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
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"
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) bullet fingerprinting
: When the gun fires, the casing is forced backward against the breech face, transferring its texture to the metal.
: The pin strikes the primer at the back of the casing, leaving a unique indentation. Barrel Evolution Unlike human fingerprints
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 hooks and pins that pull the spent casing out and toss it away leave distinct scratches on the rim. The Technology of Tracking Despite its usefulness
To manage these vast amounts of data, law enforcement uses specialized databases and imaging systems.