Myth: Every firearm leaves a unique “fingerprint” that can pinpoint the firearm used

Fact: A group of National Research Council scientists concluded that this has not yet been fully demonstrated. Their research suggests that current technology for collecting and comparing images may not reliably distinguish very fine differences.¹

Fact: “Firearms that generate markings on cartridge casings can change with use and can also be readily altered by the users. They are not permanently defined like fingerprints or DNA.”²

Fact: “Automated computer matching systems do not provide conclusive results.”³

Fact: “Because bullets are severely damaged on impact, they can only be examined manually”.⁴

Fact: “Not all firearms generate markings on cartridge casings that can be identified back to the firearm.”⁵

Fact: The same gun will produce different markings on bullets and casings, and different guns can produce similar markings.⁶ Additionally, the type of ammunition actually used in a crime could differ from the type used when the gun was originally test-fired — a difference that could lead to significant error in suggesting possible matches.⁷

Fact: The rifle used in the Martin Luther King assassination was test fired 18 times under court supervision, and the results showed that no two bullets were marked alike.⁸ “Every test bullet was different because it was going over plating created by the previous bullet.”

Fact: “The common layman seems to believe that two bullets fired from the same weapon are identical, down to the very last striation placed on them by the weapon. The trained firearms examiner knows how far that is from reality.”⁹

This is an excerpt from “Gun Facts” by Guy Smith, available free from http://www.gunfacts.info