Handguns and rifles fire ammunition or cartridges composed of a primer, gunpowder or propellant, and a bullet or projectile. When a firing pin of a weapon strikes the primer, the resulting explosion ignites the gunpowder. Gunpowder, vaporized primer, and metal from a gun may be deposited on skin and/or clothing of the victim. In addition, elements from the primer may be deposited on objects in close proximity to a discharged weapon.
Gunpowder comes out of the muzzle in two forms:
1. Completely burned gunpowder, called "soot" or "fouling", can be washed off the skin.
2. Particles of burning and unburned powder can become embedded in the skin or bounce off and abrade the skin. The marks on the skin are called "tattooing" or "stippling".
The presence or absence of gunpowder on the clothing or skin indicates whether the gunshot was contact (loose or tight), close, intermediate, or distant.
Tight contact — All gunpowder residue is on the edges or in the depths of a wound. There may be searing or burning of wound margins or reddening of surrounding skin due to carbon monoxide gas produced by burning powder. There is often tearing of the skin around the entrance wound in head wounds because of pressure buildup and blow-back of the skin towards the muzzle.
Loose contact — Gunpowder may escape from the barrel and be deposited around the edges of a wound.
Close range — Close range gunshot wounds occur at muzzle-to-target distances of approximately 6 to 12 inches. Both fouling and stippling are present.
Intermediate range — These wounds occur at muzzle-to- target distances of approximately 12 inches to 3 feet. There is no fouling, only stippling or deposition of particles on clothing.
Distant wounds — No fouling or stippling.
Entrance and exit wounds are generally easy to differentiate. Entrance wounds tend to be circular defects with a thin rim of abrasion caused by a bullet scraping and perforating the skin. Entrance wounds of the face can be quite atypical appearing because the surfaces are not flat.
Exit wounds may be circular like entrance wounds, but they are often irregular in shape. They may be slitlike or have ragged edges. They do not have a rim of abrasion-like entrance wounds unless a victim's skin is pressed against another object. This is called a "shored" exit wound. Skin around an exit wound may also be discolored because of underlying bleeding in the soft tissues.
The scene must be examined for bullets and cartridges. Bullets may be caught in clothing after exiting the body.
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