A prosecutor has asked a judge for a psychological examination of a man accused of setting a fatal Sioux City fire. Woodbury County court records show the prosecutor filed a motion Tuesday regarding 51-year-old Robert Mahoney. He's pleaded not guilty to charges of arson and involuntary manslaughter in the Feb. 4 fire that killed 51-year-old Wanda Blake. Mahoney's attorney has filed notice that she may use a defense of diminished capacity. The prosecutor's motion says Mahoney has been examined by a mental health expert on behalf of the defense and says that state law therefore entitles the prosecution to have Mahoney examined by a state expert. The records didn't say when the judge might rule on the motion. Mahoney's trial is scheduled to begin Tuesday in Sioux City.