For years they sat in prison, convicted of heinous crimes they say they didn't commit. Then a scientific test gave credence to their claims of innocence and, almost miraculously, helped set them free.
From Maryland to Kansas, at least nine defendants -- including two who faced the death penalty -- had rape or murder convictions overturned through a technology known as "DNA typing."
Their release from prison not only changed the public persona of these men, it exposed -- in the view of those familiar with these cases -- the fallibility of a system that purports justice for all.
"It's shaking the false confidence that people once had in the certaintyof convictions," said George Castelle, a public defender in West Virginia, where a DNA case helped uncover widespread misconduct by a state police serologist.
Since DNA typing came into forensic use in the late 1980s, it has been used to assess a suspect's culpability in a crime. From bloodstains, seminal fluid, hair follicles, even saliva residue, scientists can extract the genetic material -- deoxyribonucleic acid (DNA) -- that distinguishes one human being from another and compare it to that of suspect and victim.
A test result can point to guilt or innocence; it can affirm a just verdict or uncover a miscarriage of justice.
In Los Angeles, for example, prosecutors are awaiting the results of DNA typing on evidence seized from the home of O. J. Simpson, who is charged with the murders of his former wife and a friend. The tests can determine within a certain probability whether blood samples from the crime scene match Mr. Simpson's or if blood recovered from the former football star's Ford Bronco came from the victims. The test also can exclude someone as a source of evidence.
The releases of the nine convicted felons since 1991 occurred after DNA typing performed on old evidence -- usually semen stains on clothing -- excluded the men as the source.
The cases not only cast serious doubt on someone's guilt, they raised anew questions about the reliability of eyewitnesses and, in two instances, uncovered evidence previously withheld by prosecutors. Despite these successes on behalf of convicted criminals, those familiar with the justice system say that two factors still prevail:
The overwhelming majority of DNA tests in criminal cases helps convict people in America, and the standard forms of evidence -- including witnesses, ballistics and fingerprints -- remain the mainstay of prosecutions.
Prove people innocent
And yet, there is a small but growing caseload of felons seeking to prove their innocence through DNA typing: Defense attorneys are, for example, pursuing two new cases in Virginia and Wisconsin.
"With this technology, we can prove people innocent in a way we could never do before and look at what in the system creates unjust results," says Barry C. Scheck, co-chairman of the DNA Task Force of the National Association of Criminal Defense Lawyers. "DNA can kind of give you an incredible window, and it indicates how fragile our system is."
But do the post-conviction DNA cases reflect, as Mr. Scheck suggests, a system ill-equipped to identify and analyze its mistakes and the reasons for them? Or are they anomalies in a system that metes out justice fairly in spite of the crush of daily business?
Mr. Scheck, a professor at Benjamin N. Cardozo Law School in New York who has been at the forefront of re-examining old cases with DNA technology, believes that the system doesn't "seriously examine the issue of factual innocence."
'Our error rate'
"People can be convicted if they are factually innocent," said Mr. Scheck, who oversees the Innocence Project, a program at the law school aimed at using DNA testing to identify inmates who may have been wrongly convicted.
"What we have to do is examine scientifically our error rate. If we did, I think there are several other things we would do differently."
Prosecutors and forensic scientists, however, argue that the post-conviction cases coming through the courts in recent years cannot be used to indict an entire system. Since its introduction in criminal cases, DNA typing has also helped to prevent wrongful arrests.
"The technology has increased our investigative arsenal to help us make sure that the person who is being charged and convicted is the right person," said William T. Ferris, a Long Island, N.Y., prosecutor whose office has seen two convicted defendants released because of DNA evidence.
"They [the defense] get a win and they say the whole system is corrupt. They forget the thousands of other cases that come through and it's the right person."
Since the FBI opened its DNA forensic laboratory in December 1988, the bureau has conducted about 2,500 tests a year. About one-third of the DNA typings have excluded the person as a suspect in a case, according to an FBI spokesman.