Gunshot wounds

This article deals with gunshot wounds, which are seen by (forensic) pathologists in the context of forensic autopsies.

An introduction to forensic pathology is in the forensic pathology article.

Accounting

Number of entrance wound should equal the number of exit wounds -- if it doesn't there are:

• Bullets in the body,
• "Tandem bullets" -- two bullets entered at the same place,
• Secondary projectile -- the bullet hit something, e.g. bone, and made it fly out of the body,
• You missed an entrance or exit,
  • Places to look:
    • Below chin (common in suicides),
    • In mouth (common in suicides),
    • Back,
    • ... anywhere the sun don't shine.

Firearm projectiles

Evidence

• Bullets are often good evidence:
  • The calibre (size) and markings from the barrel (on handgun/rifle projectiles) allow it to be match to the weapon that fired it.
  • Thus, all projectiles are recovered from a body... and it is routinue to X-ray all gunshot victims.

Classification

Two broad groups:

• Shotgun projectiles.
  • Many small pellets.
    • Birdshot - smaller.
    • Buckshot - larger.
• Handgun/rifle projectiles.
  • Similar in size to the barrel - large when compared to shotgun projectiles.
  • Bullets from handguns/rifles are marked by the barrel on the way-out (by grooves which in part spin on it to improve accuracy).

Subclassification

• Rifled projectile are often group by diameter, e.g. ".22 caliber" (~5.6 mm).

Entrance wounds

Characteristics:

• Circular/round defect --especially if the projectile strikes at a right angle to the surface.
  • If the projectile strikes at an angle the injury will be elliptical and the long axis of the ellipse will lie approximately in the plane the bullet traveled.
• An abrasion, or scraping, --concentric or eccentric-- usually surrounds a deep wound (key feature -- used to differentiate from exit wounds).
  • Eccentric abrasion suggest directionality.
• Usually smaller than exit wounds.
  • In skull the inner table defect is typically larger than outer table defect ("internal bevel").

Atypical entrance wounds:

• Irregular (non-circular/non-elliptical) margin.
  • May be due to close range/contact.
    • Classically results in a "stellate" pattern.
  • Bullet ricochets --hits other object before hitting target, gun defective -- bullet's long axis doesn't coincide with its velocity vector.
    • Classically results in a "D-shaped" wound.

Exit wounds

Characteristics:

• Usually bigger than entrance wounds.
• Morphologic shape -- variable.
  • Round, stellate, ovoid.
• NO abrasion at wound margin (key feature).
• In skull -- outer table defect typically larger than inner table defect (external beveling).

Atypical exit wounds:

• "Shored" exit wounds.
  • Exit defect created whilst surface supported/adjacent to firm surface.
  • Supporting surface may lead to abrasion.
  • May appear to be an entrance wound.

Special entrance/exit wounds

• Keyed wounds.
  • Combination entrance/exit wounds -- result from a bullet grazing the victim.

Distance of shooter

Contact

• Muzzle impression.
• Stellate splitting/tearing of the skin -- especially if it overlies a bony surface.
• Soot/gun powder residue - deep in the wound.

Close range

• Stippling (tattooing) - punctate abrasions around the entrance wound.
  • Suggests a distance > 1 cm and <= 60 cm (rim fire cartridge), > 1 cm and <= 90-120 cm (centrefire cartridge).
• Soot/gun powder residue - dirt at the entrance, can be wiped-off.

Distant

• No soot.
• No stippling.

Notes:

• Absence of soot & stippling does not exclude near range -- may be assoc. with clothing or intermediate target separated from the victim post-injury.

Injury severity due to GSWs

The damage of a projectile depends on:

• Where the bullet strike, e.g. ascending aorta vs. brain vs. tibia vs. gluteus maximus.
• Kinetic energy of the bullet.
  • Ek=1/2*m*v^2.
    • Velocity is more important -- as it is squared (duh).
• Cavitation effect; temporary cavity formation.

See also

• Forensic pathology.