Prosecutors have written to Mary M. Schroeder, the chief judge of the U.S. Court of Appeals for the 9th Circuit, to question whether one of its judges, Alex Kozinski, "can continue to be a fair and impartial member of any 9th Circuit panel, now or in the future, deciding California capital cases" because he once met in prison with death row inmate Michael W. Hunter.

Until a panel of judges can investigate further, state prosecutors said, Kozinski should be barred from hearing any California death penalty cases.

It is a demand without precedent, several legal scholars said. In the history of the federal courts, they said, they know of no occasion when a federal appellate judge has been disqualified from hearing an entire category of cases even on a temporary basis.

Schroeder has asked Kozinski, a Reagan appointee and prominent conservative, to respond to the state's letter. Thus far he has declined.

"I wrote to him and asked him to tell me what happened," Schroeder said Friday. "I can't comment further until I have heard from him, and I haven't heard from him."

In an interview, Kozinski, who gave the Los Angeles Times a copy of the prosecutors' letter, insisted that he has done nothing wrong.

If a case involving Hunter ever came before his court, he would not take part, he said. "I certainly don't think it will affect my judgment" on other capital cases, Kozinski said about his meeting with Hunter.

In his 17 years as an appellate judge, 49 men have been executed in the seven states overseen by the 9th Circuit that have death rows. Kozinski has not voted to block any of them.

"If anyone is going to go after me for the things I have said, I think it would be the other side," he said.

Kozinski's 1997 article for the New Yorker magazine, in which he expressed a degree of ambivalence about the death penalty but stated unequivocally that some murderers deserve it, caught the attention of death row prisoner Michael Hunter, who has since been retried and sentenced to life in prison. The two corresponded and met in 2001 when Kozinski visited San Quentin.

The visit, he said later, was a chance to "see what the inmates look like. Look in their eyes."

"I can go meet a businessman any time," the judge explained. "Meeting someone who has spent time on death row seemed like something I shouldn't pass up."

Judges serving on an appellate court "seldom see the parties," he added. "The facts are like shadows on the wall. They happened a long time ago, and then they are resurrected in trial court. Then we see a transcript. Most of the human quality gets desiccated out of it."

During the visit, Kozinski and Hunter discussed three of the few cases in which Kozinski had sided with California inmates who were seeking to have death sentences overturned, according to a prison official, who said the two also talked about the case of a fourth inmate, Richard Phillips, whose case Kozinski was not involved with. Hunter denied any mention of Phillips.

Asked about the cases they discussed, Kozinski said that he is "not embarrassed by anything I said" but declined to go into detail about the conversation.

At a minimum, the visit created an appearance of a conflict of interest, said Peter Siggins, the state's chief deputy attorney general for legal affairs. Beyond appearances, he wrote in a letter to Schroeder, "we question whether Judge Kozinski's interest in these cases has become so personal that it might interfere with his ability to remain neutral in these cases, or, for that matter to remain neutral in any other California capital case."

Kozinski's 9th Circuit colleague, Stephen Reinhardt, who rarely votes to uphold a death sentence, called the prosecutors' letter "ludicrous."

"When you see them investigating the most publicly outspoken supporter of the death penalty" on the appeals court, "and seek to have him disqualified," Reinhardt said, "they have to be nuts."