A review of homicide convictions stemming from the work of Louis Scarcella, a Brooklyn detective accused of framing suspects, has turned up a stash of old handwritten police notes that could exonerate two men convicted of a murder in 1985. One of the men served 21 years in prison; the other died behind bars.

The notes were in a file tucked away at Police Headquarters and were written by the first detective assigned to the case. They show that two previously undisclosed eyewitnesses saw the September 1985 killing of a man named Ronnie Durant, but they named killers different from the two men who were convicted. The notebook could have affected the verdict; not turning it over to defense lawyers decades ago is a serious violation of the rules of criminal procedure, experts said.

It was the first significant revelation disclosed by the Brooklyn district attorney’s office in the 11 months since it began a wide-ranging investigation into the work of Mr. Scarcella, who worked the streets of Brooklyn in the 1980s and 1990s and is now retired. One of the most successful detectives in New York City history, he has been accused of a variety of infractions, including roughing up suspects, inventing confessions and even pulling informers out of prison to smoke crack and visit prostitutes or girlfriends.

Questions about Mr. Scarcella prompted the previous district attorney, Charles J. Hynes, to review all the murder cases in which Mr. Scarcella’s work resulted in a conviction. But the revelations were so damaging that they contributed to Mr. Hynes’s surprise defeat in both the primary and general election last year. He was beaten both times — once running as a Democrat and once as a Republican — by Kenneth P. Thompson.