WASHINGTON Sirhan Sirhan lost a Supreme Court appeal Monday that sought to overturn his conviction in the assassination of Sen. Robert F. Kennedy in 1968.

The justices refused without comment to consider claims that Sirhan's defense lawyer was secretly working with the government to win his conviction.

Sirhan's new attorney, Lawrence Teeter of Los Angeles, also argued unsuccessfully that a California judge who was a prosecutor in Sirhan's trial had tainted his appeals. Teeter said that colleagues of U.S. District Judge William Matthew Byrne Jr. should have been disqualified from considering his filings in lower courts.

"What is at stake is not simply (Sirhan Sirhan's) constitutional rights but the integrity of the judicial system and the appearance of justice as the judicial system confronts the truth about an event that changed the entire world," Teeter told justices in court paperwork.

Sirhan is serving a life sentence for killing the New York Democrat just moments after Kennedy declared victory in the California presidential primary.

Sirhan claims that he was hypnotized at the time and that a second gunman might have actually killed Kennedy at the Ambassador Hotel in Los Angeles.

The case is Sirhan v. U.S. District Court for the Central District of California, 02-7246