SAN FRANCISCO — A Santa Clara County Superior Court judge withheld crucial information from defense lawyers when she was a prosecutor handling a death penalty case in the mid-1980s, according to a referee’sreport filed last week in the California Supreme Court.

Judge Joyce Allegro, then a deputy district attorney in Santa Clara County, did not tell lawyers representing accused double murderer Miguel Bacigalupo that the prosecution had information, including statements from a confidential informant, that would have supported Bacigalupo’s claim he’d been forced to commit the killings by members of a Colombian drug cartel.