One day, in the summer of 2001, Keith Turner, a poor, marginally employed ex-convict, was doing what he often did: Sitting in his small rented house in South Dallas, idly watching Court TV.

"They had a guy on there with a case just like mine," he said in a recent interview. "He'd been accused of a rape he didn't do, and his DNA proved it."

Mr. Turner, then 40, had never heard of DNA. And he'd already done his time - he'd been out of prison for more than a decade, having been paroled in 1989.

Mr. Turner, who'd always maintained his innocence, started writing letters to everyone he could think of - to Court TV, the attorney general, the district attorney, the public defender, the courts - asking for help. Asking if he could please have one of these "D and A" tests.

That summer day marked the beginning of the end of a long and awful ordeal for Mr. Turner, who was convicted in 1983 of raping a young mother of three. Mostly through his own perseverance, he got his DNA test in May 2004. It showed that he wasn't the rapist, and two days before Christmas 2005, he received a full pardon from Gov. Rick Perry.

Mr. Turner is one of 12 men convicted of violent crimes in Dallas County to have been exonerated by DNA evidence since 2001. A 13th is about to be cleared.

That's more than in any other county in America. And with Craig Watkins, the new district attorney, poised to review more than 400 other requests for post-conviction DNA tests, the number of exonerations is expected to grow.

The governor's pardon cleared Keith Turner's name and proved to the world that he'd been telling the truth for more than 20 years. And for that, he's grateful.

"God does things for a reason. I know that," he said one evening not long ago, sitting in the dimly lit, simply furnished living room of his southeast Dallas apartment.

Work has been hard to find. He's driven delivery trucks, driven a shuttle bus at the airport, driven cars at a local auction company. But mostly now he stays at home, living quietly off a settlement he received from the state of Texas last year, under a law that provides for compensation to people wrongly imprisoned.

Based on the length of his imprisonment, Mr. Turner was entitled to $81,249.99, according to the comptroller's office. He got half last May and will get the other half in a few days.

"I still don't understand how I got caught up in all this. During all the time I was trying to clear my name, I prayed every night: Lord, please bring the truth out. You know I didn't do this."

On the evening of Dec. 6, 1982, the 33-year-old woman was in her apartment in East Dallas when her son, Luis, told her that he needed clean pants for school the next day.

With some trepidation, she went down to the laundry room to put a load of wash in. Her husband wasn't home, she would testify in Mr. Turner's trial, and she didn't like to be in the laundry room by herself. The apartment complex, near Ross and Henderson, was "not a very safe place," she said.

When she went back a few minutes later to transfer the clothes to the dryer, she testified, a man followed her into the laundry room. "I just had a feeling something could happen," she said.

The man switched off the light, then slapped her hard across the mouth with the back of his hand. When she screamed, he told her, "Shut up, [expletive]." As she pleaded with him not to hurt her, she said, he raped her. Then he ran away.

Almost four months later, she testified, she was at her job - she was a collection agent for a furniture store - when Mr. Turner, then a 22-year-old truck driver for the same furniture company, entered the office and asked to use the phone.

The two didn't know each other, she said, but she immediately recognized him, by his voice and face, as the man who had raped her in December. She told a supervisor.

At Mr. Turner's trial, in September 1983, the woman reiterated her certainty that he was her attacker. She had no doubt. She would never forget his face.

Mr. Turner testified that he didn't know Ms. Sanchez and had never been to her apartment complex. He said that on the night she was raped, he was miles away, with a cousin and a friend at the cousin's house in Oak Cliff, watching Monday Night Football.

The rapist had not worn gloves - Ms. Sanchez told police she distinctly remembered the sharp slap across her face. Yet, there were no fingerprints - indeed, no physical evidence of any kind - admitted as evidence at the trial.

But none of that, apparently, outweighed the power of the victim's unwavering eyewitness identification. And Mr. Turner had made matters worse for himself by hiding under a couch in his mother's home when the police came to arrest him - behavior testified to by a Dallas detective.

"I was scared. So I hid," Mr. Turner said in the recent interview. "I was 22 years old. I was home by myself. The officers were going to send me to the pen for something I didn't do. I just panicked. You'd be scared, too."

The rape victim could not be found to be interviewed for this story. Court documents filed in October 2003 said authorities couldn't locate her or her husband. She was later contacted, around the time of Mr. Turner's DNA test, but her whereabouts today are unknown.

Also unknown, probably forever, is the identity of the true rapist. By the time of Mr. Turner's exoneration, it had been more than 21 years since the crime. With certain exceptions, the statute of limitations for rape in Texas is 10 years. Whether the person who attacked Ms. Sanchez is alive or dead, behind bars or drinking in one, no one knows.

He added: "It's any honorable prosecutor's worst nightmare to find out that a man he prosecuted was wrongfully convicted for any reason. I tried to honorably prosecute every case, based on the evidence - every time.

When the police first questioned Mr. Turner about the rape, his mother, a longtime science teacher for the Dallas and Wilmer-Hutchins school districts, was furious with him, he said.

Mr. Turner's letters, still on file in the clerk's office of the Fifth Court of Appeals of Dallas County, paint a heart-wrenching portrait of someone desperate for help.

Carefully penned in a compact, almost childlike script, they are earnest and eloquent despite their spotty spelling, grammar and punctuation. They're written in the stilted voice that men unaccustomed to suits and ties sometimes adopt in the presence of authority figures.

"Sir, I am not a rapist or a sex offener," he wrote on June 28, 2001, to Bill Hill, then the district attorney. "I am very not guilty of this crime."

"I dont have much money but I give what ever I got just please help please," he wrote on Aug. 20, 2001, to Jane Roden, then the Dallas County public defender.

"I am going to fight till my last breath, sir, I have never hurt a person in my life," he wrote to State District Judge Cliff Stricklin on Oct. 29, 2001.

It was Judge Stricklin, who had taken over the court in which Mr. Turner was convicted years earlier, who made the exonerating DNA tests possible.

After getting Mr. Turner's letters, the judge spoke with him in person. Impressed with Mr. Turner's sincerity, he appointed John Hagler, a well-known Dallas criminal defense attorney, to handle Mr. Turner's petition for a DNA test.

Mr. Hagler last week praised the Dallas County district attorney's office under Mr. Hill for not contesting the request - and for working with him to secure Mr. Turner's DNA test.

"I apologized to him," the former judge said. "I said something to the effect that the system typically works, but in his case, it let him down.

"As long as the justice system is run by humans, there will always be mistakes," he said. "Our job is to minimize those mistakes insofar as possible, and to do all in our power to correct them when we discover them."

"What happened to Mr. Turner is sad. It's a shame. It was flat-out wrong. We can never give him back those years that he spent behind bars. I'm just glad that, years later, we were able to set the record straight and clear his name."

The experience has left Mr. Turner a cautious man. He was at first reluctant to be photographed for this story, saying he didn't want people to know who he was, didn't want anyone knowing his business.

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