This segment was originally broadcast on Nov. 18, 2007. It was updated on Sept. 12, 2008.
Aside from eyewitness testimony, some of the most believable evidence presented in criminal cases in the United States comes from the FBI crime laboratory in Quantico, Va. Part of its job is to test and analyze everything from ballistics to DNA for state and local prosecutors around the country, introducing scientific credibility to often murky cases.
But a six-month investigation by 60 Minutes and The Washington Post last November showed that there are hundreds of defendants imprisoned around the country who were convicted with the help of a now discredited forensic tool, and that the FBI never notified them, their lawyers, or the courts, that the their cases may have been affected by faulty testimony.
The science, called bullet lead analysis, was used by the FBI for 40 years in thousands of cases, and some of the people it helped put in jail may be innocent.
As correspondent Steve Kroft reports, one of them is Lee Wayne Hunt, who is now serving a life sentence for murder in North Carolina.
Lee Wayne Hunt tells Kroft he's been behind bars for over 22 years and 6 months, and maintains he's an innocent man. "What I've said from the word get go that I ain't -- never killed nobody. I didn't have nothing to do with this," he says.
Hunt was convicted in 1986 of murdering two people in Fayetteville, N.C., based on the testimony of two questionable witnesses and what turned out to be erroneous ballistics testimony from the FBI lab.
For years, the FBI believed that lead in bullets had unique chemical signatures, and that by breaking them down and analyzing them, it was possible to match bullets, not only to a single batch of ammunition coming out of a factory, but to a single box of bullets. And that is what the FBI did in the case of Lee Wayne Hunt, tying a bullet fragment found where the murders took place to a box of bullets the prosecutors linked to Hunt.
"I put it exactly the way it sounded to me, and the way that I believe it to be," Hunt says. "He said that this box of bullets is the same box of bullets that was used to kill these people, made on, about the same time."
"I think everybody in the courtroom assumed that this was valid evidence," says Hunt's attorney, Richard Rosen.
Asked how important he thinks this was to his client's conviction, Rosen says, "I thought it was very important to our client's conviction. It was the single piece of physical evidence corroborating their story. And it came from, you know, it came from the mountaintop."
The FBI first used bullet lead analysis while investigating the assassination of John F. Kennedy, trying to match pieces of bullets discovered at Dealey Plaza with bullets found in Lee Harvey Oswald's rifle.
By the 1980's, the FBI was routinely using this analysis to link bullet fragments found at a crime scene with bullets found in the possession of a suspect, almost always in cases where more reliable ballistics tests were impossible.
"And could you run like a standard ballistics test on this?" Kroft asks William Tobin, a former chief metallurgist for the FBI.
"No," Tobin says. "They're too deformed for the conventional ballistics examinations."
Tobin says the Quantico lab was the only place in the country that did bullet lead analysis, and the assertion that you could actually match a bullet fragment to a specific batch or box of bullets went unchallenged for 40 years -- until Tobin retired in 1998 and decided to do his own study, discovering that the basic premise had never actually been scientifically tested.
"FBI lab personnel testified that you could match these fragments to this bullet," Kroft remarks.
"Yes, that's correct," Tobin says.
Asked what he found out, Tobin tells Kroft, "It hadn't been based on science at all, but rather had been based on subjective belief for over four decades."
"So what you're saying is that this is junk science?" Kroft asks.
"That's correct," Tobin says. "It's worthless as a forensic tool."