Science Casts Doubt on FBI's Bullet Evidence

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.

The FBI likens its lead technique to fingerprint analysis. Bullets found at crime scenes are tested for minute amounts of arsenic, tin, silver and other contaminants or additives. Those findings are compared with results of similar analysis of bullets found in the possession of suspects. FBI examiners have claimed in court to be able to link one bullet to others from the same production run -- even from the same box.

The technique has proved especially important in cases in which prosecutors have little or no direct evidence, such as fingerprints or an eyewitness identification.

There is no dispute that trace elements of chemicals can be precisely measured in bullets. The controversy centers on how the FBI interprets the data.

For years, FBI laboratory examiners operated on the assumption that each batch of bullet lead was unique. So if the same trace elements were found in the same concentrations in two bullets, the reasoning went, those bullets must have been made at the same time and in the same place.

Premises Questioned