DNA evidence cleared its 200th person in the United States yesterday, another milestone for a technology that has not only reversed convictions but also prompted a more critical look at flaws in the justice system, from crime-lab work to the investigation of arson cases.

The details of the latest exoneration are typically nightmarish: Jerry Miller served 25 years for a rape conviction and had already been paroled when DNA tests showed he could not have been the man who attacked a woman in a Chicago parking garage.

What is also troubling is how common these exonerations have become since the first reversal in 1989. It took 13 years to reach the first 100 DNA exonerations, but just five to double that number. For prosecutors, judges and defense lawyers, the exonerations raise a larger question: How many others, innocent of their crimes, are behind bars?

Advocates for extensive changes in the way cases are investigated and prosecuted see the 200 as the tip of a huge iceberg and use the word epidemic.

Prosecutors bristle at the characterization. They agree that a single person wrongly convicted is an injustice that cannot be tolerated, but they say they see the problems as few and fixable.

Still, while there is deep disagreement on the scope of the problem, there is a growing common ground that the justice system has flaws that need to be fixed.

"We like to believe that the jury spoke the truth - that's what the verdict means, that it's pretty much a foolproof system," says I. Beverly Lake Jr. "We know that's not true now."

Lake is a retired chief justice of North Carolina's Supreme Court.

Though TV crime shows make DNA seem the answer to all cases, it offers the possibility of certainty in a few kinds of crimes - rape, or perhaps a murder during which the criminal struggled with the victim and left skin or blood evidence that can be tested for genetic material.

But the flaws that exonerations have revealed are common to any number of criminal prosecutions: mistaken eyewitnesses, forensic experts who draw the wrong conclusions, jailhouse informants, hair and blood analysis, misguided arson investigations, fingerprint analysis.

In Miller's case in Chicago, parking attendants who chased the rapist away later identified Miller as the criminal.

Academics and scientists are studying forensic practices that have long been accepted without question. Legal experts, such as Lake, are looking at when it might be wise to leap over procedural hurdles that are designed to make it tough to challenge a verdict. Police are rethinking lineups, interrogations, informants.

"We know there are thousands of factually innocent people languishing in prison," said Peter Neufeld, a cofounder of the Innocence Project, the New York-based legal advocacy group that took on Miller's case. "But the overwhelming majority of violent crime doesn't have any biological evidence to test.

"There needs to be, if you will, a revolution in criminal justice to ensure that the other forensic disciplines are as valid and robust as DNA," he said. "There is a tendency on the part of people who are entrenched in the system not to want to lift that rock up."

Neufeld said their nearly two decades of work showed widespread mistakes by law enforcement and huge racial disparities, with blacks much more likely to be wrongly convicted.

The National District Attorneys Association now supports the idea that DNA evidence should be allowed at any time, regardless of whether it is procedurally barred or not, according to Joshua Marquis, district attorney in Clatsop County, Ore.

But he is skeptical of assertions of widespread wrongful convictions. He says 200 out of millions of cases over the last 18 years must be seen as an incredibly small percentage.

In Cook County - where Jerry Miller had his ankle bracelet removed yesterday and declared, "I want to get on with my life, start a life, have a life" - the State Attorney's Office has set up a special DNA unit to reexamine cases with credible claims of innocence.