Gunshot wounds

Depiction of a gunshot wound of the brain. (WC/National Library of Medicine)

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 wounds should equal the number of exit wounds.

If the above is not so... the explanation is:

1. Bullets are still in the body.
2. "Tandem bullets" -- two bullets entered (or exited) at the same place.
3. Secondary projectile -- a bullet hit something, e.g. bone, and made it fly out of the body.
4. Pathologist missed an entrance or exit.
   • Places to look:
     • Below chin (common in suicides).
     • In the mouth (common in suicides).
     • Ears.
     • Back.

"Sites of election" (suicide)

Common places where people shoot themselves:

• Mouth.
• Temple.
• Left chest.
• Below the chin.

Firearm projectiles

Evidence

• Bullets are often good evidence:
  • The calibre (size) and markings from the barrel (on handgun/rifle projectiles) allow it to be matched 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.
  • Buckshot - usu. 7-9 pellets, typically 6-9 mm (diameter).
  • Birdshot - many pellets, typically 2-5 mm (diameter).
  • Slug - one large bullet; may be confused with a (high power) rifle projectile.

• 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" is 0.22 inches (~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").

• 

  GSW patterns. (WC)

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/irregular.
  • May be : stellate, ovoid, round.
  • Looks like it may be easily approximated with sutures -- unlike a typical entrance wound.
• NO abrasion at wound margin - key feature.
• In skull -- outer table defect typically larger than inner table defect (external beveling).

• 

  Exit wound. (WC)

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.
• Attached skin tags can give directionality; they are classically found at the aspect of the wound distant from the projectile's origin.
  • The University of Utah describes it as:

Characteristically, the side of the [skin] tag demonstrating a laceration is the side of the projection toward the weapon.

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.
• Scalloped border/edge in shotgun wound.

Intermediate

• Stippling.
• No soot.

Shotgun:

• "Satellite" wounds.
• Wad marks - typically have sharp edges +/- sharp corners.

Indeterminate/Distant

Previously known as distant for non-shotguns, as this is the pattern seen if a shooter is far from the victim.

• No soot.
• No stippling.

Notes:

• Absence of soot & stippling does not exclude near range; the lack of soot and stippling may be explained by clothing or an intermediate target that the projectile travelled through prior to striking the victim.
• Intermediate should not be confused with indeterminate.

Summary tables

Summary table - hand gun entry wounds:

Distance	Skin splitting	Soot	Stippling	Other
Contact	+/- (only if to head)	+ (in wound)	+ (in wound)	muzzle imprint
Near contact	-	+ (in & around wound)	+	no muzzle imprint
Intermediate	-	-	+	should not be confused with intermediate target
Indeterminate	-	-	-	previous known as distant

Summary table - shot gun entry wounds:

Distance	Skin splitting	Soot	Stippling	Projectile topography	Wad mark
Contact	+/- (only if to head)	+ (in wound)	+ (in wound)	round	-
Near contact	-	+ (in & around wound	+ (in & around wound)	round with scalloped border	-
Intermediate	-	-	+	round with scalloped border + "satellite" bullets	+/-
Distant	-	-	-	scattered, multiple round-same size	-

Injury severity due to GSWs

The damage of a projectile depends on:

• Where the bullet strikes, e.g. ascending aorta vs. brain vs. tibia vs. gluteus maximus.
• Kinetic energy of the bullet.
  • $E_{k}={\frac {1}{2}}mv^{2}$
    • Velocity is more important -- as it is squared (duh).
• Cavitation effect; temporary cavity formation.

See also

• Forensic pathology.