Firearm and Bomb Blast Injuries

Firearm Injuries and Bomb Blast Injuries

These notes cover firearm injuries, specifically gunshot wounds from rifled firearms and injuries from smooth bore firearms (shotguns), as well as wound ballistics.

Wound Ballistics (Firearm Wounds)

Doctors performing autopsies on firearm cases need to consider several factors related to wound ballistics:

1. Type of Weapon: Is it a rifled or smooth bore firearm?

2. Nature of Projectile: What kind of bullet or pellets were used?

3. Nature of Propellant: What type of gunpowder was used?

4. Direction of Firing: From what direction was the shot fired?

5. Range of Firing: What was the distance between the firearm and the victim?

Injuries Caused by Rifled Firearms (Gunshot Wounds)

• Wounds produced by rifled firearms are called gunshot wounds.

• Entry Wound: The penetrating wound caused by the bullet entering the body.

• Exit Wound: The wound caused by the bullet leaving the body after entry.

• Track of Injury: The path traveled by the bullet between the entry and exit wounds.

• Range of Firing: The distance between the muzzle of the firearm and the target.

Features of Gunshot Wounds

When a rifled firearm is fired, several components emerge from the muzzle and affect the target:

• Projectile (Bullet): Causes entry and exit wounds and abrasion or contusion collar.

• Gun Smoke and Soot: Cause smudging or blackening around the entry wound.

• Gunpowder Particles: Cause tattooing (peppering or stippling) on the skin.

• Gases: Cause blast effects and cherry red discoloration of tissues due to carbon monoxide combining with hemoglobin to form carboxyhemoglobin.

• Flame: Causes scorching or singeing of the skin and hair.

• Metal Particles: Leave a metal ring around the entry wound.

• Grease or Dirt: Create a grease collar around the entry wound.

Entry Wound Characteristics

• The bullet stretches the skin before penetration, causing the margins to invert.

• Abrasion Collar: Friction from the spinning bullet creates an abrasion collar (typically about 0.3 cm).

  • In some cases, a contusion collar may form instead of an abrasion.

• Grease or Dirt Collar: Lubricant or dirt from the barrel is deposited around the entry wound.

  • When both abrasion and grease collars are present, the grease collar is in the inner zone, and the abrasion collar is in the outer zone.

Other Effects

• Flame: Can cause burning (scorching) of the skin and singeing of hairs. Clothes may show burning or melting.

• Unburnt Gunpowder: Causes tattooing on the skin, appearing as small, discrete, black specks.

• Smoke: Causes blackening or smudging due to superficial deposition of smoke particles.

• Carbon Monoxide: Causes cherry red discoloration around the wound due to carboxyhemoglobin formation.

• Metal Particles: May leave a lead ring or metal ring around the entry wound, detectable by X-ray or neutron activation analysis.

• Gases: In contact range firing, gases can cause a blast effect, tearing the skin, everting wound edges, and extruding fat.

Entry Wound in Rifled Firearm

• If only one wound present, the bullet may still be in the body, exited/dropped from the entry wound, or (rarely) been coughed out/lost in vomit or feces.

• The appearance of the entry wound depends on:

  1. Type and caliber of weapon.

  2. Type of bullet.

  3. Type of gunpowder.

  4. Striking velocity of bullet.

  5. Site of the body hit.

  6. Range of firing.

Range of Firing

1. Contact Shot: Muzzle is in contact with the body.

2. Close Shot: Victim is within the range of the flame.

3. Near Shot: Victim is within the range of gunpowder deposition but outside the range of flame.

4. Distant Shot: Victim is beyond the range of flame, smoke, and gunpowder residue.

Contact Shot

• Also known as a point-blank shot.

• The entry wound is large, shows cavitation, and may be triangular, stellate, cruciate, or star-shaped due to the explosive effect of gases.

• Skin around the entry wound may show an imprint abrasion of the muzzle end of the gun.

• Burning, soiling by smoke, and tattooing are minimal or absent on the adjacent skin, but the track is blackened with gunpowder residue and may show charring.

• Inner tissues may be cherry red due to carbon monoxide.

• On the head, blackening may be observed in the pericranium area around the entry wound.

• Skull fractures show a clean, punched-in hole in the outer table at the entrance wound, while the inner table shows a beveled crater.

• Margins of the entry wound may be everted with protrusion of fat.

• Back Spatter: Blood, hair, tissue fragments, and cloth fibers may be sucked into the barrel.

Close Shot

• Flames travel about $7.5$ cm in a revolver or pistol and $15$ cm in a shoulder rifle.

• Entry wound appears circular when the bullet strikes at a right angle and oval if at an acute angle. Gunpowder residues are distributed circumferentially or on one side, respectively.

• Skin shows scorching, singeing, and blackening.

• Abrasion, grease, or dirt collar may be present.

Near Shot

• Victim is within the range of powder deposition but outside the range of flame (within $60$ cm).

• Singeing and scorching are absent.

• Abrasion and grease collars are present.

• Blackening occurs up to $30$ cm and is absent beyond.

• Tattooing is present.

• Edges of the entry wound are inverted.

Distant Shot

• Victim is beyond the range of gunpowder.

• Entry wound is circular with inverted margins.

• Scorching, singeing, blackening, and tattooing are absent.

• Grease and abrasion collars may be present.

Exit Wound

• May be absent if the bullet is lodged in the body, lost in vomit/cough/feces, or exits through the same entry wound.

• Multiple exit wounds may occur if the bullet breaks apart or a bone fragment exits along with the bullet.

• Exit wounds vary in size and shape.

• Edges of the exit wound may be everted, puckered, or torn.

• Blackening, tattooing, singeing, abrasion collar, and grease collar are absent.

Importance of Exit Wound

• Helps determine the direction of firing.

• Helps ascertain the victim's posture at the time of firing.

• Indicates the number of bullets in the body.

Unusual Effects of Rifled Firearm

• Atypical large entry wound.

• Bullet graze: Bullet licks the skin, producing a sliding abrasion or laceration.

• Single entry wound with multiple exit wounds.

• Ricochet bullet: Deflected from its path by striking an object before hitting the body.

• Multiple entry and exit wounds with one bullet.

• Tumbling of bullet: Bullet rotates end-on-end during motion.

• Yawning of bullet: Bullet travels in an irregular fashion instead of nose-on.

• Kennedy phenomenon: Artefact produced by surgical intervention that distorts the wound.

Smooth Bore Firearm Injury (Shotgun Injuries)

Features

When a shotgun is fired, the following components exit the muzzle:

1. Pellets

2. Wad

3. Cardboards

4. Gunpowder

5. Smoke

6. Flame

7. Gases

Characteristics of Shotguns

• Multiple pellets are used.

• Dispersion of pellets occurs as distance increases.

Range of Components

• Flame: $30$ cm

• Smoke: $50$ cm

• Gunpowder: $100$ cm

• Cardboard: $2$ meters

• Wad: $2-5$ meters

• Pellets: Compact mass up to $45$ cm, then disperse

Entry Wound

Ranges:

1. Contact range

2. Close range

3. Short range

4. Medium range

5. Distance range

Contact Shot

• Muzzle is held firmly against the skin.

• The wound is single.

• Burning or blackening is minimal or absent.

• Muzzle impression may be present.

• Cherry red color may be present.

• Shape is usually circular, but over bone, it may be stellate or ragged due to gas accumulation under the skin.