"The Case for Innocence" explores this question, profiling four compelling cases where DNA evidence has been ignored, discounted, or kept secret.

One case is that of prisoner Clyde Charles. For eighteen years he proclaimed his innocence in a Louisiana rape case. But for nearly a decade, state and federal officials blocked his appeals for a DNA test. The efforts of lawyer Barry Scheck and the Innocence Project, coupled with FRONTLINE's media attention, finally pressured authorities to allow the test. It came back negative, and in December 1999 Charles was freed.

"It was surprising to me to learn that prisoners--some on death row--have great difficulty convincing the state to release new evidence which can prove their innocence," says FRONTLINE producer Ofra Bikel. "But I was stunned to find that in cases where DNA tests are conducted, and the results clearly support claims of innocence, the tests are often ignored, and these individuals remain imprisoned."

Barry Scheck and the Innocence Project have successfully exonerated more than thirty-five prisoners using DNA testing. But, DNA exclusion does not necessarily lead to freedom. The case of Roy Criner is an example.

Arrested in 1985 and charged with the rape and murder of a sixteen-year-old Texas girl, Criner was convicted and sentenced to 99 years. In 1996, he submitted to a DNA test based on advances in DNA testing. The tests came back negative, proving it was not Criner's DNA. Dissatisfied by the results, the state decided to do its own test, which also came back negative.

To nearly everyone's surprise, however, the District Attorney dismissed the tests and opposed a new trial. (see video excerpt about this decision.) And the Texas Court of Criminal Appeals supported him. Justice Sharon Keller wrote for the majority, arguing that just because the recovered DNA belonged to someone other than Criner, it did not demonstrate his innocence. She reasoned that the negative result was of little consequence. "It just doesn't mean that he didn't have sex with her."

Innocence Project co-founder Peter Neufeld says this is not a new theory. "In almost all our cases, the prosecution's theory of the case was that one person seized the woman, raped her, and then left her. Once we get the DNA exclusion, a whole range of new prosecution theories emerge."

Neufeld is one of several defense attorneys, prosecutors, and judges interviewed about why not everyone in the legal system wants to examine cases of innocent people wrongfully convicted and why the system resists conceding errors and correcting mistakes.

This FRONTLINE report also highlights how safeguards once available to protect people like Roy Criner are now few and far between. In recent years, a conservative Supreme Court and a Congress eager to seem tough on crime have been radically reducing the avenues by which the wrongly convicted might be freed. As a result, the last hope for many such prisoners is a governor's executive pardon. Yet the idea of governor as safety net is a dangerous proposition, as FRONTLINE discovered in the case of Earl Washington.

L. Douglas Wilder, Governor of Virginia between 1990 and 1994, could have pardoned death-row inmate Washington, who had been convicted of a rape and murder. After ordering a DNA test, which excluded Washington as the contributor of the biological evidence, Wilder's office kept the results secret and commuted Washington's sentence to life in prison rather than granting him a pardon. Washington's lawyer was outraged when he saw the five-year-old test results for the first time only months ago. "The truth didn't set Earl Washignton free. Why?"

FRONTLINE also looks at the case of Joseph Roger O'Dell. Executed in 1997 for the rape and murder of a Virginia Beach waitress, O'Dell always claimed his innocence. The case didn't die with O'Dell's execution, as the defense, the prosecution, and the courts continued to battle over the right to test the remaining evidence in the case. Death penalty opponents wanted the opportunity to show that the state could well have put an innocent person to death. The state vehemently opposed new testing, hoping a judge would order the evidence destroyed. The prosecutor in the case agreed. "As far as we're concerned, the case is closed. Joseph O'Dell got what he deserved. He got what the law required." He added, "Is there any doubt in your mind that if this sample was analyzed...and it turned out that it was not Joseph O'Dell's blood type or DNA...that there wouldn't be a press conference held announcing to the world that the Commonwealth of Virginia had executed a completely innocent man?"

"He's right," said defense attorney Paul Enzinna. "We will shout it from the rooftops. And it should be shouted from the rooftops. Our government is an open government. It gives people information so that they can make intelligent decisions. And that's what we're fighting for." Unfortunately for Enzinna, however--and for others who sided with him--the last of the DNA evidence that could have proved O'Dell innocent was burned without further testing in March of 2000.

As for Earl Washington, Virginia governor Jim Gilmore ordered a new round of DNA tests on the remaining evidence. The tests, authorized in early June of 2000, could potentially prove Washington innocent of the crime for which he was sentenced to die.

And Roy Criner? His family and other supporters continued to argue for his innocence and campaign for his release. At the same time, a number of reporters, investigators, and lawyers continued to develop new DNA evidence and to argue for new consideration from the courts. In August, 2000, they won. The Texas Board of Pardons and Paroles approved Criner's release and Governor George W. Bush signed the pardon, stating that "credible new evidence raises substantial doubt about the guilt of Roy Criner."