SAN FRANCISCO — Under almost any circumstance, asking for a judge’s recusal is a delicate matter. The Arizona federal defender’s office walked into an especially risky thicket Tuesday, asking Judge Susan Graber of the U.S. Court of Appeals for the Ninth Circuit to recuse herself from a death penalty case because of a family tragedy involving her father.

In an eight-page motion for recusal, assistant federal public defender Timothy Gabrielsen argued that the facts of his client’s case bear a strong similarity to the 1974 carjacking murder of Graber’s father, Julius. “The average person on the street or the disinterested lay observer would, if apprised of these facts, entertain a significant doubt as to Judge Graber’s impartiality,” Gabrielsen wrote.