Jonathan Sheldon plans to file the clemency request with Virginia Gov. Timothy Kaine next Thursday, his Web site says. He also plans to file an appeal with the U.S. Supreme Court.
Kaine told WTOP-AM, Washington, last month he knew "of no reason why clemency would be granted in this case," but said he would review Muhammad's request. The Supreme Court had no comment.
Muhammad was sentenced to death for the Oct. 9, 2002, death of Dean Harold Meyers, 53, killed while pumping gasoline at a Sunoco gas station near Manassas, Va., during a string of shootings that left 10 people dead and three wounded in Virginia, Washington, D.C., and Maryland.
His execution is scheduled for Nov. 10.
Muhammad's teenage co-defendant, Lee Boyd Malvo, is serving a life sentence without parole for six murders in Maryland.