Tuesday, February 04, 2003

The F.B.I.'s chemical analysis of bullets used in crimes has come into question. I am no scientist & certainly am not in the ammunition making business, but even I see something wrong with the idea that bullets are produced in lots of under 10,000. I know people who cast their own lead bullets who melt 10 to 20 pounds of lead at a time, so the idea that a professional bullet maker would only use 70 lbs of lead at a time is a little far fetched. I suspect they have only gotten away with it because loading your own ammunition is nowhere near as commonplace as it was, & to the average person on a jury 70 lbs. or 10,000 bullets seem like a lot.
One thing that i found disappointing about the article was that it didn't mention the flaws with the F.B.I's other form of bullet analysis:what has been recently called ballistic fingerprinting. Without getting into too much detail a firearms rifling undergoes changes every time an object passes through, thereby changing the marks left on a bullet. Low powered rounds take longer than higher powered rounds, & the material used to make a bullet has it's effects, but basically after so many rounds pass through a rifled barrel the pattern cannot 100% be matched to a previous bullet fired from the same gun. In fact passing a steel brush or even steel wool down the barrel a few times will change enough of the riflings features to preclude an exact match. The only way to get a conclusive match is to compare bullets fired shortly after each other - & the bullets must have the same material construction, velocity, etc... to produce a 100% match. The more shots fired in between means the less likely a match will be. But the F.B.I's reputation quells a lot of doubts & much what the Bureau claims is taken for granted as fact. Luckily I grew up in a very skeptical part of the country. In fact back home the F.B.I. & BATF & most other government law enforcement agencies are still referred to as 'revenuers'.
I am not certain if the article doesn't deal with the credibility questions of ballistic fingerprinting because of ignorance or because they assume it's unquestionable, but with all the calls for legislation in this area it would be a good topic of media attention. That is if the media weren't in favor of gun control generally.
In any event it seems like a lot of cases could be up for review & quite a few sentences reversed if word of this gets out.
For more on ballistic fingerprinting & it's shortcomings look here, here & here

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