A man who implicated two friends in the 1975 murder that sent Kennedy cousin Michael Skakel to prison has invoked his constitutional right against self-incrimination, his attorney and a prosecutor told The Associated Press Thursday.

Gitano "Tony" Bryant declined to testify at his deposition last week in Miami and does not plan to testify at upcoming hearings on whether Skakel deserves a new trial, said Joel Denaro, his attorney.

"After advice of counsel, Mr. Bryant has exercised his Fifth Amendment right to remain silent," Denaro said. "We'll be taking the Fifth Amendment in any and all proceedings."

Bryant's move could complicate Skakel's efforts to win a new trial. Skakel is serving 20 years to life in prison after he was convicted in 2002 of bludgeoning neighbor Martha Moxley to death with a golf club when they were teenagers in wealthy Greenwich.

"What it strongly suggests to us is that Mr. Bryant's story is a fabrication and he is seeking to avoid testifying under oath for that reason," Prosecutor Jonathan Benedict said.

Skakel's attorneys plan to file a motion seeking to compel Bryant to testify, Benedict said. Calls seeking comment from Skakel's attorneys were not immediately returned.

Denaro would not comment on whether Bryant stands by his account.

Skakel, a nephew of Ethel Kennedy, is seeking a new trial based on a claim by Bryant that two of his friends may have killed Moxley. One of the men, Adolph Hasbrouck, earlier exercised his Fifth Amendment right. Skakel's attorneys identified the other as Burt Tinsley of Portland, Oregon.

Neither of the identified men has returned repeated telephone calls. Hasbrouck's wife, who declined to give her name, said at the couple's home recently that the allegation was "a lie."

"He didn't do anything. My husband is a good man," she said.

Bryant attended private school with Skakel when they were teenagers. His allegation surfaced in 2003, a year after Skakel was convicted of killing Moxley in their gated neighborhood in Greenwich when they were both 15.

According to Skakel's attorneys, Bryant said he was with two friends from New York in that neighborhood the night Moxley was killed. According to court papers, Bryant said one friend had met Moxley and "wanted to go caveman on her," and that after he left them that night, they later told him, "We did what we had to do."

The petition for a new trial is separate from an appeal Skakel lost before the Connecticut Supreme Court earlier this year that argued, among other issues, that the five-year statute of limitations had expired when he was charged in 2000. Skakel's attorneys have taken that issue to the U.S. Supreme Court.