Muhammad, 42, and Lee Boyd Malvo, 18, have been linked to 20 shootings last year, including 13 deaths, in Alabama, Georgia, Louisiana, Maryland, Virginia and Washington, D.C.
Meanwhile, Malvo twice asked for his attorneys before confessing to multiple murders, according to lawyers who want the confession tossed out.
The attorneys filed a motion Friday seeking to suppress the confession Malvo made during six hours of questioning by police on Nov. 7. Malvo is charged with capital murder in the Oct. 14 shooting of FBI analyst Linda Franklin, 47, outside a Home Depot store in Fairfax, Va. He faces trial Nov. 10.
His motion says that before he confessed, he twice asked Fairfax County homicide Detective June Boyle to see his attorneys. Boyle said yes, but added "that police wanted to get some information about him. He said Oklahoma," the motion says.
Lawyers Michael Arif and Craig Cooley argued that Malvo should have been given access to counsel and the confession should be ruled invalid.
"The police lied by telling Mr. Malvo that he would see his attorneys before proceeding to ignore his request," the lawyers wrote.
Prosecutors must respond to the motion by April 21. A hearing on the issue was scheduled for April 28.
In Muhammad's case, attorney Jonathan Shapiro said after a court hearing Friday that the defense has specific information that indicates possible exposure to chemical or nerve agents, but he declined to elaborate. "It's not wild conjecture," Shapiro said.
Shapiro mentioned the chemical exposure during the half-hour hearing in which he successfully argued for the appointment of a mitigation expert, who will look for evidence that might aid Muhammad if he is convicted.
Shapiro mentioned Muhammad's service as a Gulf War veteran and "possible exposure to nerve agents and chemical weapons while he was there. There's a whole lot about this man we need to investigate thoroughly."
Shapiro said after the hearing that Muhammad served as an Army engineer during the 1991 war.
Muhammad is charged with capital murder in the Oct. 9 shooting of Harold Dean Meyers, 53, of Gaithersburg, Md., outside a gas station in Manassas, Va.. Muhammad has an October trial date.