Skip to comments.Science Casts Doubt on FBI's Bullet Evidence
Posted on 02/02/2003 10:59:34 PM PST by Kay Soze
Method uses trace elements in lead to link slugs from crimes with suspects' ammunition. Study finds it is based on false assumptions. By Charles Piller and Robin Mejia Special to the Times
February 3 2003
The body of coin dealer Robert Rose was discovered in his Main Street office in South River, N.J., on a steamy July evening in 1995. He had been shot four times in the head.
There were no witnesses, no fingerprints, no gun.
But a chemical analysis of bullets by the FBI seemed to conclusively link the rounds that killed Rose to a box of cartridges belonging to one of his customers, Michael Behn. Lead in the different bullets bore the same telltale pattern of impurities, an FBI expert told the jury. Behn was convicted of the murder.
The same technique has been used in thousands of criminal cases over the last 30 years. Testimony by FBI experts about chemical "matches" between bullets has helped put hundreds of defendants behind bars across the country. In one Texas case, such testimony contributed to the conviction of an accused murderer, who was put to death.
Now, emerging scientific evidence has called the technique into question.
A Times examination of technical studies and trial transcripts and interviews with former FBI technicians, independent scientists and legal scholars suggests that the bureau's use of evidence derived from the lead in bullets may be based on faulty assumptions that greatly overstate the importance of matches.
(Excerpt) Read more at latimes.com ...
a. The chemical composition does not form a unique chemical signiture, becaus on cooling and solidifying, impuriites freeze out very non-uniformly - a fact that any semi-competent metalurgist would know. "Bullets created from the same block of lead can appear unrelated and bullets produced years apart can appear virtually identical."
b. "FBI examiners have testified that bullets are often smelted from batches of lead as small as 70 pounds enough to make about 10,000 .22-caliber bullets.But according to the study, ammunition is usually created from lots of lead that weigh 50 tons or more and yield up to 17 million .22-caliber bullets a number that would dramatically dilute the significance of any match."
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