CHESAPEAKE, Va. (AP) — An expert on cults testified Friday that sniper suspect Lee Boyd Malvo may have been susceptible to brainwashing by convicted mastermind John Allen Muhammad, partly because of Malvo's childhood in which his mother often dropped out of his life and moved him to various homes.

"Instability is a factor in indoctrination," said Paul Martin, a psychologist and former cult member himself. "People seek reliability from that instability, that sense of insecurity in their life."

Prosecutors objected to Martin's testimony, saying he was not qualified to offer opinions on the relationship between Malvo, 18, and the man he calls his father, Muhammad, 42, but the judge allowed it.

Malvo's lawyers are presenting an insanity defense, claiming Muhammad brainwashed Malvo to the point the teenager could not tell right from wrong.

A social worker who interviewed Malvo in jail several months after the two men were arrested in connection with the three-week sniper spree that killed 10 people in the Washington area, testified Thursday that she was struck by the young man's interest in the film "The Matrix," in which the hero shoots his way out of a computer-imposed world of virtual reality.

Carmeta Albarus said she watched the movie and saw similarities between Malvo and the character Neo, who brings about a massive societal change under the tutelage of a powerful mentor.

"Neo was going to contribute significantly to change of the system," said Albarus, a defense witness. Muhammad fits the role of Morpheus, Neo's mentor, she said.

Albarus was not allowed to discuss Malvo's impressions of the film. However, Malvo himself mentioned the "The Matrix" in an interrogation interview that was played for the jury earlier in the trial.

During the interview, FBI agent Brad Garrett asked Malvo: "Where should I go look, to understand all this?"

Malvo answered: "Matrix."

When Garrett asked if he meant the movie, Malvo said he did and that both he and Muhammad had watched it. "I watch 'Matrix' if you let me be able to watch it, forever," Malvo said. Defense attorneys planned to show a clip of the film.

Malvo is charged with capital murder in the slaying of an FBI analyst during the sniper spree. Muhammad was convicted of capital murder in another of the deadly attacks; the jury in his case recommended the death penalty.

Albarus said Malvo had complete confidence in Muhammad's plan to create a new, righteous society by taking 70 boys and 70 girls of all races to a compound in Canada and that they would then go out and change the world.

"I pointed out how ludicrous the thought was ... but he felt very confident this could be done because we have to start with the children," she said.

The $10 million demanded by the snipers in notes left at the crime scenes would have provided the funds to buy the land and establish the compound, Albarus said Malvo told her. She first interviewed Malvo in March, five months after he and Muhammad were arrested.

The prosecution on Thursday challenged whether the jury should even be allowed to consider Malvo's mental health as a defense. Fairfax County Commonwealth's Attorney Robert F. Horan Jr. said he is contending with "an insanity defense that's like a puff of smoke."

In response to Horan's concerns, Circuit Judge Jane Marum Roush elicited assurances from the defense that at least one of their mental-health experts will testify that Malvo was so brainwashed he could not tell right from wrong.

A clinical psychologist had testified Thursday that Malvo "produced an abnormal neuropsychological examination."

David Schretlen, who teaches at Johns Hopkins University, based his conclusions on the fact that Malvo scored in the bottom 10 percent of the population for tests related to ability to quickly process information. Depression or anxiety could cause those results, Schretlen said, but he said he did not see evidence of that.

Another possibility, he said, is a dissociative disorder, in which a patient loses touch with reality. A dissociative disorder could potentially form the basis of an insanity defense.