Bullet: Fingerprinting

: The pin strikes the primer at the back of the casing, leaving a unique indentation.

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" bullet fingerprinting

To manage these vast amounts of data, law enforcement uses specialized databases and imaging systems. : The pin strikes the primer at the