New York Times

WASHINGTON — There was something like a consensus at theSupreme Court on Monday that it was not a good idea for a judge to hear a death penalty case he had worked on as a district attorney. But the justices seemed divided over how to fashion a constitutional rule that would bar such conduct yet not require judges to recuse themselves whenever they had had a glancing encounter with the matter under review.

“You want us to get pretty deeply into the issue of a constitutional recusal policy for judges,” Justice Samuel A. Alito Jr. told a lawyer for a death row inmate in Pennsylvania. “So it’s really not enough to just say what happened here was bad.”

The case started in 1986 when Terrance Williams and a friend, both 18, beat Amos Norwood, 56, to death with a tire iron.

Philadelphia’s district attorney, Ronald D. Castille, authorized a capital prosecution of Mr. Williams. “Approved to proceed on the death penalty,” he wrote on a subordinate’s memorandum.

Mr. Williams was convicted and sentenced to death. Mr. Castille went on to serve on the Pennsylvania Supreme Court.

In 2012, as the court’s chief justice, Mr. Castille denied a request from Mr. Williams’s lawyers that he disqualify himself from hearing an appeal based on claims of prosecutorial misconduct by the office he had led, ones that a lower court had accepted. About two weeks before he retired at the end of 2014, Mr. Castille joined a unanimous decision reinstating Mr. Williams’s death sentence.

In a recent interview, Mr. Castille said his role in the case as district attorney had been merely administrative. “I didn’t try the case,” he said. “I wasn’t really involved in the case except as the leader of the office.”

On Monday, several justices seemed frustrated by the reluctance of the lawyers before them to propose a clear and simple standard that would govern all cases in which a judge had had some prior involvement in a case.

Merely having signed an indictment as a prosecutor would not require recusal, said Stuart B. Lev, a lawyer for Mr. Williams. Only “personal involvement in a substantial decision” should count, he said, and then only if that decision figured in the legal issues under appeal.

Ronald Eisenberg, a lawyer in the Philadelphia district attorney’s office, said courts should consider the level of the prosecutor’s involvement and how long ago it happened to determine whether there was “an intolerable probability of actual bias.”

Neither proposal seemed to satisfy Justice Alito. “Recusal is constitutionally required or not,” he said. “I really don’t see a clear rule that would encompass this situation, other than a rule that a judge is required by the Constitution to recuse in any case in which the judge had personal participation as a prosecutor. Anything other than that seems to me to be pretty fuzzy.”

Justice Elena Kagan said that the case was simple. “He made the most important decision that could be made in this case,” she said of Mr. Castille.