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FBI's Forensic Test Full of Holes
Ernest Roger Peele, a retired FBI agent who testified about bullet matching in 130 cases, stands by his testimony but said that sometimes the nuances of science get "lost in the adversarial nature of the courtroom." He said he would no longer tell jurors that bullets can be linked to specific boxes because of the science academy's findings.
Peele, who said he was frustrated that he was never contacted by the academy, added that his bullet matches were meant to be "a part of a puzzle" and never the only forensic evidence. "Is it possible there are innocent people in jail? Yes. Is it possible that bullet lead was part of that process? Yes."
The Origins of the Science
The FBI's bullet-lead analysis was created more than four decades ago to link suspects to crimes in cases in which bullets had fragmented to the point where traditional firearms tracing -- based on gun-barrel groove markings -- would not work.
So FBI scientists used chemistry to try to find matches. Their assumption was that bullets made from the same batch of lead would have the same chemical composition. U.S. bullet-makers recycle lead from car batteries and melt it down in huge amounts, and it was believed that each batch would produce bullets sharing the same trace elements.
The FBI first used the technique after Kennedy's assassination, hoping to determine whether various bullet fragments came from the same gun. In July 1964, then-FBI Director J. Edgar Hoover wrote to the commission investigating the assassination that the bureau's findings were "not considered sufficient" to make any matches.
By the early 1980s, the bureau was the only practitioner of the science and routinely used it to help state and local police link crime-scene bullets to those in a gun or a box owned by a suspect. There are few federal murder statutes, but the FBI routinely helps local law enforcement by providing forensic expertise in homicide cases.
In the mid-1990s, Lundy used the science to help prove that Clinton White House lawyer Vincent W. Foster committed suicide, internal FBI documents show.
In the early days, bullet fragments were subjected to neutron beams that would allow scientists to measure the presence and amounts of at least three chemical elements: antimony, arsenic and copper. If two bullets had similar measurements of those three elements -- the FBI allowed for a small margin of error -- they were declared a match.
In 1996, the bureau switched to a new method called "inductively coupled plasma optical emission spectroscopy," in which scientists identified and measured seven trace elements in the bullets, adding the elements bismuth, cadmium, tin and silver. The goal was to increase the precision of the tests. But at the same time that it was measuring more elements, the FBI doubled the margin of error for declaring matches.
"Not enough suspects were being caught in the new net using seven elements, so they chose to use a bigger net," said Clifford Spiegelman, a statistician at Texas A&M University who reviewed the FBI's statistical methods for the science academy.
The bureau conducted a study in 1991 that called bullet-lead analysis a "useful forensic tool" that produced "accurate" and "reproducible" matches.