How are firearms classified — rifled vs smoothbore?
Firearms fall into two basic groups: rifled firearms (revolvers, pistols, rifles) and smoothbore firearms (shotguns). A third group, country-made firearms, uses unusual projectiles and is seen more often in less developed countries. The examiner's job is to work out entry and exit, distance and direction of fire, and whether the wound was inflicted in life.
| Feature | Rifled firearm | Smoothbore (shotgun) |
|---|---|---|
| Barrel | Spiral grooves (rifling) inside the barrel | Smooth inner surface |
| Projectile | Single bullet, spun by the rifling for stability | Cartridge of many tightly packed pellets held by plastic or cardboard wads |
| Marks on projectile | Rifling marks — class characteristics that help identify the weapon type | Pellets carry no rifling marks |
| Wound pattern | Single entry wound per bullet | One large wound up close; multiple pellet wounds at distance |
| Penetration | High | Each pellet penetrates less; damage is spread over a wider area |
How does a bullet damage tissue — what is temporary cavitation?
A bullet crushes the tissue directly in its path, the permanent track. High-energy bullets also throw tissue outwards, forming a short-lived temporary cavity. The radial acceleration, shearing, stretching and compression damage tissue well away from the track.
- Temporary cavitation is more extensive in solid, incompressible organs; solid organs are more susceptible to serious injury than hollow organs or elastic tissue.
- Large arms may also send a sonic pressure wave; it rarely matters except in hollow viscera like the intestine, which can rupture.
- Clothing or intervening objects slow the projectile and can stop soot and powder from reaching the skin — so missing residue does not prove a distant shot.
How do entry and exit wounds differ?
| Feature | Entry wound | Exit wound |
|---|---|---|
| Size and shape | Smaller, regular, usually round (unless over bone) | Larger and irregular, especially when bone is broken |
| Margins | Inverted — tissue pushed into the wound | Everted — outward bevelling of skin and soft tissue |
| Abrasion collar | Present — rim of abraded skin around the hole | Absent, except when skin is pressed against a hard surface (shored exit) |
| Grease collar / bullet wipe | Present — lubricant and dirt wiped off the bullet | Absent |
| Burns, soot, tattooing | Present depending on range | Never — these come from the muzzle side |
| Foreign material | Not a distinguishing feature | Bone fragments, clothing fibres or organ tissue are often carried out |
A purplish ecchymotic (contusion) ring from torn dermal vessels may surround the entry hole. For other wound types — abrasions, bruises and lacerations — see mechanical injuries.
How is the range of fire estimated from the wound?
When a gun fires, the bullet leaves the muzzle together with flame, hot gases, smoke (soot), unburnt and partly burnt powder grains, metal scrapings and grease. Each travels a different distance, so what is deposited on the skin tells you roughly how far away the muzzle was.
| Range | Key finding | Other features |
|---|---|---|
| Contact (firm or loose) | Muzzle imprint on the skin | Firm contact: soot and burns inside the track, not on the surface. Loose contact: some soot escapes onto the surrounding skin. Over bone: stellate (star-shaped) wound |
| Near-contact / close range | Flame burns and singeing of hair | Flame reaches about 15 cm from small arms and 30 cm from large arms; soot and tattooing also present |
| Intermediate (mid) range | Tattooing (stippling), no burns or singeing | Powder grains reach the skin; soot is scanty or absent; unburnt particles travel about 30–60 cm from small arms |
| Distant range | No burns, soot or tattooing | Only the abrasion collar and grease collar from the bullet itself |
| Indeterminate | Irregular wound beyond the weapon's usual range | Caused by yawing — the bullet tumbling off its axis |
- Contact wound over bone (skull): gas from the barrel strikes bone, reflects and balloons the scalp, tearing it into a stellate wound; blood and tissue can back-spatter onto the weapon and the shooter's hand.
- Firm contact over soft tissue: burns and soot are found in the depth of the wound with a clear muzzle pattern around it.
- These distances are approximate — every weapon must be test-fired with the same ammunition to estimate range reliably.
How do shotgun wounds change with distance?
A shotgun releases the whole load — many pellets plus the wads — rather than a single projectile. The pellets travel together at first and then spread out, so the wound pattern is the best guide to range. Shotguns propel flame about 15 cm, smoke and gas about 30 cm and unburnt particles about 60 cm.
| Distance | Wound appearance |
|---|---|
| Contact | Like a rifled contact wound; a double-barrel gun pressed on the skin may leave a double muzzle imprint |
| Within 30 cm | Single circular wound with smooth or crenated margins, no satellite pellet holes, wads in the track; burns, singeing, soot and tattooing present |
| Beyond 60 cm | Pellets begin to disperse: nibbled 'rat-hole' circular wound with few satellite holes; no burns or singeing; little or no redness from carbon monoxide; wads may be present |
| Beyond 1 m | Central rat-hole wound with multiple satellite pellet holes; no burns, soot, tattooing or wads |
| Beyond 10 m | Pellets fully dispersed: many small punctate wounds and no central hole |
What do gunshot wounds of the skull show — bevelling and Puppe's rule?
- Entry in the skull shows internal (inward) bevelling — the hole is wider on the inner surface.
- Exit in the skull shows external (outward) bevelling — wider on the outer surface. Telling entry-type from exit-type bevelling is crucial for the direction and angle of the shot.
- Keyhole lesion: a tangential shot produces one defect with a round entry part (inward bevelling) and an elongated exit part (outward bevelling).
- Puppe's rule: a fracture from a later impact stops at a pre-existing fracture line. Fractures from an exit wound stop at the fractures around the entry wound, which helps sequence multiple shots or blows.
For skull fractures and intracranial bleeding from blunt trauma see head injury.
How is a firearm death examined — what must be preserved?
The wound examination answers the medicolegal questions: entry and exit, distance and angle of the shot, type of firearm, whether the wound was inflicted in life, and the probable manner of death — homicide, suicide or accident. Findings can corroborate or contradict eyewitness accounts, so evidence must be protected from the scene onwards.
- Handle the body as little as possible to preserve gunshot residue and blood spatter.
- Put paper bags, not plastic, over the hands — plastic causes condensation that can spoil the evidence.
- Transfer the body in a body bag or clean linen; do not strip it before the pathologist sees it, because clothing holds damage patterns and residue that indicate range.
- At least an X-ray is done in every firearm death so that every bullet and fragment is found and recovered at autopsy; postmortem CT maps the track, entry and exit and organ damage.
- Recovered bullets are examined for rifling marks to link them to a weapon.
How is gunshot residue detected?
Gunshot residue (GSR) comes mainly from the primer, plus burnt and unburnt powder and particles from the cartridge case and projectile. Residue on skin and clothing is used to reconstruct shooting incidents and to estimate the firing distance.
| Element | Source compound |
|---|---|
| Lead | Lead azide or lead styphnate |
| Antimony | Antimony trisulphide |
| Barium | Barium nitrate |