John Allen Muhammad, the sniper who with an accomplice terrorized Washington, D.C., and its suburbs in 2002, is asking the U.S. Supreme Court to stop his execution.

Muhammad is scheduled to be put to death in Virginia next Tuesday. His attorneys say they will file the appeal today.

Ten people were killed in Maryland, Virginia and the District of Columbia over a three week period in October 2002. Lee Boyd Malvo, a teenager at the time, is serving a life sentence for his part in the crimes. Muhammad's death sentence is for the killing of a man at a Manassas, Va., gas station.

Muhammad's attorneys maintain he is too mentally ill to be put to death.