Dec. 11 (Bloomberg) -- The U.S. Supreme Court reinstated a California murder conviction that had been overturned because the dead man's relatives wore buttons bearing his picture during the trial.

The justices said a federal appeals court was wrong to order a new trial for Mathew Musladin, convicted of killing his estranged wife's boyfriend, Tom Studer. Musladin says he acted in self-defense.

The ruling was unanimous, though the justices differed in their reasoning. The court's lead opinion, joined by six justices, said nothing about the propriety of the buttons and instead focused on the power of federal courts when they consider so-called habeas corpus challenges to state court convictions.

Writing for that group, Justice Clarence Thomas pointed to a U.S. statute that says federal judges may intervene only when state judges improperly apply ``clearly established'' law.

Thomas said that standard wasn't met, given that ``this court has never addressed a claim that such private-actor courtroom conduct was so inherently prejudicial that it deprived a defendant of a fair trial.''

Three other justices -- Anthony Kennedy, John Paul Stevens and David Souter -- wrote separately. Each said he would have reinstated Musladin's conviction while also offering more guidance to lower court judges for future cases.

Kennedy said trial courts should consider banning buttons as a ``preventative measure'' and to ``preserve the calm and dignity of a court.''

`Conveyed the Message'

The 9th U.S. Circuit Court of Appeals ordered a new trial last year, saying the buttons improperly ``conveyed the message that the defendant was guilty.''

The 1994 shooting took place after Musladin arrived at the San Jose home of his wife, Pam, to pick up their son. Musladin confronted Pam, her brother and Studer and eventually fired two shots, the second one ricocheting into Studer's head and killing him. Musladin testified that Studer was carrying a gun and that his brother-in-law was wielding a machete.

At trial, Studer's parents and brother wore buttons several inches in diameter with his photo. A California state trial judge allowed the buttons and a state appeals court upheld that decision.

Musladin then asked the federal courts to set aside his conviction. After a trial judge refused, the San Francisco-based 9th Circuit said Musladin hadn't received a fair trial.

The case is Carey v. Musladin, 05-785.

To contact the reporter on this story: Greg Stohr in Washington at gstohr@bloomberg.net.

Last Updated: December 11, 2006 11:54 EST