NEW HAVEN, Conn. — An attorney for Kennedy cousin Michael Skakel said Thursday he was within his rights and had strategic considerations in waiting to file an appeal of Skakel’s murder conviction that claims his trial attorney did a poor job.

Prosecutors urged a judge to dismiss Skakel’s latest challenge of his 2002 murder conviction, saying the claim should have been raised in an earlier appeal and that many of the issues he cites were previously rejected. The 52-year-old nephew of Robert F. Kennedy’s widow, Ethel Kennedy, did not attend the hearing in Rockville Superior Court and there was no immediate ruling.

Hubert Santos, Skakel’s current attorney, said there was no obligation to file the claim earlier and to do so would have forced him to make inconsistent arguments. He said the defense wanted trial attorney Michael Sherman’s cooperation in connection with an earlier appeal and was awaiting details to emerge of Sherman’s tax troubles that would factor into the latest claim.

Sherman served about six months in prison for failing to pay more than $400,000 in income taxes. Sherman pleaded guilty to two misdemeanor counts of willful failure to pay income taxes.

Skakel’s claim argues that Sherman had significant financial problems and didn’t devote enough money to retain investigators and expert consultants. Santos noted that his appeal related to Sherman’s performance came after Sherman pled guilty.

Skakel is serving 20 years to life in prison for the fatal beating of Martha Moxley in wealthy Greenwich in 1975, when they were 15-year-old neighbors. He recently lost a bid for parole after a hearing in which he reiterated his innocence.

Attorneys for Skakel argue in the appeal filed in 2010 that Sherman failed to challenge the state’s star witness by finding witnesses who later rejected his claim that Skakel confessed to the crime. Skakel, who is seeking a new trial, says Sherman failed to obtain evidence from prosecutors and others pointing to other suspects and failed to object to improper closing arguments.

Sherman has said he did all he could to prevent Skakel’s conviction.

Prosecutors say the claim against Sherman should have been raised in an earlier appeal, and contend Skakel is in procedural default.

“He, in the state’s view, waived it at that point,” said prosecutor Susann Gill. “He waived his opportunity.”