Bullet Identification

[wickeddog]

Does anyone know of any articles, studies, books, or reports discussing the likelihood of recovering a bullet that can be used for a forensic ballistics match? I am investigating a case where 25 bullets were fired and the ballistics lab report states that none of the bullets recovered can be matched to any of the seven guns recovered.

[Buzzcook]

http://www.fbi.gov/hq/lab/fsc/backis...m#Introduction

Google knows all tells all

[Bud Helms]

Microscopic view of imperfections in the rifling of a barrel




Rifling on a fired bullet

These pics from that link, with their captions, are misleading. I always chuckle at it on TV too. All those little parallel marks at 90 degrees to the rifling don't print on the bullet. The bullet is dragged across those marks as the bullet passes down the barrel. The "signature" left on the bullet is nothing resembling the pattern seen in that photo. It's a signature all right, but it has waaay less detail than that to match against a barrel.

Those breechface (boltface) marks on the head of the case is a lot more of what you would think of as a direct "print".

Good link, Buzzcook.

[wickeddog]

I have looked at a lot of information about forensic ballistics, how it was invented, how the computer database system is fantastic/terrible, how the lands and grooves are etched onto the bullet as it rifles down the barrel, and so on, but I have not seen any statistics about how often a bullet can be matched to a gun.

I have also noticed that most of the information on the internet is from ballistics professionals who have a vested interest in promoting the idea that ballistics forensics is useful and works great. I have not been able to find one study that looked at the actual usefulness of the process in contrast to the conditions of the bullets that are dug out of bodies, walls, cars...

I just cannot find out whether there are millions of bullets with perfect identification marks just waiting to be matched up with a gun, or whether 99% of bullets recovered are so deformed that they could not be matched even when the gun is known?

[NWPilgrim]

Interesting question. You could further refine it to what percentage is "scientifically" able to be used for an ID to a specific firearm, and what percentage is usable to influence a jury?

I suspect a good portion of the "identification" performed is not to a specific firearm, but to narrow the possibilities down to an already suspected firearm: caliber, brand (e.g., distinctive Glock firing pin), rifling pattern (# lands/grooves, twist rate).

My sister was trying to convince me that at a local trial a "firearms expert" testified that a recovered bullet could tell whether the firearm was fired accidentally or on purpose?!?! Whether true or not, the "ballistic evidence" is used to influence a jury to somebody's benefit and another's detriment.