Report: FBI tests on bullets flawed

By Charles Piller
Los Angeles Times

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The method, which measures the likelihood of a chemical match between bullets found at crime scenes and those in the possession of a defendant, has been used for more than three decades. The Los Angeles Times obtained a draft summary of the report, which is expected to be released by the National Research Council (NRC) in December.

"In the future, it would be very difficult for prosecutors to get that kind of evidence admitted," said William Thompson, a professor of law and criminology at the University of California, Irvine.

He called the report "a slap in the face of the FBI."

An FBI spokesperson said the agency would not comment until the report was final. The National Research Council also would not comment, but a source close to the study indicated its primary conclusions would stand.

The chemical analysis of bullets found at crime scenes involves analyzing the material for traces of contaminants or additives, such as tin and antimony. The precise amount of contaminants is compared to the results from bullets found in a suspect's possession.

FBI examiners have often stated or implied in court that a bullet can be traced to a specific manufacturing batch — even to a particular box.

The technique has offered a way to solve crimes involving gun violence when no gun was found. It has strengthened weak cases in which evidence is scarce or circumstantial.

The NRC panel substantially agreed with recent research indicating that bullets from the same source of lead can significantly vary in their chemical makeup, and bullets from different sources — even those manufactured years apart — can share nearly identical amounts of trace elements.

The finding contradicted some prosecutors' depictions of each batch of lead as being unique, like a snowflake or fingerprint. The study suggests the number of "matching" bullets was impossible to determine and could be in the tens of millions or higher — reducing the significance of a match.

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