[templar]

...scientists can conclude that if the lead content of bullet A matches bullet B, and bullet B's content matches bullet C, then it is safe to testify that bullet A and bullet C are a match even if their test results don't match identically.

If A=B and B=C but A<>C then there is something seriously (scientifically) wrong with the definintion of 'matches'.

[Comus]

Wait a minute. I thought bullets came out of guns with serial numbers that matched the guns. This has to be a lie. Why else do they collect fired bullets from guns?

[You Gotta Be Kidding Me]

"If A=B and B=C but A<>C then there is something seriously (scientifically) wrong with the definintion of 'matches'."

For fingerprints, you need twelve points where print A precisely overlays print B, before you can say in a court of law that the prints "match". Even now, however, fingerprint "matching" is comming under fire. Also 2 in 10,000 people have "the same" (scientifically) fingerprints.

Bullet rifling marks are a whole 'nutha matter. This puts a real damper on the "balistic fingerprint" database crap, doesn't it.

[El Gato]

If A=B and B=C but A<>C then there is something seriously (scientifically) wrong with the definintion of 'matches'.

It's more like A~=B and B~=C -> A~~=C. I sure wouldn't want to be convicted of a crime because I happened to stop by the sporting goods store, gun shop, or gun show table, right after or before the real killer. I can't believe anyone was ever convicted on such flimsy evidence. But I guess many have been. Those lead batches are each used in tens of thousands (or more) of bullets, and it stands to reason that a shipment of a particular caliber, to any one dealer will probably contain bullets all, or almost all, made from the same batch. How does that prove anything?