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"The study specifically urges the bureau's chemists to stop a practice known as "data chaining" that chemists have used in the past to match bullets to a crime."

All the "urging" in the world won't stop it. It will take a prominent case where the evidence is thrown out, before the practice will stop.

Take notice of this report, all you "law & order at any cost" advocates.

1 posted on 11/21/2003 1:38:38 PM PST by You Gotta Be Kidding Me
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To: You Gotta Be Kidding Me
...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'.

2 posted on 11/21/2003 1:54:08 PM PST by templar
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To: You Gotta Be Kidding Me
good thing they proved Oswald acting alone killed kennedy...back in the old days when labs and tests were more accurate huh!
3 posted on 11/21/2003 1:55:46 PM PST by joesnuffy (Moderate Islam Is For Dilettantes)
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To: *bang_list
BANG!


6 posted on 11/21/2003 2:10:12 PM PST by Travis McGee (----- www.EnemiesForeignAndDomestic.com -----)
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To: Thud
You are going to have some real fun with this one.
7 posted on 11/21/2003 3:32:10 PM PST by Dark Wing
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To: You Gotta Be Kidding Me
This is a matter of tolerance stacking, something that always must be avoided in science and engineering.

Say you are matching to an accuracy of 0.0000001

Sample 'A' is 0.1234567
Sample 'B' is 0.1234568

They match within the margin of error.

Sample 'B' is 0.1234568
Sample 'C' is 0.1234569

They match within the margin of error

By the FBI standards

Sample 'A' = 0.1234567
and
Sample 'C' = 0.1234569
Difference = 0.0000002
are a 'match' by data chaining even though they differ by twice the margin of error.

With a longer chain, you can make any two samples match.
In other words, it is pure pseudoscience.
They are making it up as they go along.

So9

8 posted on 11/21/2003 3:33:19 PM PST by Servant of the 9 (Real Texicans; we're grizzled, we're grumpy and we're armed)
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To: You Gotta Be Kidding Me
Thanks for posting this article.
11 posted on 11/21/2003 5:28:16 PM PST by neverdem (Say a prayer for New York both for it's lefty statism and the probability the city will be hit again)
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To: You Gotta Be Kidding Me
I remember a case about 30 years ago when a person in Mobile, Alabama was convicted of killing someone with a sawed off shotgun.

The key evidence was ballistics.

Now obviously the question is, what markings are left by a shotgun barrel. The answer is that the barrel was sawn off roughly and it is said to have left marks on the buck shot which matched the rough edges from the cut.

I thought at the time that I didn't believe it and I still don't.

13 posted on 11/21/2003 5:44:04 PM PST by yarddog
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