Temporary Cavity
Definition
The transient radial tissue displacement produced by a bullet's passing. Caused by the transfer of kinetic energy to surrounding tissue via compression and shear. Significant at rifle velocities above approximately 750 m/s (Sellier-Kneubuehl threshold); largely irrelevant at typical handgun velocities.
- Collapse time
- Within milliseconds
- Rifle velocity threshold
- Approximately 750 m/s
- Mechanism
- Kinetic energy transfer via compression and shear
- Visibility at autopsy
- Not directly visible; inferred from hemorrhage and tissue damage
Common questions
What is a temporary cavity in a bullet wound?+
A temporary cavity is the radial stretching of tissue that occurs as a bullet passes through the body. The kinetic energy of the bullet pushes tissue away from the wound track in all directions, creating a cavity that expands and then collapses back within milliseconds. It is driven by the energy transfer from the projectile.
Can you see a temporary cavity at autopsy?+
No. The temporary cavity collapses within milliseconds and leaves no persistent open space. However, it does cause permanent tissue damage at its margins, tearing vessels and fascia. Pathologists infer that significant cavitation occurred by looking at hemorrhage distribution and other tissue damage around the wound track, and by correlating the damage pattern with expected projectile velocity.
How big can a temporary cavity get?+
At high velocity, a temporary cavity can reach 5 to 10 times the diameter of the bullet itself. The size depends heavily on projectile velocity. Rifle wounds at velocities above roughly 750 meters per second produce significant cavitation. Handgun wounds, which travel much slower, create much smaller temporary cavities.
Related terms
- Permanent Cavity
- The lasting wound channel produced by the bullet's direct crushing and laceration of tissue. Diameter approximates expanded projectile diameter. At handgun velocities,...
- Abrasion Collar
- The rim of abraded, dried skin surrounding a gunshot entry wound, produced by the bullet stretching the skin inward before perforation. Width...
- Accidental Discharge
- Unintended firing of a weapon without a deliberate trigger pull, usually caused by mechanical defect, sear wear, drop impact or unsafe handling.
- Ballistic Coefficient (BC)
- The ratio of a projectile's sectional density to its drag relative to a reference standard (G1 or G7). Higher BC means less...
- Blow-Out Exit Wound
- A large, ragged exit wound with radiating lacerations produced when the bullet retains high residual kinetic energy at exit and the skin...
- Choke (Shotgun)
- Constriction at the muzzle of a shotgun barrel that controls pellet spread. From most-open to most-tight: cylinder, improved cylinder, modified, full choke.
- Deflagration
- A subsonic combustion front propagating through an explosive by thermal conduction. Characteristic of low explosives such as black powder and smokeless powder;...
- External Ballistics
- Study of bullet flight from muzzle to target. Governed by gravity, air drag, wind, spin-stabilisation, Magnus effect and (at long range) Coriolis...
- FBI 10% Gelatin Protocol
- The standard medium for law-enforcement ammunition testing, adopted after the 1986 Miami shootout. Ten percent by weight porcine gelatin calibrated with a...
- Grease Ring
- A grey-to-black discolouration at the outer margin of the entry wound's abrasion collar, caused by lubricant and metal fouling on the bullet...
- Hydrostatic Shock
- The contested hypothesis that a high-velocity bullet generates a remote pressure wave through body fluids sufficient to produce immediate neurological incapacitation without...
- Internal Ballistics
- Study of what happens inside the firearm from primer ignition to bullet exit at the muzzle. Includes propellant combustion, gas pressure, bullet...
Explained in these topics
- Internal, External and Terminal Ballistics: BasicsRadial stretching of tissue away from the wound track by the pressure wave. Collapses within milliseconds. Diameter can reach 5 to 10 times bullet diameter at...
- Penetration Mechanics and the Hydrostatic-Shock ModelThe transient radial tissue displacement produced by a bullet's passing. Caused by the transfer of kinetic energy to surrounding tissue via compression and she...
- Velocity, Penetration, Dispersion, Ricochet and Accidental DischargeRadial stretch cavity that pulses open and collapses behind the bullet. Driven by kinetic energy transfer. Bigger in high-velocity rifle wounds, smaller in han...
- Wound Ballistics: Entry Wounds, Exit Wounds and CavitationThe transient radial tissue displacement produced by energy transfer from a high-velocity projectile. Collapses within milliseconds but tears vessels and fasci...