DALLAS — James Giles knew he was no rapist. It has taken nearly 25 years, but with the assistance of DNA testing, yesterday, Mr. Giles cleared his name, becoming the 13th man from Dallas County to prove with genetic testing that he was wrongly imprisoned.

Mr. Giles, who spent 10 years in prison, is seeking to vacate his 1983 conviction. New evidence suggests that another man — also named James Giles — committed the rape. Dallas County prosecutors more than two decades ago knew about the other James Giles, who lived across the street from the victim, but never told Mr. Giles’s defense.

“I lost everything in the world,” said Mr. Giles, 53. “I just thank God we finally got someone to see that I was the wrong guy.”

Branded a rapist, Mr. Giles struggled to rebuild his life when he got out of prison. The skilled construction laborer had a hard time finding menial jobs, and his wife, who stuck with him throughout his prison term, eventually sought a divorce.

The Dallas County District Attorney apologized personally to Mr. Giles yesterday.

Mr. Giles was found guilty in 1983 of participating in a gang rape of a pregnant woman. The victim picked him out of a photo lineup, even though he was bigger and a decade older than the teenage assailant she initially described to police. That identification was the only evidence linking him to the crime.

Examining old files, the Innocence Project found police and prosecutors had learned that a younger, shorter man more closely matching the description — James “Quack” Giles — lived across the street from the victim. He was friends with Stanley Bryant, who confessed to police shortly after the 1982 rape that he committed the crime with two teenage boys named Michael and James.

“That should have led police to the true James Giles, but it was buried,” said Vanessa Potkin of the Innocence Project, Mr. Giles’s attorney.

“Our client was a decade older, and he had prominent gold teeth. He had phone records and restaurant receipts showing where he was at the time of the crime, as well as the word of his mother and his wife. The evidence was screaming out — this is the wrong guy.”

Police had received a tip that a “James Giles” had taken part in the rape and focused on the older Mr. Giles, who was on probation for attempted murder following a fight with a co-worker.

In what Mr. Giles’s new attorneys called a “remarkable chance encounter,” Mr. Giles came face to face with the tipster in jail. The man, Marvin Moore, realized his tip had led to the wrong man’s conviction and has helped Mr. Giles clear his name.

Dallas prosecutors agreed to review the case in 1991 but did not seek to overturn the conviction, citing insufficient evidence. However, recent DNA tests determined that sperm inside the rape victim came from Bryant and a man named Michael Brown who was a friend of the younger James Giles. Brown was later convicted of another sexual assault and died in prison. The younger Mr. Giles went to prison on an unrelated charge and also died while incarcerated.

Last week, Dallas prosecutors disclosed that the ex-husband of the rape victim, who was present during the crime, recently picked the younger Mr. Giles out of a photo lineup. The victim now concedes she is not sure if the older Mr. Giles was the right man.

Dallas County has had more people exonerated by DNA than all but three entire states. Texas, which leads the U.S. in convictions overturned by genetic testing, has had 27, Illinois, 26, and New York, 23. California has had 9 exonerations.

With countless current and former Texas prisoners clamoring for testing to clear their names — including more than 430 in Dallas County — law-enforcement officials predict that the number of overturned convictions will grow exponentially in coming years.