A New Jersey appeals court overturned a 1997 murder conviction yesterday, ruling an FBI crime lab technique that prosecutors relied on to link the fatal bullets to the defendant was based on "erroneous scientific foundations."
The decision 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 the FBI has used for decades to match bullets to crimes.
FBI Lab Director Dwight E. Adams asked for the academy study in 2003 after retired bureau metallurgist William A. Tobin questioned the validity of the science that matches bullets by comparing the chemical composition of their lead content. 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.
Tobin's sworn statement in the New Jersey case resulted in a new trial for Michael S. 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 whether 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 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.
The appellate court said the FBI analysis that used chaining to link bullets found at Behn's residence "was based on erroneous scientific foundations."
