When a bullet strikes the body, a common question arises: are exit wounds consistently larger than entry wounds? The answer is not straightforward, as the size and appearance of both entry and exit wounds depend on a complex interplay of physical forces and biological reactions. Understanding these dynamics requires a look into how a bullet transfers its energy to human tissue.
How a Bullet Creates a Wound
A bullet creates a wound by transferring its kinetic energy to the tissues it encounters. As the projectile moves through the body, it crushes and shreds tissue directly in its path, creating the permanent cavity. This permanent cavity represents the actual hole left by the bullet’s passage.
Beyond this path, energy dissipates in a shock wave, pushing surrounding tissue outward. This forms a temporary cavity, larger than the bullet’s diameter. The temporary cavity exists briefly, typically 5 to 10 milliseconds, before tissues recoil, leaving the permanent wound track. A bullet’s journey begins at an entry point and may conclude with an exit point if enough energy remains to pass through.
Factors Determining Wound Size
The size of a bullet wound, especially the exit wound, is influenced by how kinetic energy transfers and dissipates within the body. As a bullet travels through tissue, it loses energy, absorbed by surrounding structures, causing damage. This energy transfer determines wound severity.
Bullet characteristics, such as design and stability, significantly impact the extent of tissue disruption. Expanding bullets, like hollow points, deform upon impact, increasing their frontal surface area and transferring more energy to the tissue. This deformation can lead to a larger wound channel upon exit.
If a bullet tumbles or yaws (deviates from its straight path) within the body, it presents a larger cross-sectional area, increasing damage and potentially creating a wider exit wound. Fragmentation, where a bullet breaks into multiple pieces inside the body, also increases wound size. Each fragment creates its own path, leading to multiple wound tracks and wider areas of damage upon exit.
Different tissue types react distinctly to a bullet’s passage; dense, inelastic tissues like bone absorb more energy and can fragment, creating secondary projectiles that further enlarge the wound. The temporary cavity, often at its maximum size just before exit, contributes to overall tissue damage and a larger exit wound.
Why Exit Wounds Vary
While exit wounds are often larger and more irregular than entry wounds, this is not a universal rule. The exact appearance and size of both entry and exit wounds are highly variable, underscoring the complex nature of ballistic trauma. Several scenarios exist where an exit wound might be smaller than the entry wound or even absent.
Low-velocity projectiles or those encountering minimal tissue may create smaller exit wounds, or the bullet might lodge within the body. If a bullet has expended most of its kinetic energy, it may lack sufficient force to create a large exit defect. The elasticity and density of traversed tissues also play a role; some tissues might stretch and recoil more effectively, minimizing visible damage at the exit point. The outcome of any gunshot wound is influenced by a multitude of factors, making each injury unique.