Gun forensic science - what can the really tell from cases, bullets, etc?

[dogngun]

I watched a" Law and Order" re-run recently. One of the Detectives glanced at a few fired cases about 8 feet away and said, "Huh - 9mm Glock."
I wondered what actual forensic labs can tell from fired cases, bullets, etc, in the real world. I know about the lands and grooves, firing pin indentations, extractor marks, etc, but mainly these things seem to be useful in relating a particular gun to a particular fired cartridge - that is, if you don't have the gun, you don't really have too much.

I find a lot of what I think are really ridiculous things on TV shows, and I'd like to know what is real and what isn't, if anyone can shed some light on this.

Thanks.

(FWIW, Law and Order also had one BG shooting a "25mm" auto pistol.)

mark

[rwilson452]

First off, anything you see on TV or in the movies doesn't have any relationship to reality. Writers and directors are not going to let facts get in the way of telling a good story. Glocks do have a rather distinct striker mark and leave a bulge on the case that is notable. It requires close examination to see this not across the room. Striations on the bullet can be traced to a particular barrel. marks in the primer can be traced to but is more difficult. tracking metallurgy either for the case or bullet has been discredited. reading the head stamp is meaningless as they are produced by the 1,000,000s same goes for powder, too large a uniform batch. If you mold your own bullets that metallurgy could be traced back to you as each batch of lead you make will be unique. Your molds may leave identifying marks the sprue cutter is unique after some use.