"This case is so bizarre and the degree of indoctrination is so great that we would be remiss if we didn't let a jury consider this issue," Craig S. Cooley, one of Malvo's two lead attorneys, said outside the Fairfax courthouse while the insanity plea was being filed. "Indoctrination is a form of mental illness."
"It's a late-blooming insanity, if there is one," Horan said.
The insanity claim gives Malvo's defense the opportunity to ask the jury to find that he was under the Svengali-like sway of the 42-year-old Muhammad, whom he referred to in confessions as his father.
Malvo's lawyers will present the insanity defense to the jury after prosecutors have finished presenting their case. If the defense succeeds, Malvo will be committed to a Virginia mental hospital until psychiatrists find he is no longer mentally ill, Cooley said.
For an insanity claim to succeed, the defense must convince a jury of one of two things: that the defendant did not know right from wrong, or that he did not know the nature, character and consequences of his crime, Horan said.
Such defenses are rare in Virginia and rarely succeed, said James M. Hingeley Jr., the public defender in Charlottesville. He said juries are reluctant to be receptive to insanity defenses, even ones with merit.
"It goes back to the common public perception that insanity is not a good excuse," Hingeley said. He also said that the coercion Muhammad is said to have exerted over Malvo is not enough to justify an insanity defense.
"There would have to be some real disease process to go along with that," Hingeley said. "Just susceptibility to manipulation is far from being a mental condition that would constitute a defense to any charge."
Prosecutors also asked Circuit Judge Jane Marum Roush yesterday to appoint noted psychiatrist Park Dietz -- an expert prosecution witness who has evaluated such criminal figures as Unabomber Theodore Kaczynski and serial killer-cannibalist Jeffrey Dahmer -- to assess Malvo's mental condition. But Roush refused the request.
So at midday yesterday, Prince William County Circuit Judge LeRoy F. Millette Jr. ruled that Muhammad's attorneys are barred from presenting mental health evidence at his capital murder trial, scheduled to start Tuesday.
The ruling is expected to make it much harder for Muhammad's attorneys to save their client from the death penalty, if he is convicted.
They had planned to use mental health evidence at the sentencing stage of the trial, including reports and testimony from their experts who have spent many hours interviewing Muhammad in recent months.
"He is putting the issue on the table that he has some mental problems, and we want to be in a position to contest that," Ebert said in an interview. "It would be very self-serving of him to tell his experts what they want to hear and prohibit us from being able to rebut that evidence."
Malvo, 18, is scheduled to be tried in Chesapeake on charges that he gunned down FBI analyst Linda Franklin , 47, last Oct. 14 in a Home Depot parking lot in Fairfax County. Horan will argue that the motive was to extort $10 million from the government to end the shootings.
Muhammad's trial, on charges that he fatally shot Dean H. Meyers, 53, last Oct. 9 at a Manassas gas station, will take place in Virginia Beach.
Only snippets of it are barely audible or intelligible, despite enhancements, but Walsh told the judge that he thinks they help the defense.
In a written motion, the defense said it sounds as though Malvo told Detective June Boyle that he "might as well protect him," in an apparent reference to Muhammad. The defense contends that Malvo had also rehearsed what he would say to law enforcement.
"It would be the first time in five tapes that there was something exculpatory on there," said Horan.
Sun staff writer Stephen Kiehl contributed to this article.