Prosecutors are appealing a judge's order granting a new trial to a man who spent three decades in prison for a Massachusetts rape conviction based in part on a strand of hair.

George Perrot was convicted of raping 78-year-old Mary Prekop in her Springfield home in 1985. But a judge found an FBI agent's testimony about microscopic hair evidence was flawed and in January granted Perrot a new trial.

Hampden County prosecutors filed a notice in court Tuesday saying they're appealing the judge's order.

The U.S. Department of Justice flagged Perrot's case in 2014 as one of hundreds that involved erroneous statements from FBI agents about hair analysis. The FBI now acknowledges microscopic hair analysis is inconclusive and uses it only in conjunction with DNA testing.

Perrot has always denied raping the woman.