BROCKTON — Two convicted killers testified Tuesday that a now-deceased inmate confided to them years ago that he “clipped a guy’’ while on a furlough from prison, with one pinpointing the time of that slaying as May of 1980.

The pair were called to the stand by attorneys for Frederick Weichel — a South Boston man who says he was wrongly convicted of the May 31, 1980, slaying of Robert LaMonica in Braintree – in part because prosecutors did not share a police report identifying another possible suspect.

Superior Court Judge Raymond P. Veary Jr. is holding hearings focusing on whether the report, found in Weichel’s police file in 2010, was crucial evidence that should have been turned over to the defense during his 1981 trial.

Prosecutors contend that the report, which says 10 correction officers believed Rocco Balliro matched a composite sketch of a suspect, was mistakenly placed in Weichel’s file and referred to an unrelated crime.

On Tuesday, the two witnesses, who are serving life sentences for murder, offered testimony bolstering the defense claims that Balliro may have been linked to LaMonica’s slaying. Balliro, who was serving a life sentence for the death of his girlfriend and her 2-year-old son during a 1963 shootout with police, died in 2012.

Patrick O’Shea testified that around 2005 or 2006, he asked Balliro why he had “screwed his life up’’ by escaping briefly when he was released from prison on a one-day furlough in May 1980.

“He told me he had to clip someone,’’ O’Shea said. He said Balliro referred to the victim as “a guy,’’ but O’Shea didn’t press him for details.

O’Shea said he wrote to Weichel’s lawyer after reading a 2013 Globe story mentioning Balliro as a possible suspect in LaMonica’s slaying. He said Tuesday that he wasn’t a friend of Weichel’s, though both are incarcerated at Norfolk state prison, and that he took the stand because he believes Weichel was wrongly convicted.

“I honestly believe that’s an innocent man sitting there,’’ said O’Shea, nodding toward Weichel, now 65, who was seated beside his lawyers.

O’Shea was followed to the stand by Floyd Hamilton, who is also incarcerated at the Norfolk prison. He testified that Balliro told him in the mid-90s that he had “clipped a guy’’ while on furlough.

Hamilton said many inmates were angry at Balliro for jeopardizing the furlough program for others by escaping and he had asked Balliro if he fled the program in search of a woman, prompting his confession. He said Balliro didn’t offer any more details.

The hearings are focusing on the police report and a witness’s identification of Weichel.

A teenager who heard the shots when LaMonica was killed and saw a man flee and jump into a waiting car helped police create a composite sketch of the suspect. He picked Weichel’s mugshot from a photo array as “a pretty good likeness.’’ Later, while driving around South Boston with police and LaMonica’s two brothers, the teen identified Weichel on a street corner.

In response to a public records request by Weichel’s lawyers in 2010, Braintree police turned over copies of everything in his file at the station, including the June 9, 1980, typewritten report, signed by then Braintree Police Detective James F. Leahy. It indicated that someone told him a composite sketch was Balliro and that he’d later interviewed 10 correction officers who agreed it looked like Balliro.

Sydney Hanlon, who prosecuted Weichel in 1981 as a Norfolk assistant district attorney and is now a state appeals court judge, testified Tuesday that she never saw Leahy’s report in connection with the LaMonica slaying and would have turned it over to the defense if she had.

“It was my ethical responsibility,’’ said Hanlon, adding that she provided all of the evidence in the case to Weichel’s lawyer.

Attorney Michael D. Ricciuti, who is representing Weichel for free with assistance from the New England Innocence Project, said, “You didn’t provide him the Leahy report because you never got it?

“That’s right,’’ Hanlon said.

She disputed the defense’s contention that the witness who identified Weichel was standing 185 feet away when he saw the suspect running. The trial judge agreed with the defense in a ruling at the time.

However, Hanlon said, “It was a contested issue throughout the trial.’’

Weichel has consistently maintained his innocence and it is his third bid for a new trial. He has offered letters from convicted killer James “Whitey’’ Bulger to back up his claim.

The letters were filed with the court two years ago in support of the motion to overturn Weichel’s conviction. However, Bulger would not sign an affidavit or testify on Weichel’s behalf.

John R. Ellement of the Globe staff contributed to this report. Shelley Murphy can be reached at shmurphy@globe.com. Follow her on Twitter @shelleymurph.