FAIRFAX, Va. (AP) - Lee Boyd Malvo's lawyers said Thursday they will mount an insanity defense at his murder trial in the Washington sniper case, arguing that the teenager was a victim of "indoctrination" by the older John Allen Muhammad.

Defense attorney Craig Cooley said the basis for the insanity defense comes from mental health experts not appointed by the court.

"This case is so bizarre in its facts, and the degree of indoctrination is so severe, that we would be remiss if we failed" to put the sanity issue before a jury, Cooley said.

Cooley said that indoctrination is a form of mental illness and that it will ultimately be up to a jury to decide if it amounts to insanity.

A court-appointed psychiatrist has met with Malvo more than a dozen times, and the prosecutor in the case, Fairfax County Commonwealth Attorney's Robert F. Horan Jr., said Thursday there is nothing in that expert's report that points to insanity.

"It says absolutely nothing about insanity," Horan said. "Apparently it's a late-blooming insanity."

Malvo, 18, is set to go on trial Nov. 10 in the slaying of FBI analyst Linda Franklin outside a Home Depot (HD) store. She was among 13 people who were shot, 10 fatally, during a three-week spree in the Washington, D.C., are last fall.

Muhammad, 42, goes on trial Tuesday in the slaying of man who was pumping gas near Manassas.

Both trials were moved 200 miles to southeastern Virginia.

Muhammad's lawyers have argued that Malvo was the triggerman, while Malvo's defense team has contended that the teenager was acting under the influence of the older man.

Both defendants could be sentenced to death if convicted.

Along with the 13 shootings in Maryland, Virginia, and Washington, D.C., the two are suspected in or charged with shootings in Georgia, Alabama, Louisiana, Arizona and Washington state.