identify any projectiles present and their location, or may identify projectile fragments if the bullet has exited. The path of the projectile through the body can be determined and often the type of ammunition or weapon used. Projectiles do not necessarily follow a straight line path in the body but may ricochet off bones, most commonly the inner table of the skull, or enter the cardiovascular system and embolise. If the bullet is intact then the exact calibre cannot be determined due to the magnification effects of the X-ray.

The presence of pellets generally indicates the use of a shotgun, although novel shot-containing ammunition is available for some rifled weapons. A ‘lead snow-storm’ comprising scores of lead fragments along the wound track as a result of fragmentation of a partial jacketed bullet is a diagnostic but not ubiquitous feature of high velocity rifle hunting ammunition. Military bullets are specifically designed not to break up in this way within the body but they may do so under some circumstances. With partial metal jacketed bullets, the jacket and core can separate in the body and the lead core exit leaving behind the jacket, with its important rifling marks.

Large shotgun slugs are distinctive with designs specific to the manufacturer. The components of some projectiles, such as aluminium jackets, plastic tips and plastic shot shell wadding, are poorly radiopaque and difficult to identify on routine X-rays. Bullet embolisation is uncommon but may occur within the arterial or the venous system. Arterial embolisation occurs when the bullet enters the heart or aorta and typically embolises to the legs. Venous embolisation occurs when the bullet enters a large vein such as the vena cava or a cerebral sinus and then embolises to the right heart or pulmonary arteries. Small calibre, low velocity projectiles such as a .22 calibre bullet or birdshot pellets are most likely to embolise.

 

Ballistics

 

Rifles and handguns, but not shotguns, have rifled barrels. The rifling comprises spiral grooves cut the length of the interior or bore of the barrel. The raised metal between the groves is the lands, and the calibre of a weapon is measured from land to land. When a rifled weapon is discharged, the rifling produces marks on the bullet as the bullet passes down the barrel. Some rifling marks have class characteristics indicative of the make and model of the firearm. Other markings have individual characteristics which reflect imperfections peculiar to a particular firearm, and may allow the identification of that specific firearm. The class characteristics of bullet rifling marks include (1) the number of lands and grooves, which are usually between 4 and 6 but range from 2 to 22. (2) the diameter of the lands and the grooves. (3) the width of the lands and the grooves. (4) the depth of the grooves. (5) the degree of twist of the rifling, that is the number of inches or centimetres of bore required for one complete rifling spiral. (6) the direction of the rifling twist, which is commonly a right or clockwise twist and less commonly a left or counter-clockwise twist.

 

The individual characteristics of bullet rifling marks include

 

(1) imperfections of the grooves, which are most readily seen in lead bullets as a result of the soft lead being pressed into the grooves. (2) imperfections of the lands, which are most readily seen in jacketed bullets because the copper alloy jacketing is harder. In a shooting in which a jacketed bullet has been used and the jacket has separated from the lead core, then it is the jacket rather than the lead core which must be recovered for ballistic comparison. Linking a fired bullet to the suspect firearm requires the comparison of the recovered bullet with a test bullet. The test bullet is obtained by taking similar ammunition and firing it from the suspect weapon. The rifling markings on the test bullet and the crime bullet are then compared using a comparison microscope. This type of microscope has a split field in which the crime bullet and test bullet rifling markings can be viewed simultaneously and the bullets rotated to align the markings. If the usually 26 to 28 inch (66 to 71cm) long barrel of a shotgun is sawn off to aid concealment of the weapon for criminal purposes, then the rough edges around the newly fashioned muzzle may leave marks with individual characteristics on the exiting plastic wadding, permitting a ballistics comparison similar to rifling marks. Cartridge cases also have markings with class and individual characteristics which include: (1) the type of breach block marking. (2) the size, shape and location of extractor marks (3) the size, shape and location of ejector marks. (4) the size, shape and location of firing pin marks. Fingerprints are rarely recovered from firearms but may be obtained from cartridge cases, which are necessarily gripped between the fingers when the weapon is loaded. Cartridges too small to retain useful fingerprints may have recoverable DNA..

 

Testing for gunshot discharge residues

 

The primer, which explodes on compression and ignites the propellant, is commonly a mixture of lead styphnate, barium nitrate, and antimony sulphide. The metals lead, barium and antimony are vaporised and exit the muzzle, to condense and settle on surrounding objects including the hands of the shooter. Bullet metals also may be included in these gunshot residue particles. Cotton tipped swabs moistened with either 10% hydrochloric acid or 5% nitric acid are used to recover residues from the hands of suspects. When taking the handwipings plastic gloves must be worn.

The 4 areas swabbed are the backs of both hands and the palms of both hands, and each area is swabbed twice. On the back of the hand, the radial aspect of the forefinger, the dorsal aspect of the thumb and the skin web between is swabbed. On the palm of the hand the palmar aspect of the forefinger and thumb together with the base of the forefinger and thumb and the skin web between is swabbed, or alternatively the entire palm is swabbed. The swabs are then analysed for traces of the elements lead, barium and antimony which characterise gunshot discharge residues. Flameless atomic absorption spectrometry (FAAS) is used to detect all three metals, and neutron activation analysis (NAA) can be used to detect antimony and barium only.

Both NAA and FAAS are quantitative elemental analytical methods which do not distinguish the source of the metals, so that false positives are theoretically possible. Barium is a common element found in soil and lead is a common environmental pollutant from motor vehicle exhaust fumes. An alternative analytical method is to recover the residues using adhesive material and examine them using scanning electron microscopy (SEM) and elemental dispersive X-ray analysis (EDAX), which can identify gunshot residue by its characteristic appearance as well as elemental content.

In practice gunshot residues are detectable in about 90% of people who have fired handguns, but only about 50% of people who have fired rifles or shotguns. It is not only the presence and quantity of the elements, but also their distribution on the hands which is evaluated.

Residues on the palms of the hands only may indicate a defence gesture, or alternatively the handling of a previously fired weapon. In cases of suicide, residues are often detected on the non-firing hand used to steady the muzzle against the body. Recently lead-free primer has been developed because of health and safety concerns about the accumulation of lead in the atmosphere in firing ranges. This novel primer contains titanium and zinc. Firing different ammunition in succession from the same weapon produces residues with a mixture of elements from the different primers and bullets used.

 

Gunpowder

 

Gunpowder is a generic term for any one of several low-explosive mixtures used as propellant in guns. The first gunpowder was black powder which is a mixture of saltpetre (potassium nitrate), sulphur, and charcoal (carbon) in the approximate proportions 75:15:10. The saltpetre was originally extracted from compost piles and animal wastes. The consensus is that black powder originated in China, and was being used in fireworks and signals by the 10th Century.

By about 1300 the Arabs had developed the first real gun, a bamboo tube reinforced with iron. Whether knowledge of black powder entered Europe by contact with the Mongols or the Arabs is unclear but the English medieval scholar Roger Bacon recorded its recipe in 1242 in a coded form of Latin. Black powder is relatively insensitive to shock and friction and has to be ignited by flame or heat. Its burning is a surface phenomenon so that the fineness of the granulation influences the explosive effect. The product of burning is 40% gaseous and 60% solid, the latter accounting for the large amount of whitish smoke produced. Beginning in the middle of the 19th Century black powder was supplanted by nitrocellulose-based propellants.

Nitrocellulose is manufactured by nitrating cellulose fibres from cotton or wood pulp using nitric and sulphuric acids. It is inherently unstable and burns by decomposing rapidly, forming hot gasses. By contrast with black powder, it produces almost all gas upon combustion, from which it obtained the name smokeless powder. Today most forms of gunpowder are either single-based, that is nitrocellulose alone, or double-based, comprising a combination of nitrocellulose and nitroglycerine.

Glyceryltrinitrate, or nitroglycerine, is a detonating or high explosive characterised by extremely rapid decomposition and the development of high pressure. It is an important ingredient of most forms of dynamite but is employed also in medicine as a vasodilator in the treatment of angina pectoris. Nitroglycerine is 18.5% nitrogen and contains sufficient oxygen to oxidise the carbon and hydrogen atoms in its molecular structure while at the same time liberating nitrogen. Nitroglycerine was first prepared in 1846 by the Italian chemist Ascanio Sobrero, but it was the Swedish scientist Alfred Nobel who invented dynamite in 1867. Nobel died in 1896 leaving the bulk of his fortune in trust to establish the Nobel Prizes.

 

INJURIES OF MEDICO-LEGAL IMPORTANCE

 

WOUND: (legal definition):’ breach of the full thickness of the skin (or lining of lip). This excludes abrasions, bruises, internal injuries and fractures! WOUND: (medical definition)’ disruption of the continuity of the tissues produced by external mechanical force’ INJURY: from the latin injuria (in- not, jus- the law). The term is often used synonymously with wound but can have a wider use, including damage to tissues by heat, cold, chemicals, electricity, radiation, in addition to mechanical force LESION: from the latin laesio (a hurt). Originally meant injury, now more widely applied to include ” any area of injury, disease or local degeneration in a tissue causing a change in its function or structure” TRAUMA – bodily harm with or without structural alterations resulting from interaction with physicochemical agents, imparting energy to tissues. May cause morphologically apparent damage (wound) or produce physiological imbalance (eg reflex cardiac arrest by neural stimulation) and secondary effects (eg thrombosis, infection, obstruction of tubular organs)

TYPES OF TRAUMA

Energy may applied to tissues in various forms : 1) Mechanical Force Blunt force trauma (BFT) -a moving object (KE) striking the body as in a blow -the moving body (KE) striking a fixed object or surface as in a fall BFT causes bruises, abrasions and lacerations Sharp force: knife tip or edge, broken glass, jagged metal – applied force is concentrated over a small area, requires little force to cut tissues Firearm; high velocity, small mass projectile 2) Thermal energy: heat or cold 3) Electrical energy: flow of current may cause localised burn if resistance is high 4) Atmospheric Pressure: high or low, in air or water 5) Radiation: particle or radiation 6) Chemical reaction with tissue releasing energy Mechanical Force may cause Impact, Angulation, Compression, Traction, Torsion, Shearing, Acceleration/deceleration (RTA) Different tissues have varying properties of Elasticity (tendency of stressed material to regain its unstressed condition Plasticity (tendency to remain in stressed condition) Viscosity (resistance to change in shape when stressed) Different tissues therefore have different elastic limits (tolerance limits or break points) and are vulnerable to different stresses. Skin has greater elastic limit than underlying fat and blood vessels making subcutaneous bruising more common than skin laceration e.g. torsion often causes spiral fracture of tibia, soft tissues undamaged compression often causes rupture of gas-filled lung or intestine, but muscle and skin undamaged Injury occurs when energy applied exceeds the elastic limits (or tolerance) of the tissues. Whether or not injury occurs following the application of energy, in whatever form, depends on Physical and Biological factors. PHYSICAL FACTORS

1) Degree of Force or K.E. applied: Force = Mass x Acceleration Kinetic Energy = 1/2 Mass x Velocity2 Energy depends on mass of weapon or projectile, but on the square of its velocity Crash energy = (mph)2 x 0.034 Stopping distance in feet 2) Area over which force is applied: -same force spread over larger area is less likely to injure at site of impact edge or tip of knife allows a great concentration of force applied edge of a plank is more damaging than its flat face heel of stilletto is more damaging than its sole Soft object deforms and flattens 3) Duration over which force is applied: longer duration allows tissues at site of impact to deform and dissipate the applied energy eg fall onto soft surface (increases duration and area of impact) seat belt stretching slows down the rate of transfer of kinetic energy to the body and spreads the area of impact over the trunk (c.f. forehead on dash) 4) Direction of application: Transfer of kinetic energy from weapon or projectile is incomplete with a glancing blow or exiting bullet (some wounding potential is wasted) and complete when the weapon or bullet come to rest on/in the body

 BIOLOGICAL FACTORS

1) Mobility of the body part Fixed parts absorbs all applied energy. Mobile parts are able to transform KE into movement 2) Anticipation and coordination e.g.-boxer rolling with a punch spreads out the duration of impact, catching a cricket ball, rolling with a fall 3) Biomechanical properties of tissue Different tissues have different strengths and weaknesses -skin is elastic and more resistant than underlying tissues (Bruise > Laceration) -blood vessels more resistant to compression than stretching -bone more resistant to bending than to torsion -hollow or fluid-filled organs sensitive to compression -brain (semi-fluid) more resistant to direct impact than rotational impact (–> shearing of nerve fibres) -bone and joint may transmit force to a weak point

CLASSIFICATION OF INJURIES

(1) Bruise (from Old Englis  h b rysan– to crush, O ld French b ruser-t o break Syn. Contusion, Ecchymosis Defn. “escape of blood from ruptured small vessels (vein, capillaries, arterioles) into the surrounding tissues” The resulting discolouration is seen through the overlying intact skin. Due to blunt force trauma. Site, shape, size, severity of bruising are very variable (2) Abrasion From L atin a b– from and r adere- t o scrape Syn. Scratch, Graze Defn. ” a portion of the body surface from which the skin or mucous membrane has been crushed or removed by rubbing” A superficial injury, not involving the full thickness of the skin, i.e. confined to epidermis/dermis. Due to (1) Direct impact: imprint (may reflect pattern of causative surface) or (2) Tangential impact: graze or scratch (may reflect direction of impact) Always occurs at the site of impact

(3) Laceration From Lati  n l acerare– to tear. Botanical term- irregular edges Defn. Full thickness tearing of skin or tissue due to stretching and crushing by blunt force Characteristics: Ragged edge, Associated bruising/abrasion, Tissue bridges Provides little specific information about the causal object (4) Incision F rom Latin i ncidere– to cut into. Surgical term incision with scalpel Defn. Clean division of the full thickness of skin (or other tissue) by a sharp-edged instrument. Characteristics: Clean cut edges, No associated bruising/abrasion, No tissue bridges. Incised wound is LONGER THAN IT IS DEEP. Provides little specific information about the causal object (5) Penetrating or Puncture Wounds Defn. Puncture is “a small hole made with a sharp point” ITS DEPTH EXCEEDS ITS LENGTH on the body surface. Due to a sharp/flat instrument, e.g. knife (STAB), a sharp/thin, e.g. needle (NEEDLE PUNCTURE) or a blunt/long/rigid, e.g. wooden stake (PUNCTURE) Shape and size of wound often indicate dimensions of weapon. (6) Thermal injuries Application of dry or moist heat :burns & scalds Cold injury (7) Electrical Burns Heat produced by electrical flow. (8) Firearm Injuries Small mass, high velocity projectile fired from gun.

 BRUISES

(Syn: contusions, ecchymoses) From O ld English b rysan– to crush and Old French b ruser-t o break Definition: leakage of blood from ruptured small vessels (veins or arterioles) into the surrounding tissues. Haemorrhage or bleeding is the escape of blood from any part of the vascular system. Haemorrhage can also be external, from a skin wound, or internal into a body cavity. Bruising is haemorrhage into the surrounding tissues. Bruising may be seen in skin, muscle or any internal organ. Petechiae– pin head size bruise < 2mm Due to BLUNT FORCE TRAUMA Moving object strikes the stationary body (blow with fist or weapon) Moving body strikes a stationary object (fall) pinching or squeezing Often associated with skin abrasion or laceration (the more elastic overlying skin may be undamaged) Bruising less often associated with incised or stab wounds which allow outward escape of blood from cut vessels EXTERNAL BRUISING

Superficial bruise rapidly appears at the site of impact. Bleeding in the subcutaneous tissue seen as discolouration through the semi-translucent skin INTERNAL BRUISING

Not visible at surface Deeper bruise in muscle or internal organ will not be visible through overlying fat and skin. e.g. neck in strangulation, fatal brain injuries, blows to chest & abdomen The site of bruising does not necessarily reflect site of trauma.

Bleeding into tissues may continue for some time after impact under circulatory pressure. Extravasated blood tracks along natural/traumatic planes of least resistance, influenced by gravity and body movement. e.g. blow on temple –> bruise on cheek fractured jaw –> bruising oeck fractured hip –> bruise on thigh Delayed appearance on body surface

Deep bruising may take upto 24 hours to appear at surface (come out). Re-examination of a body or live victim after this time may reveal bruises not initially apparent. Ultraviolet light may disclose an otherwise unidentifiable bruise. Breakdown of RBCs with time (haemolysis) eleases breakdown pigments which may spread outwards and stain the tissues over a wider area then the original intact red blood cells of the fresh bruise. Pigments may spread closer to the overlying translucent skin thus becoming visible on the surface a few days after injury.

DEGREE OF FORCE

Skin has greater elastic limit than underlying fat and blood vessels making subcutaneous bruising more common than skin laceration. Degree of force cannot be accurately deduced from the size of a bruise. Although heavy impact will generally cause a large bruise, severity of bruising depends on: (1) Anatomical site: over bony prominence (shin, cheeks), lax, vascular tissue (eyelid, orbit) fatty tissue (buttocks) will bruise easily. Escaped blood has room to accumulate in lax tissues. Resilient muscle of anterior abdominal wall rarely bruises (although there may be severe underlying visceral injury). Dense, tightly bound tissue, e.g. palms, soles, rarely bruises. Dense fibrous tissue physically restricts accumulation of blood. (2) Age Infants have loose, delicate, fatty tissues which bruise easily. Elderly: degeneration of vessels and connective tissue allows easy bruising (3) Obesity & Sex Obese individuals bruise more easily than lean due to a greater proportion of subcutaneous fat Females generally bruise more easily due having a greater proportion of subcutaneous fat than males (4) Disease of clotting “spontaneous” bruising (haemophilia, leukaemia and platelet disorders), some infections (meningitis), liver disease ( including alcoholism), vitamin C deficiency (scurvey), poor nutrition, medications (5) Skin colour black skin may mask bruising. UV light needed.

AGE AND COLOUR CHANGE IN BRUISES

-immediately DARK RED (the colour of capillary blood) -soon turns DUSKY PURPLE -subsequent colour changes very variable in timing and result from HAEMOLYSIS by enzymes and cellular products. Colour changes begin at the periphery and progress towards centre if large. Smaller bruises may change colour uniformly. Pigments, including bilirubin and haemosiderin are released from haemoglobin within degenerating red blod cells Subsequent colour changes: 1. BROWN

2. GREEN 4-5 days or more 3. YELLOW 7-10 days or more 4. STRAW

5. DISAPPEARS 14-15 days (range 1-4 weeks) A small bruise in a healthy adult may disappear in 1 week. A love bite (Hickey) may vanish in 2 or 3 days. N.B. The time course is very variable time course depends on adequacy of lymphatic and venous drainage, size and depth of bruise, anatomical site, age of person (v. slow in elderly) and general health Accurate dating of an individual bruise is difficult. Distinguishing FRESH from OLD is easier and often important, e.g. repeated assault, child abuse POST MORTEM LIVIDITY (hypostasis, livor mortis) The settling of blood into the lowermost blood vessels under gravity after the circulation ceases. Results in a pinkish discolouration of the skin in the dependent parts of the body. Blood vessels compressed by pressure of contact with clothing or supporting surface will not fill and the area remains pale (contact or pressure pallor). Lividity is sometimes confused with bruising. Distribution and pallor help to discriminate. Incision of the skin shows oozing of blood from cut, engorged vessels which can be rinsed away in lividity. Incision of a bruise reveals escape of blood into the tissues which cannot be rinsed away. Escape of blood cells and haemolytic pigments from vessels into the surrounding tissues due to putrefactive breakdown may be difficult to distinguish from bruising. POST-MORTEM BRUISING can occur but needs great force to produce small bruise. After death blood is under physical pressure only. There is only a passive ooze from blood vessels ruptured after death rather than the active extravasation under pressure which occurs in life. Most likely to occur within areas of post mortem lividity where blood is under greater physical pressure and over bony prominences where tissues may be crushed against the underlying bone, e.g. back of the head. SHAPE AND SIZE of bruises are very variable & poor indicator of causative object. Expansion and movement blur the outline. Some bruises inflicted with a small hard object, immediately prior to death may retain the pattern of the causative object. Rapid death will limit the extension and blurring of the outline which usually occurs under circulatory blood pressure. e.g. bumper, grille or headlight on pedestrian, neck ligature, blow over clothing or jewellery An associated imprint abrasion is more useful. CLASSICAL PATTERNS OF BRUISING

Patterned Intradermal bruise due to impact with a hard, patterned object with ridges/grooves. Skin over ridges is compressed and vessels remain intact. Skin forced into grooves and dermal vessels ruptured. The resulting accumulation of a small amount of blood, near the epidermis may demonstrate the obvious pattern of the causal surface (tyre, shoe tread, car bumper, clothing, gun muzzle) It is often useful to trace the outline onto an acetate sheet for later comparison. Finger pad bruises are round or oval, slightly larger than the finger tips due to outward spread of blood. Due to gripping by fingertips in forceful restraint Found on -limbs and face (child abuse), thighs (rape), neck (throttling (manual strangulation)), arms (forceful restraint or post mortem movement of the body Tramline bruising due to a rod shaped weapon or stick. Compression of vessels centrally, not usually damaged unless crushed onto bone. Traction causes rupture of vessels along edges of rod. A solid stick bruise is limited to the convexity of the body surface (remember that a soft body part such as a buttock will mould and flatten. A flexible strap or flex willwrap around the convexity producing a longer and often curved tramline bruise. Doughnut bruise due to a spherical object (cricket ball) Love bite (hickey) Not a bite. No teeth marks. Suction bruise caused by firm application of the lips against the skin, forming an air-tight seal, oral suction causing a shower of petechial bruises from rupture of numerous small vessels. Normally found on teenagers after the weekend! Also seen oeck, breasts in sexual assault. Must be human in origin. A similar appearance is seen between the dental arches of a true bite. Counter pressure bruises of bony prominences of shoulder blades, sacrum and back due to forceful restraint against wall/ground. More common in muscles than skin. Black eye (peri-orbital haematoma) fist blow to orbit fractured skull (R.T.A., gunshot) tracking from forehead bruise. Punching is directed at the upper body , especially the face Causes bruising, abrasion, laceration over bony prominences and teeth, fractured nose & face. Bruising or abrasion of knuckles due to throwing punches Kicking (or shod foot assault)

Stamping, jumping may reproduce the pattern of the sole Glancing kick may cause a scuffed abrasion Direct blow (swinging kick) may result in bruising, laceration or a curved imprint abrasion Typical target sites: face, neck, loin, groin, back, chest. Associated internal injury is often severe Bruising of Various ages:

suggests repeated assaults (child abuse, wife/husband beating, elderly (beating or poor balance), alcoholics Medical interventi  on

-sternal and cardiac bruising -bruising around needle puncture marks -pinching skin to test conscious level (butterfly bruise) N.B. Bruising usually due to Accident or assault; it is rarely self-inflicted (too painful and unimpressive!) ABRASIONS

(Syn: grazes, scratches) From L atin a b– from and r adere- t o scrape Definition: “a portion of the body surface from which the skin or mucous membrane has been removed by rubbing” (from the Latin ab– from ,and radere– to scrape). A superficial injury of the skiot involving the full thickness of the skin (confined to epidermis and papillary dermis, or body lining epithelium). Usually due to BFT, exception is a scratch 2 Types: 1) Loss or scraping of epidermis/dermis by TANGENTIAL FRICTION on rough surface (graze) or sharp point.(scratch) 2) Superficial crushing of epidermis/dermis caused by DIRECT IMPACT. More often seen in fatalities Many abrasions have both a vertical and tangential component. Abrasions are clinically trivial, although they are painful, bleeding/exudation is slight and leads to crust/scab formation. Heals without scarring (by re-epithelialisation). Abrasions are often associated with bruising and laceration FORENSICALLY VERY IMPORTANT. Often the most informative of all injures: Always reflect site of impact

Often indicate causative object/surface

Often indicate direction of impact

Assessment of age of abrasions is difficult. Post-mortem drying of abraded surface causes a golden yellow or reddish, leathery, parchmented appearance. 1. DIRECT VERTICAL IMPACT causes Crushing of epidermis The causative object may stamp its shape or surface pattern on the skin –> IMPRINT ABRASION e.g. Rope weave in hanging or ligature in strangulation Fabric weave of seat belt, clothes, whip Tyre tread in RTA Bite mark ( double crescent of spaced linear impressions) Fingernail impressions (crescentic) oeck in throttling, neck, wrists thighs and vulva in rape 2. TANGENTIAL IMPACT Due to a glancing (tangential) impact by a moving object against stationary body or the moving body against a rough stationary surface.–> scraping of epidermis due to friction against a rough or sharp surface. Stratum corneum and superficial epidermal cells removed, causing exudation of fluid. Deeper loss of epidermis may expose capillary loops in papillary dermis and cause bleeding Direction of impact can often be assessed: starting edge has bevelled descent; a series of parallel furrows indicate direction of sliding motion; finishing edge has tags of heaped epidermis e.g. R.T.A. -body thrown across road surface (gravel rash) Falls Assault with a rough surfaced instrument. Finger nail scratches (same sites as imprint nail marks but drawn across surface. Depth and breadth often useful for comparison with assailant) Dragging of dead/injured away from scene of crime. BITE MARKS

Teeth marks may be abrasions, bruises or lacerations, or a combination. Clarity depends on contour of part bitten and the force applied. Animal bite is deeply arched or ‘U-shaped’. Human bite is near circular or shallow oval Size -indicates whether inflicted by an adult or child Teeth may close down on flat surface but more often a block of tissue is drawn into the mouth. Results in suction bruise (hickey) between the dental impressions. Shape of resulting bite mark is affected by flattening on release. Human bite may present as a series of separate bruises with central linear abrasions or a continuous, curved line of bruising. The mark may represent only part of the dental arcade When fresh, may provide useful evidence of asssailant’s identity: Size and shape of dental arcade influenced by distinguishing features e.g. Missing teeth, Displaced teeth Allows comparison with suspect. Bruising due to individual teeth spreads out and blurs, causing progressive loss of definition. Early expert dental opinion and photographs required. Seen on breasts, neck, thighs, abdomen and vulva in sexual assault. Any site in child abuse. Fights, including sport (rugby, wrestling & football!) Self-inflicted (fabricated assault, psychiatric). Accessible!

LACERATION

From Lati  n l acerare– to tear. Botanical term- irregular edges Definition: Full thickness tearing of the skin (or other tissue) due to stretching, pinning and crushing of tissues by blunt force trauma. BLUNT FORCE TRAUMA by moving object or fall. Pinning, crushing and stretching forces result in splitting and tearing of tissues. Same type of trauma which causes bruising and abrasion but full thickness injury Typically over BONY PROMINENCES where tissue is pinned and crushed against underlying bone, e.g. scalp, eyebrow, cheek, shin A single blow may cause more than one laceration Soft tissue areas of limbs may be lacerated by a blunt projecting object which pulls obliquely against the tension of the skin causing stretching and tearing. Rolling/grinding movement of vehicle wheel strips and tears Lacerations are characterised by:

1). Ragged edges (torn apart), bulging fat, crushed hair bulbs 2). Associated Bruising and Abrasion of skin edges and adjacent tissue (BFT) 3). Tissue Bridges in depth of wound (intact nerves, vessels, tendons) A tangential component may give one clean-cut edge, other ragged, undercut or flap-like. CLINICAL IMPORTANCE

Often little external blood loss (except scalp) due to crushing and retraction of vessels. Associated internal injury/bleeding. Wound infection frequent (F.B.).Heals by scarring

FORENSIC IMPORTANCE

1. Shape and size not usually related to causal object 2. Trace evidence in wound (F.B.) 3. Rarely self-inflicted EXAMPLES

Crescentic/circular … round-headed hammer Y-shaped … metal rod Inside lips (trauma against teeth) … blow to mouth Flaying laceration … rolling/stretching of skin over limb in R.T.A. Perineum … rape Stellate … heavy vertical blow. INCISED WOUNDS

Syn: cuts, slashes From Lati  n i ncidere– to cut into. Surgical term incision with scalpel Definition: Clean division of the full thickness of skin (or other tissue) under the pressure of a sharp-edged instrument. An incised wound is LONGER THAN IT IS DEEP due to swipe action. Instrument is sharp-edged, such as: knife (linear, clean), jagged metal (irregular, jagged), broken glass CHARACTERISTICS OF AN INCISION~

– clean cut, everted edges – no tissue bridges or abrasion of margins – linear or elliptical shape, often gapes – often deeper at starting end – jagged if inflicted through loose, folded skin. Chop wound is a variant of an incision. Has clean-cut edges but an abraded margin due to inversion and friction against the sides of the wide blade on insertion. FORENSIC IMPORTANCE

Reflect sharp edge, not weapon type No trace evidence Profuse external haemorrhage and air embolism Danger to life depends on site and depth Incised wounds may be Self-inflicted, assault or accident. SELF INFLICTED

At sites of election (wrists, neck, cubital fossae, chest, abdomen, groin) Suicidal cut Throat: tentative incisions (left side of neck if right handed), one or more deep, sweeping cuts, down from the left, across the mid-line, up towards the right ear. Sshallow –> deep centrally –> shallow. Cut slopes upwards and backwards. Incision isusually through level of thyrohyoid ligament and may be down to spine! Repetitive nicks at the base of the wound (sawing). Bleeding is venous, loss of consciousness is slow. Air embolism may occur.

 OTHER SELF-INFLICTED INCISIONS

Fabricated assault – superficial wounds to head, left arm, chest abdomen, thighs. Parasuicidal mutilation – face, arms, trunk … low self-esteem ASSAULT INCISIONS

Compared to suicidal cuts, homicidal cuts: – lack the unhurried election of site. May be aimed, but many miss. – lie both higher and lower across neck – no tentative cuts, all are forceful and deepen rapidly – no repetition in same track – slope backwards and downwards – associated with ‘defence injuries’ to hands and arms ACCIDENTAL

INCISIONS

–         random pattern – usually single – often deep and forceful

–         PENETRATING WOUNDS

(Syn: Stab & Puncture wounds) Puncture is “a small hole made with a sharp point” Definition: Penetrating injuries caused by separation of the skin and soft tissues under the pressure of a sharp or blunt pointed instrument, the greatest dimension being its depth. ITS DEPTH EXCEEDS ITS LENGTH on the body surface. Often appear trivial externally (short incision or laceration) BUT often causes internal trauma and haemorrhage. Caused by thrusting of (or falling onto) 3 types of instrument (1) Sharp and flat, e.g. knife STAB (2) Sharp and thin, e.g. needle NEEDLE PUNCTURE (3) Blunt, long and rigid, e.g. wooden stake, spike, screwdriver, tooth PUNCTURE WOUND

PENETRATING – passes into but not through organ PERFORATING OR TRANSFIXING – from Lati  n p erforare, p er-t hrough & f orare– to bore passes through and through an organ STAB WOUNDS

Descriptors of penetrating wounds a) Damage to clothing (slashes, stabs through folds, blood flow & drip patterns, trace evidence) b) Site in relation to anatomical landmarks, midline, heel. c) Shape d) Alignment (horizontal, vertical, oblique) e) Size : length & width with edges opposed f) Direction :in 3 planes g) Depth h) Damage to tissues along track i) Effects : external & internal haemorrhage, pneumothorax, air embolism Adequate description may provide vital information about : 1) Type of weapon (c): usually a knife 2) Dimensions of the weapon (e) 3) Taper of blade (e) 4) Movement of knife in wound (c) 5) Direction of thrust (f) 6) Depth of thrust (g) 7) Amount of force used 8) Likely effect on victim (h, i)

WOUND LENGTH

A straight in and out stab wound is slightly shorter than the width of the blade due to stretching of the skin over the point of the knife on insertion and elastic recoil on withdrawal. Wound length and width must be assessed with the edges taped together because the wound is often shortened and widened into an ellipse by skin elasticity (Langer’s lines of tension) and underlying muscle tone. Wound length < blade width (1) stretching of skin over point on insertion and subsequent recoil on withdrawal. (2) tapered blade not fully inserted Wound length > blade width when blade does not pass straight in and out – entry and withdrawal at angle. “Rocking” of knife on withdrawal. Cutting edge extends wound length The best indicator of blade width is the shortest (least rocking), deepest wound (weapon fully inserted) SHAPE OF WOUND May indicate: (1)Cross-sectional shape of knife blade e.g. – Double-edged blade –> Slit with two sharp ends N.B. single edged knife may give similar wound due to clean splitting over blunt end – Thin, single edge blade –> Triangular slit, one sharp end – Thick, single-edged blade –> Slit with one sharp and one ‘fishtail’ end due to stretching & laceration over blunt edge Stab wounds are typically elliptical with clean cut edges and no bruising or abrasion of margins (incision) (2) Direction of insertion overhang of upper edge, bevel of lower edge N.B. The direction of the wound track through the tissues is assessed at post mortem, with the body lying flat on its back. The position of the internal organs is different in life, when standing, sitting and breathing. (3) Movement of instrument on withdrawal Small change in angle –> notch Twisting –> crescentic wound

WOUND TRACK DEPTH

< length of instrument if not fully inserted > length of instrument if fully inserted and body surface compressed e.g. abdomen, chest. A small penknife can perforate heart or abdominal aorta. DEGREE OF FORCE

Wound depth is a poor indicator of force applied Pressure required to penetrate is often slight with sharp tipped instrument Depends on sharpness of point, not of cutting edge. Sharp tip requires little force to penetrate, blunt tip requires greater force. Speed of weapon’s approach (F= 1/2 m v2): quick thrust penetrates skin more easily than slow, sustained pressure Bony damage is useful indicator of depth and implies significant force Most resistance offered by CLOTHES AND SKIN The compressed skin ‘gives’ suddenly, releasing the energy stored in the compressed skin and tissue (elastic reservoir). Once the skin has been penetrated, the blade slips easily through the underlying muscle, internal organs and uncalcified cartilage, without the need for further application of force. Analagy is stabbing a melon

Penetration of bone requires considerable force and may break the tip off the weapon. A quick stab requires less force to penetrate than a slow push. Forcible insertion may cause imprint abrasion or bruising of skin by the hilt of the knife. Rare, most often on chest Remember to consider counter-pressure by victim: falling or running onto instrument. The knife does not need to be supported rigidly if tip is sharp. Considerable force and determination required to remove knife from clothed body.

EFFECTS OF STABBING

Victim may not initially be aware of injury. There may be little or no external blood loss. Internal blood loss may be profuse and rapidly fatal or slow enough to allow time for medical treatment. Main effect is bleeding. The time taken to incapacitate the victim and what actions are still possible is very difficult to estimate. A stab to the heart may bleed profusely out into the confined space of the pericardium. If pericardial defect is small or does not communicate with the pleural cavity cardiac tamponade may result (200-450ml). Left ventricular wound may partially reseal, resulting in slow blood loss or spontaneous healing. Thin-walled right ventricle less likely. Great vessels do not re-seal. Rate of bleeding from stab wound to the lung depends on the size of vessels cut. Large pulmonary veins & arteries branch outwards from the hilum. Peripheral stab bleeds less and may seal if lung collapses. Pneumothorax may itself be fatal. Cut through bronchus may bleed and obstruct airways. Abdominal stab may penetrate major vessels, liver or spleen with rapid haemorrhage into the abdominal cavity. Stabbing to the head and face may allow penetration of bone in the region of the eye, nose and temple where bone is relatively thin. Pulmonary air embolism originating in a partially severed jugular vein may be rapidly fatal before much blood is lost. Severing a carotid artery or jugular vein results in rapid exanguination.

PUNCTURE WOUNDS DUE TO BLUNT INSTRUMENTS

Blunt instrument typically –> Irregular, split, laceration-like wound. Greater force needed to penetrate skin. Inversion of skin on entry causes abraded margin. Crushing and stretching of the tissues causes bruising of the margins. Shape may indicate cross section of instrument. e.g. Hayfork –> Elliptical Ice pick –> Round Wooden stake –> Cruciate Poker –> Stellate laceration File –> Triangular laceration Scissors –> Depends on degree of closure. ‘Z’. Animal tooth

ASSOCIATED INTERNAL INJURIES

Surface wounds may be informative but are often simply the trivial markers of lethal underlying injury. Head injury (separate lecture notes) by fall, blow or RTA Head is heavy, mobile and unstable. Scalp bruising and laceration common over bone. Skull deformed by impact. If excessive skull may fracture at the site of impact: linear, radiating, depressed, hinge, ring, contre-coup. Injury to blood vessels and brain may occur without overlying fracture. Analagy: blancmange (brain), wrapped in cling film (arachnoid), in paper bag (dura), inside a cardboard box (skull), wrapped in brown paper (scalp). Any layer may be damaged by impact (blow) or dropping (fall) Intracranial haemorrhage often follows head injury: Extradural– fracture tears artery~ – easily overlooked (concussion, lucid, coma) – immediate or delayed accumulation of blood – causes pressure on brain – amenable to surgical decompression Subdural – common in elderly, children, alcoholics – small bridging veins torn by trivial impact or rotation – may remain asymptomatic, partially healed and an incidental finding at autopsy Subarachnoid– natural (aneurysm rupture) or traumatic, -ass. with contusion, laceration of brain -or blow to side of neck -often rapidly fatal Brain injury

-may occur without fracture or intracranial haemorrhage -rotation & accel/decel. injury more damaging than direct impact against the fixed, immobile head -blow accelerates the head causing contusion at the point of impact (coup contusion) -fall decelerates the head causing more obvious contusion at the diametrically opposite point (contre-coup) contusion where the brain glides over the irregular, jagged contours of the skull. Analogy is box of jelly

Coup= Kick (head is accelerated) Contre-coup= Dropping the box (all contents decelerated) Typically a backward fall striking the back of the head (occiput) on the ground causes scalp abrasion, bruising or laceration with localised coup contusion at the occipital pole and more marked contre-coup contusion over the frontal and temporal poles where skull surface is rough. May also occur in a fall onto one side but not after a forward fall. Greater force may lacerate the brain Deep intracerebral haemorrhage may occur Widespread subtle microscopic nerve fibre (Diffuse Axonal Injury)injury is common due to shearing stress of rotational impact or deceleration Analogy is shaking or kicking a TV set Associated swelling (cerebral oedema) is often fatal by raising the pressure within the cranial cavity (raised ICP) squeezing and damaging vital structures. Facial injury

-accidents (RTA) -assault by punch, kick, blunt weapon -fragile facial bones susceptible to injury -bleeding into nose, mouth and sinuses often profuse, may obstruct air passages. Neck injury

-vulnerable area, access to vital structures such as the trachea, large vessels (carotid arteries, jugular veins) -sensitive major nervous conections and reflexes -cervical spine and spinal cord -incisions, stabs, blows and pressure very dangerous (air embolism) Chest injury

-heart, major blood vessels and lungs vulmerable to impact, compression and penetration -blunt impact of RTA is common multiple rib #’s prevent respiration pneumothorax, lacerated lung, heart. -lacerated aorta due to deceleration -site of election for stab and gunshot wounds with profuse haemorrhage into pericardial sac or pleural cavities Abdominal injury

-Abdominal skin injury is rarely seen, particularly if impact is over a broad area -Liver, spleen, kidneys, intestines are vulnerable to compression and laceration against the spine following the blunt impact of RTA or assault -Site of election for stab wounds with penetration of vascular organs such as liver, spleen, kidney, mesentery or major vessels such as aorta, vena cava with severe blood loss into the peritoneal cavity -Peritonitis may follow intestinal damage. Limb injuries

Common in many accidents (RTA), falls, assaults Fracture (#)(= a disruption in the continuity of a bone) Result of direct or indirect force, may be complete or incomplete closed (simple) or open (compound) transverse, longitudinal, oblique, spiral comminuted (more than 2 fragments) compression # of spine, 5th metacarpal (boxer’s #) depressed # of skull stress # pathological # in weakened, diseased bone (osteoporosis, malignancy) Fat embolism clusters of fat cells escape from within the central marrow cavity of a fractured bone or subcutaneous fat and enter the circulation via veins. Become entrapped in the small vessels (mainly capillaries) of the lungs or may pass through the lungs to block the capillaries of the brain, kidneys, heart and elsewhere. Pyrexia, skin rash, coma, renal failure. May be fatal. SURVIVAL TIME AND ACTING

CAPABILITY AFTER WOUNDING

Post-injury survival time is important in reconstructing events How long did the victim survive?

Was the victim still capable of fighting, resisting or fleeing?

Some injuries are incompatible with any significant survival, however fit or young the victim. Destruction of the brainstem or arch of aorta cause almost instantaneous loss of consciousness and rapid death. Multiplicity of wounds and involvement of the heart and brain are associated with a short postinjury survival period. The effects of injury to major nerves, muscles and joints, followed by bleeding and shock will ultimately incapacitate the victim. The time taken to do so, and what actions are still possible is very difficult to estimate. A suprising amount of activity is often reported following infliction of an obviously lethal injury. Many remarkable examples in the literature. Levy & Rao suggest that overall, 71% of stab wound victims and 49% of gunshot victims survive at least 5 minutes. The victim may not be aware of the injury initially. Pain is suppressed by the adrenaline response of “fight or flight” and vigorous activity may be maintained for a period of up to a few minutes when the will exists. Such activity will cease when physical factors such as blood loss lead to immobility, loss of consciousness or death. Main effects of injury are bleeding and shock. Will ultimately incapacitate the victim. The time taken to do so, and what actions are still possible is very difficult to estimate. Activity varies from staggering a few paces to running considerable distances or up flights of stairs. Estimation of survival period is almost impossible. Numerous variables exist. Fit young adult will survive longer and be capable of greater activity than an elderly, infirm individual. Extensive destruction of the frontal cerebral lobes of the brain may permit survival and activity before death occurs from associated brain damage and shock. A stab wound through the left ventricle of the heart may almost completely seal itself by contraction of the cardiac muscle around the defect. Survival of such a wound is common. Death will only occur if continued leakage of blood into the pericardial sac interferes with the pumping action of the heart (cardiac tamponade). A stab wound through the thin-walled right ventricle, atrium or coronary artery is unlikely to re-seal itself and will bleed out into the pericardium with fatal results. Wounds involving the great vessels of the thorax (aorta, vena cava, pulmonary arteries and veins) bleed profusely and offer no chance of closure. Arteries carry blood at higher pressure than veins of similar size and therefore bleed more rapidly when cut. A partially transected vessel is less likely to seal off than one which is cleanly divided. The victim may remain alive for several hours with internal blood loss in excess of 2 litres. Consciousness may be maintained despite internal blood loss of 1.5 litres. The rate of blood loss is an important factor. An incised wound on the neck involving a jugular vein may prove rapidly fatal before much blood has been lost. The cut vein may draw in air which then forms a fatal air-lock (air embolism) in an artery supplying the brain. Stab wounds are typically slit shaped, allowing the possibility of closure of the wound due to skin and soft tissue elasticity. For this reason external blood loss is less profuse than from the gaping defect of a gunshot wound at the same site. Acting capability and survival time do not appear to be influenced by the degree of alcohol intoxication. INTERPRETATION OF WOUNDS

(1) Causative object or weapon Imprint abrasion from direct impact with patterned surface Trace material in sliding abrasion, laceration Stab may indicate shape, width, length of instrument (2) Order of Infliction Tentative or scattered FIRST Fatal or grouped LATER Distant shots before close shots (3) Manner of infliction By assessment of Circumstances, Scene of death, Pattern of injuries as a whole SELF-INFLICTED:

Gunshot wounds and ncised or stabbed wounds with sharp or pointed object. are preferred Blunt force injuries are rarely self-inflicted. Accessible target sites (often unilateral with “handedness”) e.g. incisions to wrists, cubital fossae, neck, groins stabs to chest (precordium), abdomen (epigastrium) shots to mouth, temple, heart Clothes drawn aside Multiple, Shallow, Tentative “Hesitation wounds” e.g. incisions to wrist and neck stabs to chest and abdomen Closely grouped, Parallel, Same Direction e.g .”sawed” incision in same track stabs at same angle partial withdrawal and reinsertion One or two potentially fatal Scars from previous attempts More than one method tried

ASSAULT:

Any type of wound (abrasion, bruise, laceration, incision, stab, gunshot) frequently in combination Punching -directed at upper body , especially the face. Causes bruising, abrasion, laceration over bony prominences and teeth and fractures of nose of facial bones Kicking-stamping, jumping –> pattern of sole glancing kick –> scuffed abrasion direct blow –> bruising, laceration. May also see a curved imprint abrasion Sites: face, neck, loin, groin, back, chest. Associated internal injury is often severe Sharp force is favoured -stabs & incisions – Any site – often inaccessible to victim, e.g. back! – Usually multiple – Wounds aimed at vital area but scattered and grouped A single wound suggests the victim was sleeping, drunk, drugged or incapacitated. The single wound is usually targeted (stab to heart, shot to head) – Lack the unhurried site of election – no time to chose – Inflicted through clothes – More uniform force – Multiple directions e.g. of incisions or stabs – Several may be potentially fatal – Associated defence injuries Defence injuries- a pattern of injuries sustained by taking protective action against anticipated trauma (accidental or assault). Indicates that victim was conscious, not completely suprised by attack and at least partly mobile. Typically seen on hands and forearms. Bruises, abrasions, incisions, stabs, gunshots Absence does not exclude assault (surprised) Secondary injuries due to falls onto nearby objects

ACCIDENTAL

Any type of wound, any site, usually single Clothing involved, defence and secondary injuries common. The Road Traffic victim

1) Pedestrian

Most vulnerable road user. Particularly children & elderly. The dynamics of the crash depend on the relative heights above the ground of the impact site and the centre of gravity of the pedestrian. Impact below centre of gravity throws victim onto bonnet (or roof at greater speed). Victim acquires velocity of vehicle only to be thrown onto the road surface by violent braking. Impact at C of G shunts victim in direction of travel Impact above C of G throws victim under vehicle Primary injurie  s are due to direct impact of vehicle against victim. -Car bumper injury to lower leg, if fixed by weight bearing (bruise, abrasion, laceration, fracture). The height of injury above heel of shoe is important. -A high fronted van will hits the thigh. -Flat fronted lorry or bus hits torso. -Primary injuries may harbour trace evidence (paint, metal) of evidential value in ‘hit and run’ collisions. Secondary injuries are due to impact against the bonnet, windscreen, road surface or other object/vehicle. -Bonnet & windscreen frame may fracture skull or injure chest & abdomen. -Thrown onto the road injures head, chest, abdomen —> Typical sliding abrasions, lacerations. Running over results in flaying lacerations to the limbs. Speed of impact cannot be estimated from the severity of injuries. Can only state whether injuries were mild, moderate or severe. Skid marks offer the only objective evidence of vehicle speed. Speed of impact % Fatalities

19-24 mph 10% 24-30 mph 47% 31-36 mph 73% 50% of fatalities are hit at speeds less than 30 mph. 50 % of those serious injured are hit at less than 21 mph 2) Vehicle occupants Occupants move towards the point of impact. There are 5 mainpatterns of impact: 1-Head on into a stationary object like a tree, another vehicle (speeds and impact energy additive) The driver and front passenger may strike -dashboard, windscreen & pillars (skull & brain); -steering wheel (chest-lacerated lung & heart); parcel shelf (# knees & pelvis) pedals trap the ankles -rear passenger hits seatback or over into front -deceleration causes whiplash (flex/extension) neck, DAI brain injury and ruptured thoracic aorta 2-Rear impact -speeds subtractive -seats and head restraints support torso and neck -whiplash (extension/flexion) with no restraint -risk of petrol fire 3-Side impact -direct -risk of side intrusion -Left: limb, spleen, L kidney, lung -Right: limb, liver, R kidney, lung 4-Side swipe -glancing -less risk of side intrusion 5-Roll over -less damaging (rolling spreads the time of impact) unless occupant is ejected Seatbelts

Extremely effective in reducing mortality and injury in low to medium speed impacts: -diagonal strap restrains upper torso (prevents impact with steering wheel, upper dash) -horizontal strap restrains lower torso and pelvis, (prevents impact with lower dash, parcel shelf) -area of straps spreads deceleration force over a wider area than localised impact -stretching of strap fabric increases the time over which the decel. forces are spread -prevents ejection through windscreen or burst door Seat belt injuries are common -bruising across chest & abdomen -neck injury and carotid artery rupture -fractured sternum, ribs, clavicles -lacerated mesentery, bowel -lumbar spinal injury Rarely more damaging than if a seatbelt is not worn. Other safety features

-airbags -crumple zones absorb impact energy and increase the duration of impact -laminated windscreens deform without shattering and prevent ejection -side impact bars -burstproof door locks to prevent ejection -padded steering wheel and collapsable column -breakable controls and mirrors 3) Motor Cyclist High speeds, unstable, no protection, difficult to see. Primary impact injury may be to leg. Secondary head, neck, chest and abdominal injury Helmet and leathers provide the only protection. Energy must be dissipated by sliding or rolling along the road. Contributory Factors in crashes Intoxication-alcohol, drugs, carbon monoxide. Human factors- reckless, speeding, inattention, fatigue, inexperience, shoes. Environmental- fog, rain, ice, snow, leaves, sun, obstruction to vision. Mechanical failure-tyres, brakes, steering. Natural disease-Ischaemic heart disease, stroke, epilepsy. Usually warning symptoms give enough time to pull over. BURNS AND SCALDS

Extent of heat-induced injury depends on 1. the applied temperature 2. the time for which the heat is applied 3. the ability of the body surface to conduct away the excess heat 5 hours at 4°C or 3 seconds at 60°C will cause a burn Heat may be applied by Conduction from solid, Convection from liquid or gas,Radiation -absorption of infra-red Burns (dry heat) Classification of severity (Wilson) FIRST DEGREE – erythema & blistering. Split in epidermis or at epi/derm junction painful due to exposure of nerves no loss of dermis capillary dilation, swelling and exudation blister, surrounded by zone of hyperaemia. Blister resorbs or bursts. re-epithelialises, no scarring. SECOND DEGREE destruction of the full thickness of skin not painful as nerves destroyed epidermis coagulated or charred central necrosis surrounded by zone of hyperaemia or FDB central area sloughs, epidermis grows in from edges and from epidermis in surviving dermal structures (sweat, hair follicle) underlying zone of tissue is precarious, may necrose if hypoxia or infection supervene. scarring centrally. Contractures may occur less painful than FDB Skiormally prevents water loss, regulates body temperature and prevents infection. Burnt skin loses salt-rich fluid from the circulation, resulting in low blood pressure (shock) and renal failure. Correction of fluid deficit is main initial aim of treatment. Swelling of burnt skin may result in touniquet effect on venous return and eventual arterial obstruction and tissue ischaemia and necrosis. Skin of limb or chest may need to be incised to relieve pressure. Infection often occurs and prevents skin grafts from taking. Rule of Nines indicates clinical prognosis: each arm is 9% of body area, leg 18%, anterior trunk 18%, back 18%, head 9%. Palm is 1%. Involvement of 30-50% of body surface usually unsurvivable (less in elderly, more in children) THIRD DEGREE

destruction of underlying fat, muscle, bone. When application of heat is prolonged the tissues may be charred, carbonised or completely destroyed. Dead body may show wide variation in severity from reddening tocomplete destruction of a body part. Post mortem burning obscures ante-mortem burns. Blisters will have collapsed with shreds and sheets of white epidermis over an angry red base. More severe burn –> stiffened, yellow-brown leathery skin due to partial carbonisation. PM drying of exuding skin –> parchmented surface. Skin surface often blackened by soot deposition. Hair ‘clubbed’ by melting and re-solidifying, or completely burnt away. Skin may ignite with subcutaneous fat burning as a fuel, clothes as a wick. Underlying muscle becomes pale, brownish (part-cooked). Max. effect with prolonged exposure – slow cooked muscle underlying intact skin. Deep muscle dehydration and denaturation causes PM contracture; the flexor groups more powerful –> ‘pugilistic attitude’. Intense, prolonged heat may destroy all soft tissues. Even bone may be reduced to brittle, grey-white splinters. Spurious wounds appear e.g. heat fracture, heat haematoma (extradural), skin splits Scalds (moist heat) Injury by hot liquid -water, steam, oil, other. Not accompanied by charring, carbonisation or hair singeing as seen in dry heat. Resemble first degree burn -red, desquamation, blistered. Intensely red base covered by wrinkled, macerated epidermis. Swelling and exudation of serum. Scald sharply demarcated by limits of contact with hot liquid. Immersion (relatively long period of contact with liquid) -> uniform area of injury with a horizontal fluid level, though irregular if splashed Tipped or splashed – Momentary contact, falling away under gravity with rapid cooling. Injury occurs in short period of time, necessitating very hot or boiling liquid. Liquid runs under gravity –>trickle pattern. Areas of initial contact most severely scalded. Infection may supervene. Death most often the result of shock, fluid and electrolyte disturbance.

ELECTRICAL MARKS

Severity of tissue damage depends on voltage applied and its duration, resistance of tissues and the current which flows. Body must form part of an electrical circuit so that current flows from an entry point to an exit point if injury is to occur. The path taken from entry point to exit point depends on the relative resistance of possible exit points. Takes shortest route between entry and best exit point. Entry and exit on same hand may cause severe burn. Shock may be fatal if current flows across a vital part of the body, e.g. hand to opposite foot, across heart causing ventricular fibrillation (VF). across chest –> respiratory muscle paralysis through head –> cardiac & resp. centre paralysis 240 V entering finger, through carpeted, upstairs wooden floor (poor earth, low current flow) gives painful spasm. 240 V entering finger, through wet, ground level, concrete floor (good earth, high current flow) potentially fatal. V = I x R, and I = V/R (Ohm’s Law) Alternating current (AC) is more dangerous than Direct current (DC) as it is more liable to cause cardiac arrhythmia. DC used in defibrillator to revert to sinus rhythm. AC of 40-140 Hertz or cycles per second is most dangerous. Domestic mains supply is 50 Hz. Current Injury depends on quantity of electrical flow ( Amperes, or more accurately, Coulombs, the product of amps x seconds) 30 mA applied to hand –> painful muscle spasm 40 mA –> unconsciousness 50-80 mA for > few seconds –> often fatal. Voltage Considerable voltage must be applied to dry skin to cause flow of 50 mA. Voltages of 24 or 100 Volts may be lethal if applied for long time. Very high voltage may be paradoxically safer as muscle contraction caused by shock may physically fling subject off the source. 240 V applied to hand may cause forearm muscle spasm, gripping the source and prolonging contact. Resistance The skin is the major barrier to electrical current, having very high resistance. Burns occur when current flows due to energy transfer to heat. Once inside dermis, current flows more easily through electrolyte-rich cytoplasm and blood vessels. Resistance of dry skin : 1000 000 Ohms, wet skin : 1200 Ohms. More current flow for given voltage. The electrical skin mark

The electrical mark is a type of localised thermal burn due to heat production when current flows through highly resistant skin. Seen at point of entry, usually hand, and exit or earthing point. There may be no skin mark, even in fatality. If the skin is damp or the area of contact is wide (less resistance per unit area) then the heating effect is proportionately less Firm contact with conductor Passage of current heats up tissue fluids to produce steam which splits skin within epidermis or epidermo-dermal junction. When current ceases the blister collapses to produce a raised white or grey ring with a depressed centre. The mark may reproduce the shape of the conductor e.g. linear wire or shaped metal object. Loose contact (narrow air gap) Current leaps the gap as a spark. 1000 V will leap few millimetres across dry air. 100 kV will leap 35 cm. Very localised point of entry creates a very high temperature causes melting of epidermal keratin which fuses into a slightly raised, hard browodule on cooling (the spark lesion). Arteriolar spasm causes a surrounding areola of skin blanching around the central blister. The peripheral zone outside the blanched area may be hyperaemic. Lesion may thus appear as Blister-Redness-Pallor-Redness from centre outwards. Smaller marks may appear as tiny white discs (epidermal split with no pallor or hyperaemia) Prolonged contact with domestic supply (usually after death) may cause severe burning with a wide area of epidermal peeling, hyperaemia and deep charring and cooking of muscle. High voltage transmission cables may cause similar deep burns or multifocal spark lesions (crocodile skin). Copyright 1999 – Dr D W Sadler.

 

 

 

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