Moussaoui, who is 46 and refers to himself in writing as "Slave of Allah," has been a curious character from the moment he was arrested on immigration charges in August 2001 after employees of a Minnesota flight school became alarmed that he wanted to learn to fly a Boeing 747 even though he had no pilot's license. He was in custody on Sept. 11 and pleaded guilty in April 2005 to conspiring with the hijackers to kill Americans.