A gunshot wound (GSW) is a form of penetrating trauma caused by the transfer of kinetic energy from a fired projectile, typically a bullet, to the body’s tissues. The ultimate appearance of the wound depends on various factors, including the projectile’s speed and design, the range of fire, and the elasticity and density of the tissues it encounters. Understanding the full scope of this injury requires examining the visible points of entry and exit, as well as the unseen damage within.
The Appearance of the Entrance Site
The visual characteristics of the skin at the point of entry vary based on the distance between the muzzle of the firearm and the target. A distant-range wound, where only the bullet strikes the skin, presents as a clean, circular or oval defect. This hole is usually surrounded by a reddish-brown ring known as an abrasion collar. This marginal abrasion is a distinct feature of an entrance wound, formed by the friction of the projectile scraping the outer layer of skin upon entry.
Near-contact or intermediate-range wounds introduce additional visual elements from the combustion products of the gunpowder. Hot, unburned powder particles and metallic fragments ejected from the muzzle impact and embed in the skin, creating a pattern of small, punctate abrasions called stippling or tattooing. This stippling cannot be wiped away and indicates that the shot was fired from a relatively close distance, generally less than three feet.
In a contact wound, where the muzzle is pressed directly against the skin, the appearance is further modified by the explosive force of the expanding gases. The hot gases and soot are injected directly beneath the skin, causing a characteristic blackening, or fouling, of the wound edges. If the contact occurs over bone, the gases are reflected back, causing the skin to tear outward in an irregular, star-shaped pattern known as a stellate wound. This type of wound may also show a distinct muzzle imprint on the skin.
Internal Tissue Damage and Cavitation
Once the projectile breaches the skin, the primary damage inside the body is defined by two distinct cavities. The first is the permanent cavity, which is the actual track of crushed and destroyed tissue left directly in the bullet’s path. The size of this cavity is determined by the caliber and deformation of the bullet as it travels.
The second, and often more extensive, damage is caused by the temporary cavity, which is a massive expansion of tissue away from the bullet track due to the kinetic energy transfer. This pressure wave radially stretches and compresses the surrounding tissue in milliseconds. The temporary cavity can be many times larger than the projectile itself, causing internal tearing, bruising, and cell death in areas the bullet never physically touched.
The extent of internal damage depends on the type of tissue involved. Organs with low tensile strength and elasticity, such as the liver, spleen, and brain, are easily damaged and appear pulped or lacerated far beyond the permanent cavity. More elastic tissues, like muscle, can stretch and recoil, minimizing the overall destruction, though contusion and internal bleeding are present along the temporary cavity’s path. The energy transfer often results in fragments of the projectile or bone being carried forward, creating secondary paths of destruction.
The Appearance of the Exit Site
The exit wound marks the final point where the projectile, or its fragments, leaves the body, and its appearance is generally different from the entrance site. Exit wounds are typically larger and more irregular in shape compared to the neat entry hole. This irregularity occurs because the bullet has often yawed, tumbled, or fragmented inside the body, presenting a larger, deformed surface area upon departure.
The edges of an exit wound are often everted, or pushed outward. Unlike the entrance wound, a true exit wound lacks the signs of gunpowder residue, soot, or stippling on the skin, as these components travel only a short distance from the muzzle. The skin surrounding the exit hole is torn and lacerated, and the edges can often be reapproximated, which is not usually the case with an entrance wound where tissue is destroyed.
Atypical exit wounds can occur if the skin is pressed against a firm object, such as a wall or a tight belt, at the moment of exit. This pressure can cause the skin edges to be scraped, producing a pattern referred to as a “shored” exit wound. This scraping can create a surrounding abrasion that may visually mimic the abrasion collar of an entrance wound. The presence or absence of an exit wound depends on whether the projectile has transferred all its kinetic energy before traversing the body.
Ammunition and Velocity Factors
The final presentation of a bullet wound is modified by the characteristics of the projectile and its speed. Projectiles are classified by their velocity: rifle bullets are typically high-velocity (over 2,000 feet per second), and handgun bullets are lower-velocity. High-velocity rounds increase the size of the temporary cavity, resulting in greater internal tissue destruction.
The physical design of the bullet also influences the injury profile. Full metal jacket (FMJ) rounds are designed to resist deformation and are more likely to pass through tissue without fragmenting, resulting in a narrower permanent cavity. Conversely, expanding projectiles, such as hollow-point or soft-point bullets, are designed to deform or “mushroom” upon impact.
This expansion increases the bullet’s cross-sectional area, causing it to transfer its energy more rapidly within the tissue. The result is a larger permanent cavity internally and a greater likelihood of a large, ragged exit wound due to energy transfer and potential fragmentation. The combination of high velocity and an expanding projectile creates the most devastating wounds, characterized by extensive internal maceration and large, irregular surface defects.