HARTFORD, Conn. — A Connecticut judge on Wednesday ordered a new trial for Kennedy cousin Michael Skakel, who was convicted more than a decade ago of murdering a teenage neighbor, his defense attorney’s office said.

Skakel’s attorneys had argued before state Superior Court Judge Thomas Bishop that his previous defense attorney, Mickey Sherman, did not competently defend him.

The judge granted Skakel a new trial, according to the office of his current defense attorney, Hubert Santos. Representatives of the court could not be reached for comment.

Skakel, 53, is the nephew of Ethel Skakel Kennedy, widow of slain U.S. Senator Robert Kennedy.

He is serving 20 years to life in prison for the bludgeoning death in 1975 of Martha Moxley, his neighbor in Greenwich, Connecticut. He was convicted in 2002.

Both Skakel and Moxley were 15 when she was beaten to death with a golf club. Her body was found on the lawn of her parents’ home in the affluent New York City suburb.

Skakel, who has maintained his innocence, was arrested in 2000. He was unsuccessful in his bid to be tried as a juvenile.

Appearing on CNN, Dorthy Moxley, the victim’s mother, said she remained convinced that Skakel was guilty.

“I have not given up, and I do believe Michael Skakel killed my daughter,” she said. “I don’t believe there’s any doubt in that. He convicted himself practically, and there has been absolutely no new evidence that means anything since the trial.”

In 2006, the U.S. Supreme Court declined to hear an appeal by Skakel seeking to overturn his conviction on grounds that his constitutional rights had been violated because Connecticut’s five-year statute of limitations, in place at the time Moxley was killed, had expired when he was charged.

In 2009, lawyers for Skakel unsuccessfully sought a new trial to overturn the conviction, saying new evidence implicated other men.

He lost a bid for parole a year ago.