FORENSIC BALLISTICS

A firearm is any instrument which discharges a missile by the expansive force of the gases produced by burning of an explosive substance.

Forensic Ballistics is the science dealing with the investigation of firearms, ammunition and the problems arising from their use.

General make-up and Mechanism: Firearms consist of a metal barrel in the form of hollow cylinder of varying length, which is closed at the back end and is called the breech end; and the front open end is called the muzzle end. The inside of the barrel consists of three parts. (1) The chamber, at the breech end to accommodate the cartridge, which is usually of large size than the bore, (2) the taper, called lead or leed in rifled arm and chamber cone in a smooth bore, connects the chamber to the bore, and (3) the bore, which lies between the taper and the muzzle. A breech action is attached to the barrel at the breech end to close the end of the barrel. It consists of a receiver which contains a bolt or block which closes and locks. The bolt or the block can be opened to insert a fresh cartridge into the chamber. When the weapon is closed for firing, the barrel comes into position against a flat block of metal called breech face, which seals the breech end of the chamber. The block is pierced in its centre to accommodate the firing pin which is actuated by a spring and moves forward when trigger is pressed. When the weapon the weapon is cocked (ready to be fired), the hammer has been pulled back against a b spring and is held back by the end of the sear, which rests in a notch known as the bent. When the trigger is pulled, the sear is disengaged from the bent and the hammer moves forward and strikes a small pushrod (firing pin or striker). Occasionally, the firing pin and hammer are external and can be pulled aback of the bolt action. The barrel of a “breakdown” action gun or rifle, i.e., a weapon which opens like a shotgun, has at its breech end a moveable limb called extractor, which moves backwards withdrawing the cartridge, when the breech is opened. In a bolt action weapon, a small claw fitted to the front end of the bolt, pulls out the cartridge with it, when the bolt is withdrawn. The lock contains the lock and trigger mechanism, i.e., the apparatus for discharge of the weapon. A firearm s provided with sights with which one can aim, so that the bullet can strike the target accurately. The ‘stock’ is the supporting or handle part of the weapon, the end of which is the ‘butt’. Usually the trigger mechanism and any provision for reloading and ejecting cartridges is within the stock. The hand –arms are provided with grips for grasping them by hand. In long barreled weapons, the butt is elongated to fit into shoulder. Those with long barrels are fired from the shoulder, i.e., rifle and shotgun, and those with short barrels may be fired from the hand, i.e., pistol and revolver. Firearms except revolves and hammer guns have a safety device, which locks the firing mechanism when it is applied, known as safety catch.

 

Classification : (I) Rifled weapons: (1) Rifles: (a) Air and gas-operated rifles. (b) 0.22 rifles. (c) Military and sporting rifles. (2) Single-shot target-practice pistols. (3) Revolvers. (4) Automatic pistols. (5) True automatic weapons (machine guns).

(II) Smooth-bored weapons (shotgun). (1) Single barrel. (2) Double barrel. (3) Slide-action. (4) Bolt-action. (5) Semi-automatic. (6) Automatic.

 

Rifled Arms: The bore is scored internally with a number of shallow spiral “grooves”, varying from two to more than 20, the most common being six, which run parallel to each other but twisted spirally, from breech to muzzle. These grooves are called “rifling” and the projecting ridges between these grooves are called “lands”. Riflings vary in number, direction, depth and width. When the bullet passes through the bore, its surface comes into caontact with the projecting spirals which give the bullet a spinning or spiraling motion. Rifling gives the bullet  a spin, greater power of penetration, a straight course and prevents it from unsteady movement as it travels in the air. Micro-groove system of rifling consists of 15 to 20 round grooves in bore of the barrel. Rifled firearms are divided into : (1) Low velocity (up to 360 metres per second). (2) Medium velocity (360 to 750 m/s). (3) High velocity (900 m/s and above).

Caliber or gauge: It is measured by the internal dimension of the barrel and is given in decimals of inch or millimeters. The dimension of the rifled weapon is measured between lands and not grooves. In smooth-bored weapons, the bore is measured similarly up to 1.27 cm. (0.5 inch). For larger bores, the size is determined by the size of the lead ball which will exactly fit the barrel, and by the number of such balls of equal size and weight as can be made from 454 gm. (one pound) of pure lead. Thus the 12 bore gun is one whose diameter is that of a ball of lead of such a size that 12 balls may be made form 454 gm. The smaller the number of gauge, the greater the diameter of the barrel.

Shotgun: It maybe single-barrelled or double-barrelled, the barrels lying side by side, or occasionally mounted one over the other. It is intended for firing a single ball, slug or a charge of shots. The barrel varies in length from 55 to 72 cm. The common gauges are 12, 16 and 20. the weapon is made to ‘break’ or open on hinge across the breech facing for the insertion and extraction of cartridge cases. Muzzle loading guns are loaded entirely from muzzle end with the help of a rod using gunpowder, pieces of cloth, stones, metal fragments, seeds, bolts, wood, screws, etc. The interior of the barrels is smooth. When the entire barrel from breech to muzzle is of the same diameter, it is called cylinder-bore. In choke-bore, the distal 7.5 to 10cm. of the barrel is narrow. Different degrees are known as full-choke, half-choke and quarter-choke or improved cylinder. Full-choke is the highest degree of bore constriction. Shotguns may have variable choke adapters. In most of the double-barrelled guns, left hand barrel is choked to some degree, the right hand barrel remaining a true cylinder. Double-barrel shotguns may have a different choke in each barrel. The choking lessens the rate of spread of shot after it leaves the muzzle, increases the explosive force and increases the velocity. There are some shotguns which have small portion of their bore near the muzzle end rifled, which are called “paradox guns”. Some shotguns have the whole of their bore rifled with very shallow grooves. An LG shot fired from a shotgun with a muzzle velocity of 240 metres per second, will have wounding power up to 180 metres. A musket is a military shoulder arm. It has a long forestock and usually takes a bayonet at the muzzle. It is smooth-bore weapon, e.g., 0.410 musket. 0.410 musket fires a single shot at high velocity and is effective up to 90 metres. The muzzle velocity of shotgun is about 240 to 300 m/s and of 0.410 musket from 350 to 600 m/s. Shotguns are effective up to 30 to 35 metres.

Cartridge: A cartridge is the complete round consisting of the case, the percussion cap, the propellent, the wad and the shot charge. The shotgun cartridge consists of a case of short metal cylinder which is continuous with a cardboard or plastic cylinder. The case is rimmed, which helps to keep the cartridge in correct position in the chamber, and makes extraction easy. The case helps to keep the various components in place, prevents the backward escape of the gases and provides a waterproof container for the gunpowder. The length of the cartridge varies from 5 to 7 cm. The cartridge case is filled as follows from the base: percussion cap (detonator cap; primer battery cup), which is set into the centre of the base of the cartridge cylinder, gun powder, a thick felt-wad with cardboard discs lying in front and behind it, the shot and finally the retaining cardboard disc. The diameter of the wadding used in the cartridge is greater than that of the bore of the gun. Wad acts as a piston and seals the bore completely, thus preventing the expanding gases from escaping and disturbing the shot charge. Wads may be glazed-board, straw-board, plastic, cork, felt, etc. Weds may be disc-shaped, cup-shaped, or bizarre-shaped. Shots are of two types (1) Soft or drop shot is made of soft lead, (2) Hard or chilled shot is made from lead and hardened by antimony. The shots may also be plated with copper. The shot consists of up to several hundred small lead shots. The number depending upon the size of the individual pellets. “Shot size” is expressed in number. The smaller the number, the larger the shot. Dust-size shot gun pellets number up to 2600 minute shot in 12 bore cartridge. Birdshot is generally used for hunting fowl and very small animals. The shot are small, ranging in diameter from one to 3.5mm. A 12 bore shotgun shell contains 200 to 400 shot. “Buckshot” has a diameter of 6 to 8 mm. In a 12 bore shell they are nine in number. Rifled slugs are single projectile, and are used in shotguns for big game hunting. They are similar in shape to a blunt bullet with a deep hollow cavity in the base. The sides commonly have angularly inclined fins or ribs that resemble very coarse rifling marks on bullet. The slugs are usually a little smaller in diameter than the shotgun bore itself. The slugs have much greater range than pellets. The spiral grooves on the slugs impart spinning effect. The felt-wad contains grease, which lubricates the bore after the firing of each round. The modern one piece plastic wadding tends to have greater range due to its greater weight. The powder is protected from the grease wad by a thin grease-proof card-wad. The card-wad behind the shot charge prevents the shots from getting lodged in the felt-wad. Some cartridges contain ‘power piston’ which holds the shot inside a polythene cup, which may contribute to the wound at short range. Some cartridges may have brightly coloured plastic granules as a filler between the shot, which may be found inside the wound.

Improvised firearms or country-made firearms are common in India. They are of various calibers but 12 bore is the commonest. They are usually smooth-bored. Some of them can be mistaken for factory-made guns, but others do not appear to be guns at ll. Walking-stick guns and folding guns are single-barrelled shotguns.

Rifle : A rifle is a gun with a long barrel, the bore of which is rifled. A carbine the bore of which is a short-barrelled rifle, or a musket. Its barrel is less than 55 cm,. in length and is meant for persons on horse-back./ it may be self-loading or automatic or both. It is effective up to 300 metres. The bore of a rifle varies from 5.6 to 7.7 mm (0.22 to 0.303 inch). It has a magazine and bolt action, muzzle velocity 800 metres per second and can kill at a range of 3,000 metres. The longer barrel gives an increased speed to the projectile. Velocity is the speed of the bullet or projectile at a predetermined point in its flight. The pressure in the fireing chamber is about 20 tonnes per square inch. The bullet as it leaves the barrel, rotates at about 3,000 revolutions per second. The muzzle velocity is 450 to 1500 metres per second. Rifles may be single-shot, repeating, semi-automatic and automatic.

The four common basic types are: (1) Slide-action rifle (pump-action or trombone-action). The slide on the underside of the barrel is moved manually backward and forward to extract and eject a fired case, feed and load a fresh cartridge into the chamber and cock the gun. (2)  Bolt-action rifle: It is manually operated in which the bolt and its handle function to open and to close and also lock the breech. (3) Lever-action rifle: The lever located beneath the receiver or frame is manually moved in swinging and pivoting downward motion and then returned. This acts through a linkage system to open, extract and eject the spent cartridge from and close and lock the breech block. (4) Semi-automatic rifle: Its operation is similar to the semiautomatic pistol.

Revolver: Revolvers are so-called because the cartridges are put in chambers in a metal cylinder, which revolves or rotates before each shot, to bring the next cartridge opposite the barrel, ready to be fired. It has a cylindrical magazine situated at the back of the barrel, which has a revolving motion, and can accommodate 5 to 6 cartridges, each housed in a separate chamber. In the single action type, cocking of the hammer rotates the cylinder and brings the cartridge in the proper position for firing. In the double action type, the hammer can be cocked by hand, or by a prolonged pull on the trigger. The muzzle velocity is 150 to 180 metres per second. They are low velocity weapons. The effective range is 100 metres.

Automatic Pistol: It is a hand arm in which the cartridge is loaded directly into the chamber of the barrel. When a cartridge is fired, the empty cartridge case falls on the ground several metres away, and a new cartridge is fired, the metres away, and a new cartridge slips into the breech automatically by a spring. The cartridges are contained in a vertical magazine n the butt, which can accommodate 6 to 10 cartridges. They are really semi-automatic or self-loading, because the trigger has to be pressed each time a round is fired. The bores vary from 6.35 to 11.25 mm. (0.25 to 0.45 inch). The muzzle velocity is 300 to 360 metres per second or more. They are high-velocity weapons. Their effective range is about 100 metres.

Air Rifle and Air Pistol: In these, compressed air is used to fire lead slugs. Some weapons use cartridges of liquid CO₂ as the propellant. The velocity is very little and usually minor injuries are caused. Their range is about 40 metres. The missile is single and fired through rifled barrel. The bores vary from 4.4 to 5.6mm. Wounds are rarely fatal, except when the head is struck. The slug can enter the skull and pass through the whole mass of the brain, but does not produce an exit wound.

Pen Guns: Tear gas pen guns may be modified so as to fire oridinary artridge.

Zip Gun: It is a crude home-made single shot rifled firearm.

Stud Gun: They are tools used to fire metal studs into wood, concrete and steel.

Automatic Weapons: Machine-guns or sub-machine guns continue to fire through the action of gases of the previous explosion and of the ejector and recoil spring.

Cartridge: It consists of a metal cylinder with a flat base which projects as a rim except in an automatic pistol. Rimless cartridge has an extractor groove near the base. The primer cup (percussion cup) is fitted in a circular hole, usually in the centre of the base and has a flash hole in the centre which communicates with the powder space inside. The metal cylinder or cartridge case is elongated, and its distal end tightly grips the base of the bullet. The gunpowder lies between the detonator and the bullet. Usually there is no wad, but sometimes one piece wad is kept. Low-power rim-fire cartridge may not contain gunpowder but only a primer compound in a hollow rim. As such, those cartridges cannot produce the tattooing. Many bullets have near the base, a circumferential groove called “cannelure”, into which the end of the case is crimped. A bullet without cannelure is held in position by stabs on the circumference of the case.

Primers: Primers are ignited by impact (percussion) of the gun’s firing pin. Centrefire rifle and pistol primers are small metal cups usually held in place in the cartridge head primer pocket by friction. The primer cup contains the priming mixture and an anvil so placed that the blow of firing pin on the primer cup crushes the priming mixture against the anvil centre and burns it, which then flashes through the flash hole (fire holes or vents) in the centrefire case head, and ignites the powder charge. The primer used in shotgun cartridge is called a primer battery cup. This consists of a battery cup into which a primer cup fits. The battery cup supports the anvil and provides a flash hole. It is also held in place by friction. The priming mixture contains lead peroxide, lead styphnate, tetrazene, barium nitrate, etc. In rimfire cartridges no percussion sup is provided. The priming mixture is contained within the hollow rim of the cartridge and ignited when it is crushed between the rim walls of the cartridge head b the impact of the firing pin.

Powders:

(1) Black Powder: It consists of potassium nitrate 75%; sulplure 10%; and charcoal 15%. It is designated as FG, FFG, FFFG, etc., depending on the size of the grains. The more number of Fs, the finer are the grains and the faster in burning. The powder grains are black, coarse or fine, without any particular shape. It burns with production of much heat, flame and smoke. Fine grains travel 60 to 90 cm. or more. One gram of powder produces 3,000 to 4,500 c.c. of gas. The gas consists of CO, CO₂, nitrogen, hydrogen sulphide, hydrogen, methane, etc., all at a very high temperature.

(2) Smokeless Powders: It consists of nitrocellulose (gun cotton), or nitroglycerine and nitrocellulose (double-base). They produce much less flame and smoke and are more completely burnt than black powder. One gram produces 12,000 to 13,000 c.c. of gases. The colour varies from bright organe to bluish-black, and in shape from minute globules, flakes, square, rectangular, irregular discs, cylinders to longer threads. Semi-smokeless powder is a mixture of 80% of black and 20% of the smokeless type.

Bullets: The traditional bullet is made of soft metal and has a rounded nose. The metal is lead with varying anmounts of antimony added to provide hardness. This is known as the round-nose soft bullet, and is usually used in rifles and revolvers. The caliber of a bullet is its cross-sectional diameter. in revolver and pistol,  the bullet is short and the point usually round or ogival. In rifle, the bullet is elongated with pointed end. Variations are: (1) Square-nosed, soft metal bullet, known as “wad-cutter”, and used primarily for target shooting. (2) Hollow-point variety has a depression in the nose of the soft metal. This bullet is designed to expand or “mushroom’ upon impact.

Jacketed bullets are of two types: (1) The full metal jacket bullet in which a tough, heavy jacket covers all but the base, where the soft metal interior is exposed. The tough jacket may be made of steel, copper, nickel and zinc. (2) The semi-jacketed bullet is provided with a relatively thin but tough jacket, which covers the base and the cylindrical portion of the bullet, leaving the nose partly or fully exposed. This type is designed to expand or “mushroom” like the soft metal, hollow-point type. The combination of the above two is also available. Mushroom bullets produce more serious wounds. Other types of bullets are (1) Short flat-point. (2) Medium flat-point. (3) Medium round-nose. (4) Long round-nose. (5) Medium long sharp-point. (6) Medium sharp-point. (7) Flat base. (8) Sharp-point boat-tailed. (9) Pencil-point. (10) Streamlined with sabot.

The flat base is the most common. In boat-tail bases, the base tapers to the flat with a profile, much like the rear portion of a boat. Rifle bullet weights range from 2 to 33 grams. A dumdum bullet is open at the base, and has the point covered with the jacket. When it strikes an object, the lead at the point expands or mushrooms, and produces a large hole. Expanding dumdum bullets, where the tip of the jacket is cut off, fragment extensively upon striking, and produce extensive wounds with ragged margins. A bullet with a hole in the point is called hollow-point or ‘express bullet. Incendiary bullets contain phosphorus.

Explosive Bullets: The exploding bullet is of various types. The common type has a cylinder  inserted into the tip of the bullet. The cylinder contains either black powder or a detonator, such as lead azide. The cavity may contain a single lead shot and possibly a percussion cap and a tiny primer anvil. The wound produced is larger than the usual. If the missile explodes. There is greater fragmentation of the bullet and increased destruction of the tissues. The surgeon and pathologist should wear goggles and use long-handled instruments to manipulate the missile during surgical operation or autopsy, as they are vulnerable to detonations of explosive missiles. The removed bullet should be handled with long rubber-covered forceps and kept in a padded container to protect it from excess impact, vibration and heat.

Plastic bullets: Buton round (plastic bullet) is a solid cylinder of polyvinyl chloride (PVC), 38 mm. in diameter, 10 cm. long, weighing 135 g. It is fired from a smooth-bore weapon and is effective up to 50 to 70 metres. They are used for riot control. It should not be fired at a person under 20 metres range. It causes bruising and pain. Fracture of the skull, eye damage, fracture of ribs, limb bones, and contusions of liver, lung and spleen have been reported.

Mechanism of Discharge of Projectile: A firearm is fired when the trigger is pulled, which is usually situated below, or below and behind the breech. The trigger releases a pin or hammer, whose tip strikes the percussion cap at the base of the cartridge, which explodes by heat created by the strike of the firing pin and sends a flash through a tiny hole into the main body of the powder-filled case, which sets fire to the powder charge or propellent, producing instantaneously a large amount of gas which is under high pressure. The cartridge case swells outwards, due to which the hold on the bullet is released, and forces the bullet into the barrel. Simultaneously, the cartridge case is pushed backwards with equal force against the breech face. The bullet passes out. The confined gas behind it gives recoil thrust to the gun. Noise of gun firing is caused by muzzle blast, or due to the suddenly released gases disturbing the air. If the velocity of the bullet is more than the speed of sound, then there is also a crack from that. The bullet reaches its maximum velocity as it comes out at the open end of the barrel and this is called muzzle velocity. The bullet is followed by a blast of highly compressed hot gas, particles of partially burnt and unburnt powder, smoke, flame and fragments of metal, cartridge and detonator, grease and wad or disc matter. The blast has the shape of a cone whose apex is located at the muzzle. All these things produce some effect on the body at short ranges.

Mechanics of Bullet Wound Production:

(1) Bullet Velocity: A bullet’s ability to wound is directly related to its kinetic energy (E=mv²/2) at the moment of impact. Because kinetic energy increases in direct proportion to weight (mass) of the missile and the square of its velocity, a bullet traveling at twice the speed of a second bullet of equal weight and similar shape, possesses four times much energy or wounding power. Tissue damage produced by high velocity a bullet is disproportionately greater than that produced by bullet of ordinary muzzle velocity. A wound produced by a bullet, whose impact speed equals its muzzle velocity is more severe, than that produced by the same bullet, discharged from the same gun, whose speed has been reduced due to traveling a long distance before it strikes it s target.

(2) Tissue Density: The greater the tissue density, the greater is the amount of energy discharged by the bullet’s passing through it. A bullet may cause slight damage to the soft tissues, but the same bullet at the same speed can produce extensive comminution of the bone.

(3) Hydrostalic Forces: Hydrostatic forces cause excessive degree of destruction. When a bullet passes through a fluid-distended hollow organ, e.g., food-filled stomach, urine-filled bladder, CSF-filled ventricles of the brain, or a heart chamber distended with blood in diastole, produces extensive lacerations due to the explosive displacement of the liquid in all directions.

Wounds from shot guns:  The flame extends upto 45 cm; Smoke upto 30 cm; and unburnt and partially burnt powder grains upto 60cm; cards upto 2 metres and wad for 12 to 15 metres.

1. Contact wounds: They are usually round or oval, large, often ragged because of gas tearing. The margins are contused. As the gases are blasted within the wound, the subcutaneous and deeper tissues show severe disruption. The smoke, flame, carbon particles, and wad are driven to some distance through the wound. If contact is loose or if clothing is interposed between the end of the barrel and the skin, the skin adjacent to the perforation exhibits fouling. Contact wounds on the head are associated with greater disruption of the margins and often show linear tears in the skin extending from the margins of the main wound. Extreme mutilation is caused due to the explosive effect of the gases. A large irregular hole is produced in the skull with fissured fractures running from its margins. There is localized pink discolouration of skeletal muscle due to carbon-monoxide.
2. Close Range Wounds: Within a distance of about 15cm, the pellets strike the target as a tightly knit mass and produce a single defect, circular or oval usually 3 to 4 cm. in diamer. The margins of the skin wound may be clean cut or slightly ragged. The deeper tissues show marked disruption. The skin surrounding the defect is blackened by smoke and burnt by flame. Unburnt particles of powder are embedded in the skin, producing tattooing, powder stippling or peppering. Carbomonoxide may be present in blood and the damaged tissues.
3. Intermediate Range Wounds: at a distance of 60 to 90 cm. single irregular circular aperture 4 to5cm. in diameter with irregular and lacerated edges is produced. The shots are scattered after entering the wound and cause much damage to the internal tissues. At a distance of 1.5 metres, the shot mass enters the body in one mass, producing a round defect. The margins are abraded. At a distance of 2 metres the shot mass begins to spread. The wound of entry is irregular, with ragged margins (rat hole), about 5 cm. in diameter, with a few satellite perforations at the margins of the main defect. At a distance of 3 metres the central aperture is surrounded y separate openings in an area of about 6 to 7 cm. wads enter the body. No fouling.
4. Long Range Wounds: At a distance of 4 metres and above the shots spread widely and enter the body as individual pellets producing separate openings in an area of 10 cm. in diameter. With small shot the individual pellet entering the skin produces round defects with narrow marginal abrasions. Wads usually cause circular nonpenetrating abrasions of skin. At a range of 20 metres or over the pellets only penetrate the skin or muscles.
5. Exit wounds: They are usually absent except in: (a) Contact wounds of the head and trunk. (b) Tangential wounds where some of the pellets have a very short track through the body. (c) Wounding of a thin part of the body, e.g., the neck, or extremities. (d) Wounds produced by large caliber buck shots or rifled slugs.

At contact or near range, greater disruption of tissues occur than is seen in entrance wounds. The margins are everted but there is no singeing, blackening or tattooing of the margins. There may be small separate wounds made by individual pellets.

Wounds from Rifled Fire-Arms: The flame extends upto 7.5cm, smoke upto 30cm, and unburnt and partially burnt powder grains upto 60cm.

1. Contact shot: The discharge from the muzzle, i.e., gases, flame, powder, smoke and metallic particles are blown into the track taken by the bullet through the body. The wound is large and crateriform in type and triangular, stellate, cruciate, or elliptic due to expansion of the gases. The margins are contused, abraded and everted. There is no burning, blackening and tattooing around the wound. If the contact is loose, burning, blackening and powder residue will be seen on the skin surface. Head wounds show as very large explosive type of injury with bursting fractures. The skin wound is large and irregular. The opening is cruciform with ragged and everted margins. Fissured fractures often radiate from the circular defect in the skull. The muscles around the track of the bullet may be brightpink due to carbonmonoxide. The bone fragments pass through the bone as secondary missiles.
2. Close Shot: Within a range of 7.5cm. the entrance wound is circular, about the size of the bullet with inverted edges and is surrounded by blackened, singed and tattooed area. the margins are abraded and contused due to the rubbing of the gyrating body of the bullet against the inverted epidermis. This is called “abrasion collar” and “contusion collar”. A black coloured ring “grease or dirt collar” may cover the abraded collar due to the bullet lubrication.
3. Near Shot: Within a range of 45 to 60cm. the entrance wound is circular, and smaller than the size of missile. The margins show blackening and tattooing. Abrasion and contusion collar is present.
4. Distant shot: The wound is smaller than the bullet; circular and margins are everted. Burning, blackening and tattooing are absent. Abrasion collar and grease collar are present.

Interpretation of abrasion collar: (1) When bullet enters at right angle to surface, abrasion collar is of uniform width. (2) When bullet enters at a tangent to the surface, abrasion collar is of an irregular width and widest border indicates the direction of the bullet.

Skull: In the skull, the wound of entrance shows a punched-in hole in the outer table and the opening on the inner table is large and shows beveling. Pieces of bone from wound of entrance are often driven into the cranial cavity. At the point of exit, a punched-out opening is produced in the inner table and beveled opening on the outer table.

1. Exit Wounds: They vary in size and appearance. When the weapon is fired in contact and close range, the exit wound is usually smaller than the entry wound. With high velocity bullets the two wounds may be of same size. The edges of the exit wound may be puckered or torn. It is usually larger than entrance wound due to deformity of bullet or secondary missiles (i.e. bone)

Peculiar effects of Fire-Arms:

(1)  Atypical entrance wounds:

(a)  For a few microseconds after bullet leaves the muzzle, there may be a tail wobble. This produces large atypical entrance wounds at short range.

(b)  The gyroscopic effect of the bullet diminishes as it reaches the end of its flight, wobbles and tumbles and produces large atypical wounds of entrance,

1. Ricochet bullet: A Ricochet bullet is one which before striking the object aimed at, strikes some intervening object first and then after rebounding from there, hits the object. The bullet may ricochet before or after striking the body. It may occur with inferior firearms and low velocity bullets. A large irregularly oval, triangular or cruciate entrance wound with ragged margins is produced. Abrasion collar and burning, blackening and tattooing are absent. Rarely the bullet may hit the body side-on producing an enlongated wound like a key-hole. When the velocity is lost, the bullet only produces an abrasion or contusion. Sometimes after passing though the brain, the bullet may bounce off the inner table of the skull producing a second track.

(d)  The bullet may strike the surface producing a contusion and fall to the ground. This is seen with soft non-jacketed bullets fired from a firearm  with an eroded or worn barrel, and also when the ammunition used is of smaller size than the barrel of the gun.

1. When the bullet hits at an angle, it may graze the surface of the skin leaving a scratch, lacerated furrow (bullet slap or graze) or an incised-looking wound.

(2)  Single Entrance and Multiple Exits: If the bullet splits up within the body and divides into 3 or 4 pieces, there will be several exits. The bullet striking a bone may splinter it and the fragments act as secondary missiles producing several exists.

(3)  Multiple wounds of  Entrance and Exist from a single shot: A bullet may transfix an arm and pass through the chest so that four wounds are produced. A bullet passing through the chest or abdomen and thigh and lower legs produce six wounds. This occurs when the person is running or sitting in an unusual position. In such cases, examination of clothing is very important.

(4)  Entrance wound is present but Bullet is not found in the Body: This occurs when:

(a)  The bullet entering the stomach may be vomited,

(b)  Entering the wind pipe may be coughed up,

1. Entering the gastrointestinal tract may be passed out in the faeces, and

(d)  When it is deflected and passed out by the same wound as it entered.

(5)  Unexplained Bullets in the Body: When a loaded firearm is unused for several years and is fired, the bullet may fail to come out of the muzzle. When it  is fired again the second bullet may go off carrying the lodged bullet with it and both may enter the body through the same wound. This is called a Tandem bullet.

(6)  Fatalities with blank Cartridges: In close discharge a blank cartridge may produce death.

(7)  Firearm going off by itself: The firearm can go off  by itself without any one touching the trigger due to some defect in its mechanism.

AUTOPSY:

(a) Clothing: Remove clothing layer by layer. Avoid cutting or mutilating a wound pattern on clothing. List them all and note their condition and the extent of blood staining. Record the number and position of bullet holes. It is sufficient to describe the number of bullet holes in the outer garment and adding that bullet holes in the remaining clothes correspond in location to the outer garment. The location of bullet holes in clothes, should be described in relation to the distance from collar, seams, pockets, heel level, etc. A single bullet may produce several holes due to the presence of creases in the garment and simulate more than one shot. Air dry clothes if wet. The size of the bullet hole and the extent of soot and powder distribution should be measured and the density of powder stippling noted. Note whether the fibres of the clothing are turned inwards or outwards. Clothing may be forced into the tissues in shot gun wounds.

Number all entrance and exit wounds. The clothes should be preserved carefully in clean brown paper or plastic bags and sent to the laboratory. Photographs of all layers of clothing should be taken with a scale placed nearby. Probes, fingers, etc, should not be introduced through the defects in the clothing as the direction or distribution of fibres will be changed.

(b) Bullet wounds: Do not wash or cleanse the body until samples have been taken for examination for powder residues. Protect the hands with plastic bags.

Shot Gun Wounds:

(a) The exact location of each wound should be noted in relation to its distance from: (i) the top of the head or the sole of the foot. (ii) midline of the body, and (iii) a fixed anatomical landmark.

(b)  The character of the perforation, its shape (stellate, round, slit-like or jagged) and size should be noted and also presence or absence of fouling and stippling.

1. Take photographs of the wounds including a scale.

(d)  Describe the number and distribution of stellite skin perforations caused by individual pellets and the presence  or absence of wad injuries.

1. Measure the total vertical and horizontal spread of the skin wound pattern when satellite perforations are present.
2. Remove as many pellets as possible. X-ray is helpful in locating the pellets.

(g)  Recover wads which reveal the bore of the shot gun and may also have a manufacture’s mark.

 

Rifled Fire-Arm Wounds:

(a)  Note the exact location of each wound.

(b)  The character of the perforation, its shape and size should be noted.

1. Note and measure the abrasion collar, etc. and the powder pattern surrounding the borders of the entrance wound. Difference in the width of the abrasion collar at different points should be noted.

(d)  A scaled photograph or a diagram showing the numbered wounds is useful.

1. If the entrance wound is soiled with blood it should be sponged carefully to know tattooing,

(e)   Track Taken by the Bullet through the body:

1. Bullet tracks should be numbered and described individually. It is advisable to record the wound in the skin and the wound track through the body in one section.
2. Probes should not be introduced through the track.
3. The path taken by the bullet through the body should be carefully traced by dissection. Measure the height of both entrance and exit wounds from the under surface of the heel.
4. Describe all organs and tissues through which the bullet passes and note the size of the defect or lacerations produced; include specific vessels injured and note the quantity and location of internal haemorrhage; note secondary missiles related to fracture of bone.
5. If there are multiple tracks, each should be followed from the point of entrance to exit.

f) Remove the bullet with bare fingers or a forceps protected with rubber tubing may be used.

1. Describe characteristics of the exit wound.

(D) Microscopic Examination: (1) Prepare sections from wounds of entry to demonstrate injury and powder residues. (2) Prepare sections from depth of wound to determine powder residues.

(E) Special Procedures: (1) Photography of wounds. (2) X-ray examination: (a) to locate bullets and shots, (b) to locate fragments of metal and bone, (c) to show course and direction of missiles. (3) Chemical examination: (a) for powder residues. (b) Neutron activation analysis for residues from primer (c) Detection of trace metals.

(F) Specimens to save: (1) The skin around the entrance and exit wounds should be cut out including at least 2.5 cm. of the skin around and 5 mm. beneath the wound and preserved in rectified spirit. (2) Blood for typing. (3) Viscera for chemical analysis.

 

G. PRESERVATION, MARKING AND PACKING OF EXHIBITS:

1. Fire arms: Identifying initials should be scribed on to the gun’s frame, receiver, or slide and on the barrel.
2. Fired cartridge cases: The marks should be scratched on the inside of the open end. They may be wrapped in cotton and packed in cardboard boxes.
3. Fired bullets: The marks should be scratched on the base, wrapped in cotton and packed in cardboard boxes. Each bullet should be packed separately.
4. Pellets, slugs, wads, etc: They may be packed in cardboard box wrapped in cotton after drying and the container labeled.
5. Clothes: The area of the powder tattooing should be preserved by fastening a cellophane paper over it and packed in a box.

 

CIRCUMSTANCES OF DEATH:

(1) Suicide: The sites of election are: (i) temple (ii) centre of forehead, (iii) roof of mouth, (iv) Midline behind the chin, and (v) left side of front of chest. The wound is usually of contact type. A close up or distant shot is rarely suicidal. Suicides usually pull the clothes aside to bare the skin before shooting themselves. The wound is usually single but rarely multiple suicidal wounds are seen involving a single region, e.g. temple, chest or abdomen. In such cases, the first shot does not incapacitate the victim immediately. The weapon is usually found at the hands due to cadaveric spasm. There is usually a motive and he may leave a note. Suicide by firearm is seen mostly in males.

(2) Homicide: A great variety of wounds can occur depending upon the circumstances. A close up or distant shot is usually seen. The wounds may be multiple and may be found on the back or sides of the body, or involve different regions of the body. The weapon will not be found at the scene. There may be evidence of struggle.

(3) Accident: They are rare and usually single. The wounds are found on the front of the body and frequently directed upwards.

 

Precautions:

1. Preserve clothing: a) for correlation with wounds upon the body and (b) to determine entrance and exit wounds.
2. Recover projectiles and fragments of bullets to determine caliber and identity of the weapon.
3. Remember that projectiles may undergo internal ricochet after striking bone, especially in the skull.
4. Remember that projectiles may enter blood vessels or spinal canal and transported to unexpected parts of the body.
5. Caliber of the bullet cannot be predicted by the size of the entrance wound.
6. Do not cause distortion of projectiles by careless dissection.

GUN SHOT WOUNDS

1. Preservation and collection of evidence at the scene of death.
2. Identification of the weapon
3. Discovery of the wounds and identification of gunshot wounds.
4. Number and location of wounds in the clothing and on the body
5. Feature of gunshot wounds and adjacent areas
6. Range of fire
7. Angle of fire
8. Number of shots fire
9. Cause of projectile in the body
10. Retrieval of the bullet or pellets and determination of the type of gun.
11. Retrieval of foreign material (fabric, wadding and so on) from wound tract.
12. Period of survival
13. Identification’s of lethal injury
14. Record of injuries for presentation in court (repu)
15. Special investigation (Finger Print, blood type, toxicology),

EXAMINATION OF THE SCENE

1. Study of the circumstances of shooting
2. Preservation of evidence (Finger Print on the weapon, gunpowder on hands)
3. Examination of the gun and the body, and recording of findings.
4. Collection of evidence (gun empty cartridges, shells, clothing, blood steam hair)
5. Preliminary advice on the live of further investigation.

 

Firearm Injuries

Scene

Besides taking the usual precautions at the scene with regard to the preservation of fingerprints and the position of the body, until the preliminary police examinations have been completed, special caution must be exercised both as regard to handling the weapon or to ensure that it is not touched by anyone. If the missile is found embedded in wood or some similar material, it should not be extracted, but if its examination proves necessary it should be cutout together with material in which it is embedded. Under no circumstances should it be gripped in metal forceps, to avoid any damage before being taken to the laboratory. The same principle applied to cartridge cases found at the scene. Any marks made subsequently upon the missile or cartridge case may make it difficult or impossible for the ballistics experts to match them with particular weapon. If the weapon is at the scene of shooting, its position in relation to the decreased must be noted. It must be borne in mind that even after serious injury, the deceased may be capable of some movement or locomotion before death occurs. The investigating person should keep following points in mind

.

 

Study the circumstances of the firing

• Location of shooting
• Presence or absence of gun
• Type of gun
• Personal history of victim
• Conversation with the witness

Preservation of evidence

• Finger prints on door knobs, weapon, wire glasses tape
• Photographs of scene/video-graphy of scene.
• Pick up weapon from muzzle with gloved hands
• Proper handling of cloth and body
• Type of bullets or shells.

Recording of Findings

• Notes of details of circumstances of death + observation made with photograph.
• General appearance of the location of death.
• If gun into position in relation to the body should be noted as well as its serial number, make model caliber, type of action and adscription of the ammunition.
• Observation on the number of gunshot wounds. Position in the cloths and on body. Notes on positive of boning, tattooing of powder on clothing and wounds of the body.

Collection of evidence

• Gun
• Empty cartridge/bullet, shells, clothing
• Blood stains, hairs

If extended in wall, ceiling or furniture it should be extracted and retained.Bullets put in cardboard boxes, not in metal containers.

The type of bullets and their makings may help identify the gun.

Shells collected in absence of gun- help identify gun.

Preliminary advice on the line of further investigation

• Medical man with wound ballistic training is the best person to interpret wounds on the body

Artifacts in hospital

• Surgical intervention
• Trochar wounds
• Increase in size in decomposed bodies
• Old bullets in body

At the scene, consideration should be given to the presence or absence of weapon, and its position in relation to the body, position of blood stains, signs of disturbance, accessibility to the scene (e.g. how the door was secured from the inside), position of spent cartridge cases, trajectory of missiles, and impact marks on object or surfaces from missiles and their distribution.

The site of the wound in most suicide cases conforms to well recognized selected areas such as temple, mouth, and midline structures to the front of the body. The direction of the wound track from site is a further good indication of the aim of the shooter towards a particular vital structure such as heart or brain,.

The range of discharge of the firearm is another useful factor, which may help confirm on manner of death as being self-inflicted. Unless there is some mechanism to discharge a firearm from a distance further than arm is reach, than such a discharge is extremely unlikely to have been self-inflicted.

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