When a gun is fired, several mechanical actions leave distinct impressions on the ammunition. These marks are primarily categorized into two types: 1. Striation Marks (on the bullet)
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"
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 bullet fingerprinting
As a bullet travels through a gun barrel, it is gripped by —spiral grooves machined into the metal to make the projectile spin for stability.
The shell casing is also marked by various parts of the firearm's internal mechanism: When a gun is fired, several mechanical actions
: The National Integrated Ballistic Information Network is a federal database used to share digital images of ballistic evidence.
: When the gun fires, the casing is forced backward against the breech face, transferring its texture to the metal. Every shot fired slightly alters the microscopic striations
: The Integrated Ballistic Identification System (IBIS) is the hardware and software used to capture these high-resolution 3D images.