A judge denied Michael Skakel's bid for a new trial Thursday, rejecting the Kennedy cousin's claim that two other men committed a 1975 killing that sent him to prison, his attorney said.

Superior Court Judge Edward R. Karazin Jr. ruled against Skakel based on a week of testimony in April, said Skakel lawyer Hope Seeley.

Seeley said she was extremely disappointed, citing the quality of the evidence. "We believe Michael Skakel was wrongly convicted, and we will continue to pursue every legal avenue available to us," she said.

Skakel, a nephew of Ethel Kennedy, is serving 20 years to life in prison for his 2002 conviction for fatally beating his 15-year-old neighbor Martha Moxley in Greenwich in 1975 with a golf club.

Prosecutor Susann Gill said she was pleased with the judge's decision.

"The state is grateful to see that the judge didn't find anything in the petition that undermined the reliability of the jury's verdict," she said.

Skakel sought a new trial based on Gitano "Tony" Bryant's claim that his two friends told him they got Moxley "caveman style."

Bryant gave a videotaped statement to a Skakel investigator in 2003, but has since invoked his Fifth Amendment right against self-incrimination. The two men he implicated have done the same.

Robert F. Kennedy Jr., Skakel's cousin, played a central role in investigating Bryant's claim and telling Skakel's attorneys about it.

Prosecutors have said Bryant's claim is fabricated and that nobody saw him and his friends in the predominantly white, gated neighborhood the night of the murder. Bryant, who attended the same private school as Skakel, and one of the men he implicated are black; the other has been described as mixed race.

But Skakel's attorneys said key parts of the claim were corroborated by others and that Skakel deserved a new trial.

Bryant's claim was the latest twist in a case that was improbable from the start, with an unusual murder weapon in a wealthy New York City suburb where violent crime was rare.