NEW HAVEN, Conn. – Kennedy cousin Michael Skakel is going back to court this week in a bid for a new murder trial, adding yet another twist to a case that has spawned decades of intrigue.

Skakel, a nephew of Ethel Kennedy, is serving 20 years to life in prison after he was convicted in 2002 of bludgeoning Martha Moxley to death with a golf club in their wealthy Greenwich neighborhood when they were 15.

Skakel, 47, is seeking a new trial based on a claim by one-time schoolmate Gitano “Tony” Bryant implicating two of his friends in Moxley’s 1975 killing.

Bryant, whose claim surfaced in 2003, said he was with two friends from New York in Greenwich 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 the two later told him, “We did what we had to do” and “We got her caveman-style.”

Prosecutor Jonathan Benedict has called Bryant’s account “a complete fabrication.”

Skakel’s attorneys say a jury should hear the allegation.

“The petition for new trial raises substantial issues relating to new evidence never before considered by a jury or a court,” said Skakel’s attorney, Hope Seeley. “Certainly, if this new evidence had been presented to a jury, Michael Skakel would not have been convicted. Michael Skakel is innocent, and we will fight his wrongful conviction and incarceration.”

The victim’s mother, Dorthy Moxley, said she remains convinced that Skakel killed her daughter.

“I really wish we didn’t have to go through with this again,” she said.

To win a new trial, Skakel’s defense must show that Bryant’s account is evidence that was not available at the time of his trial and that it likely would have changed the verdict.

“It’s a very difficult burden,” said Hugh Keefe, a defense attorney in New Haven.

Prosecutors say their witnesses will testify that Bryant was not in the neighborhood the night of the murder and did not know Moxley. They also plan to call Skakel’s trial attorney, Michael Sherman, to question him about his knowledge of Bryant’s account before the trial.

Skakel’s defense plans to call his cousin Robert F. Kennedy Jr. and others to testify that the men knew Moxley and had been to Greenwich, including one woman who says Bryant told her he was in the neighborhood the night Moxley was murdered and knew Skakel was not guilty.

Unlike his trial, the hearing will be televised. It is expected to last one to two weeks.

Skakel is incarcerated at the maximum-security MacDougall-Walker Correctional Institution.

“I would say he’s not doing that great,” Kennedy said. “He misses his son particularly. The prison he’s in is a very rough place. He’s been threatened. He’s had run-ins with some people.”

Skakel’s older brother, Thomas, was an early suspect because he was the last person seen with Moxley, an attractive, popular blonde. Investigators also focused on Kenneth Littleton, a Skakel family tutor.