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Detective Techniques
This Season's Highlights
Next on History Detectives.

WATCH SEASON 7 HIGHLIGHTS .

(Dur: 4.31)

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FEATURE - expert'S OPINION

CLICK ON the numbers to see what the marks on a bullet can tell investigators about the bullet and the gun that fired it.

Clue CLASS CHARACTERISTICS

Proof: the kind of gun that fired the bullet

Inspecting the measurable features of a bullet will tell an expert the one specific type of gun, a Colt .45 for example, that could have fired the bullet. But any gun of the identical type would produce identical marks.

Clue INDIVIDUAL CHARACTERISTICS

Proof: the one gun that fired the bullet

By studying the fine lines (striations) on the sides of a bullet, essential evidence can be found. These random, irregular marks are caused by tiny defects in the interior of a gun barrel. No two barrels make identical marks.

Clue MATCHING MARKS

Proof: this gun fired this bullet

A bullet is damaged on impact. Compared side-by-side with an undamaged 'test' bullet fired by the same gun, some differences are inevitable. Some bullets are too distorted to allow any proof to be found.

Clue BALLISTIC FINGERPRINTS

Proof: this bullet came from a known gun

A new ballistics program has been proposed: a national database, containing a digital record of the unique 'ballistic fingerprints' of every gun sold. Instant ballistics proof - without the actual weapon.