Firearm Injuries

Here’s information on firearms and their injuries:

Definition of Firearms

• A firearm is any weapon that discharges a projectile by using gunpowder.
• It is a weapon designed to cause injuries through the use of gunpowder.
• Firearms consist of a metal barrel, which is a long, hollow steel cylinder.

Classification of Firearms

Firearms are classified based on the condition of their barrel:

I. Rifled Weapons

• The bore has shallow, spiral “grooves” called rifling, with projecting ridges called “lands”.
• Rifling imparts a spinning motion to the bullet, increasing penetration, ensuring a straight course, and preventing unsteady movement.
• Types:
  • Rifles (air- and gas-operated, 0.22, military and sporting).
  • Single-shot target-practice pistols.
  • Revolvers.
  • Automatic pistols.
  • True automatic weapons (machine guns).
  • Assault Rifles.
  • Air Rifle and Air Pistol.
  • Zip Gun and Stud Guns.
  • Improvised or Country-made Firearms.

II. Smooth-Bored Weapons (Shotguns)

• The interior of the barrel is smooth.
• Intended for firing a single ball, slug, or charge of shots.
• Common gauges are 12, 16, and 20.

Peculiar Effects of Firearm Injuries

• Bullet Velocity: The ability of a bullet to wound is directly related to its kinetic energy. High-velocity bullets cause disproportionately greater tissue damage.
• Tissue Density: Greater tissue density results in more energy discharged by the bullet. For example, a bullet may cause slight damage to soft tissues but extensive comminution of bone.
• Hydrostatic Forces: These cause excessive destruction, especially when a bullet passes through fluid-distended hollow organs like the stomach or bladder, leading to extensive lacerations.
• Wobble/Yaw/Tumble: A bullet traveling irregularly (sideways or backwards) instead of nose-on produces an irregular lacerated wound and greater tissue crush.
• Temporary Cavitation: When a high-velocity bullet moves through the body, it transfers kinetic energy, causing surrounding tissue to be thrown radially, forming a temporary cavity.

Rifled Firearm Injuries (including distance of firing)

Wounds from rifled weapons are classified by distance from the muzzle to the victim:

• Contact Shot
  • Firm Contact: Wound similar to shotgun. Muzzle impression (patterned abrasion) may be seen.
  • Effects: Large and irregular wound. Causes cavitation and laceration due to expanding gases. Margins are hyperaemic, contused, and everted. Singeing of hair may occur. Wound of entry and track may appear pink due to CO.
  • Skull: Markedly large and irregular wound due to gas expansion between scalp and skull. Soot may deposit on bone and inner skull. Fissured fractures radiate from defect.
• Close Shot (up to 8 cm)
  • Effects: Circular wound with inverted edges. Skin surrounding wound is burnt, blackened, and tattooed. Hair is singed. Blackening is wiped off, but tattooing is not. Abraded and grease collar are present. Wound track may be pink due to CO.
• Near Shot (up to 50 cm)
  • Effects: Round hole, slightly smaller than bullet diameter, with bruised and inverted margin. Zone of blackening and tattooing present. No singeing of hair or skin. Abrasion and grease collar are present.
  • Distant from Flame/Smoke Range: Lacerating and burning effects of gases usually lost due to dispersion cooling. Individual tattoos are caused by unburnt powder grains.
• Distant Shot (Above 50 cm)
  • Effects: Circular wound, smaller than missile, with inverted margins. No burning, blackening, or tattooing seen. Two zones: inner grease collar, outer abraded collar. Palms and soles may show irregular, stellate appearance without abrasion ring.

Assessing the Range of a Rifled Firearm Injury

• Powder Residue: The presence or absence of smoke, flame, tattooing, etc., on or in the body helps determine range.
• Intensity/Spread: As distance increases, intensity of blackening and tattooing decreases, while spread increases.
• Test Firing: Test firing with the suspect weapon and same ammunition at varying distances helps estimate range by matching pellet markings and other findings.
• Lead Deposits: Lead deposits around the entry wound can estimate range.
• Tissue Reaction: Swelling and homogenization of dermal collagen due to bullet heat are more marked at entrance than exit sites.
• X-ray Examination: In decomposed or burned bodies, X-rays can help determine the range of fire.

Rifle Cartridge

• Consists of a metal cylinder with a flat base, usually with a rim.
• A primer cup (percussion cap) is fitted in the center of the base.
• Gunpowder lies between the detonator and the bullet.
• Many bullets have a circumferential groove (cannelure) near the base.

Shotgun Injuries

Wounds from shotguns are classified by distance from the weapon:

• Contact and Near Contact Wounds
  • Effects: Single, usually round, equal to bore in size, often ragged due to shot and gases. Severe disruption of subcutaneous and deeper tissues.
  • Tight Contact: Muzzle impression (copy or recoil abrasion) may be seen. Soiling and burning are within the wound.
  • Skull: Less disruption than with rifled weapons; bursting open of the skull is not seen.
• Close Range (within a few inches to 90 cm)
  • Effects: Skin around wound is singed by flame, blackened by smoke, and tattooed by powder grains. Tattooing is not wiped off. Hair is singed.
  • 60-90 cm: Single circular aperture (2.5-4 cm diameter) with irregular edges. No burning or blackening, but some tattooing.
  • Plastic Wad: May produce a circular entrance wound with a Maltese Cross pattern of abrasion.
• Short to Medium Range (1 to 4 metres)
  • 1-2 metres: Single circular aperture (4-5 cm diameter) with irregular and lacerated edges. No burning, blackening, or tattooing. Wads may be found deep inside.
  • 2-4 metres: Shot mass begins to spread; individual pellet holes may be detected. Wound of entry is irregular.
• Long or Distant Range (above 4 metres)
  • Effects: Shots spread widely and enter as individual pellets, producing separate openings. Area of spread can be 10-15 cm in diameter.
  • Skull: Energy of shots greatly reduced; pellets usually do not travel entire brain substance.

Shotgun Cartridge

• Consists of a short metal cylinder continuous with a cardboard or plastic cylinder.
• Has a rimmed base with a detonator cap (percussion cap) in the center.
• Contains gunpowder, a thick felt-wad with cardboard discs, and shot (pellets).
• A retaining cardboard disc and pressed cylinder walls hold components in place.
• Wad diameter is greater than the bore of the gun, acting as a piston to seal the bore.
• Some cartridges contain a ‘power piston’ (plastic cup with four leaflets).

Entry Vs Exit Wound

Trait	Entrance Wound	Exit Wound
Size	Smaller than bullet diameter	Bigger than bullet, or same size for high velocity
Edges	Inverted	Everted, puckered, or torn
Abrasion Collar	Present	Absent
Grease/Dirt Collar	Present	Absent
Burning/Blackening/Tattooing	May be seen around the wound	Absent
Bleeding	Less	More
Fat Protrusion	No protrusion, except in contact shot	May protrude
Tissues (Color)	May be cherry-red due to CO	No color change
Clothing Fibers	Turned in and carried into wound	Turned out
Lead Ring	May be seen by radiological examination	Absent
Skull (Inner Table)	Punched-in hole, cone-shaped piece detached	Punched-out opening
Skull (Outer Table)	Cone-shaped piece detached, bevelling	Bevelled opening

• Shored Exit Wound: If skin at exit is firmly supported (e.g., by belt, wall), wound appears circular with abrasion margin, resembling an entrance wound.

Choking of Firearms

• Choking refers to the narrowing of the distal 7 to 10 cm of a shotgun barrel.
• Different degrees exist: full-choke, half-choke, quarter-choke, or improved cylinder.
• Choking lessens the rate of spread of shot after it leaves the muzzle, increasing explosive force and velocity.