FALL RIVER, Mass. — George Perrot has spent almost 29 years in prison since being convicted of raping an elderly woman based in part on a single strand of hair.

Now he’s hoping a recent acknowledgement by the FBI on the limits of microscopic hair analysis will prompt a judge to grant him a new trial.

The hair in question was found in the Springfield home of a 78-year-old woman in 1985.

At Perrot’s trial, an FBI agent testified in no uncertain terms that the hair was a match for Perrot’s.

But last year, the U.S. Department of Justice flagged Perrot’s case as one of hundreds that involved erroneous statements from FBI agents about hair analysis.

The FBI now acknowledges that the science is not conclusive and uses it only in conjunction with DNA testing.

Perrot, who was 17 at the time of his arrest, has always denied raping the woman.

Over the years, his conviction was overturned twice based on grounds unrelated to the hair, but both times a higher court reinstated it.

DNA evidence was not used in trials until the late 1980s, and the hair has since been lost.

On Friday, Judge Robert Kane began hearing evidence in what is expected to be a multiday hearing on Perrot’s motion for a new trial.

Microscopic hair analysis had been used at trials for decades, but a 2009 report from the National Academy of Sciences described testimony identifying a particular defendant through hair analysis as “highly unreliable.”

In 2012, the Justice Department began a review of criminal cases after a string of exonerations in cases in which microscopic hair analysis was used.

In April, the government said that of the 268 trials reviewed so far, investigators found erroneous statements from FBI experts in nearly all of the cases.

The Innocence Project, a Boston law firm and The Schuster Institute for Investigative Journalism at Brandeis University have been working to clear Perrot.

Prosecutors contend that an FBI expert’s testimony about hair analysis at Perrot’s trial wasn’t as distorted as Perrot’s lawyers say it was.

They also believe there was enough evidence to convict Perrot even without the hair evidence.

Perrot’s 76-year-old mother, Beverly Garrant, listened in court Friday as her son’s lawyers tried to demonstrate the unreliability of microscopic hair analysis.

She said she strongly believes her son is innocent and has more hope than she’s ever had that he could be freed.

“I’d like to see my son have another chance to relive his life,” she said. “I just have hope.”