The shell casing is also marked by various parts of the firearm's internal mechanism:
: When the gun fires, the casing is forced backward against the breech face, transferring its texture to the metal. bullet fingerprinting
: The National Integrated Ballistic Information Network is a federal database used to share digital images of ballistic evidence. The shell casing is also marked by various
Despite its usefulness, "bullet fingerprinting" is not always a definitive proof of guilt. Several factors can complicate or even invalidate a match. 1. Barrel Evolution Several factors can complicate or even invalidate a match
: The Integrated Ballistic Identification System (IBIS) is the hardware and software used to capture these high-resolution 3D images.
Unlike human fingerprints, a gun's "fingerprint" changes over time. Every shot fired slightly alters the microscopic striations in the barrel. Experts may only fire a limited number of test rounds because the fifth shot might already look different from the first. 2. Success Rates and "Expensive Failures"