In a decision Monday overturning a 1997 murder conviction, the court said Michael S. Behn deserves a new trial because expert testimony based on the FBI technique was central to his conviction.
"The integrity of the criminal justice system is ill-served by allowing a conviction based on evidence of this quality, whether described as false, unproven or unreliable, to stand," the judges said.
The ruling is believed to be the first to overturn a conviction based on a challenge to the FBI analysis of the lead content of bullets since the National Academy of Sciences last year raised new questions about the technique.
FBI Lab Director Dwight Adams asked for the academy study in 2003 after a retired bureau metallurgist began questioning the validity of the science that matches bullets by comparing the chemical composition of their lead content. The academy, chartered by Congress and privately run, is widely respected.
The FBI request came as the Associated Press reported the retired metallurgist's findings based on his own research into the science behind the lead bullet analysis. The AP also disclosed that an FBI scientist had admitted giving false testimony about lead bullet analysis in a Kentucky case.
Adams has estimated that the technique has been used in about 2,500 cases since 1980 and has been mentioned in court testimony about 500 times since then.
Barry Scheck, president of the National Association of Defense Lawyers, said the ruling will probably be followed by similar challenges in other courts.
"There's no question since the National Academy of Science report that testimony pursuant to CBLA (chemical bullet lead analysis) is unreliable," said Scheck, who is a founder of The Innocence Project, a legal team at Benjamin Cardozo Law School at Yeshiva University in New York which uses DNA evidence to clear wrongly convicted individuals.
The bullet analysis technique in question, says Sheck, can't be used "for any probative evidentiary purpose. In many of these cases, people been wrongly convicted."
One of the nation's most prominent defense lawyers, Scheck's past clients include and .
In the New Jersey case that sparked Monday's court ruling, William Tobin, the retired FBI metallurgist who first questioned the technique, submitted a sworn statement that resulted in a new trial for Behn, who was sentenced to life in prison after his 1997 conviction in the shooting death of a coin dealer.
The FBI is the only law enforcement agency that analyzes the metal content of bullets. It is done when bullet fragments are too small or damaged to compare the marks left on the slug by the barrel of the firearm. The goal is to determine if the bullet from the crime matches other bullets found in the suspect's possession or weapon.
In a technique known as chaining, researchers compare the amounts of trace elements in a series of bullets. If they find that bullet A is like bullet B and B is like C and C is like D and so on, they then conclude that A is the same as E because they are part of the same chain.
In the New Jersey case, the appellate court said the FBI analysis that used chaining to link bullets found at Behn's residence with those used in the killing was the only expert testimony in the circumstantial case that was not countered by the Behn's lawyers during his trial.
"We conclude that the expert testimony was based on erroneous scientific foundations," the court said.
Behn's lawyer had asked the appeals court to order a new hearing on the evidence challenging the FBI analysis. But the court went a step further, reversing his conviction and ordering a new trial.