The US Supreme Court [official website] ruled [opinion, PDF] 5-3 Thursday in Williams v. Pennsylvania [SCOTUSblog materials] that Pennsylvania’s Chief Justice should have recused himself from a death penalty case in which he formerly served as prosecutor. Terrance Williams was convicted of first degree murder in Philadelphia and sentenced to death. Ronald Castillo was the district attorney in Philadelphia during the trial and was subsequently elected to serve on the Pennsylvania Supreme Court [official website]. Williams then appealed his death sentence to the Pennsylvania Supreme Court, arguing misconduct on the part of the Philadelphia prosecutor’s office when Castillo was serving as the district attorney. Castillo did not recuse himself from the case on appeal, claiming that he was not improperly biased. The Pennsylvania court unanimously denied Williams’ appeal, then denied his motion for reconsideration after Castillo retired from the bench. In an opinion by Justice Anthony Kennedy, the Supreme Court vacated the Pennsylvania Supreme Court’s judgment:

Where a judge has had an earlier significant, personal involvement as a prosecutor in a critical decision in the defendant’s case, the risk of actual bias in the judicial proceeding rises to an unconstitutional level. Due process entitles Terrance Williams to “a proceeding in which he may present his case with assurance” that no member of the court is “predisposed to find against him.”

Chief Justice John Roberts filed a dissenting opinion, joined by Justice Samuel Alito. Justice Clarence Thomas also filed a dissenting opinion.

The Supreme Court heard oral arguments [JURIST report] in the case in February. Certiorari was granted [JURIST report] in October.