Josh Cooke wasn't merely a fan of the hit movie "The Matrix." He believed he lived inside The Matrix, his lawyers say.

The 19-year-old had a huge movie poster hanging in his Oakton bedroom and a trench coat like the one worn by Neo, Keanu Reeves's character. He bought a 12-gauge shotgun, similar to one of the weapons Neo uses to fight the "agents" in the movie.

And on Feb. 17, Fairfax County police say, he walked into his family's basement and shot his father seven times with the shotgun and his mother twice. He then called the police -- twice -- to calmly report the killings.

Cooke's fascination with the movie is shared by others who also have been charged with murder. Some high-profile crimes since the movie's 1999 release have allegedly been committed without any obvious motive other than attempts to escape The Matrix.

It is not uncommon for slaying suspects, especially those who are mentally unstable, to raise whatever is hot in popular culture in their defense or in interviews with police. And experts agree that one film alone is unlikely to spark that kind of violence. But to the vulnerable psyches of those who may be mentally ill, films with suggestions of hidden evil and uncertain reality can reinforce paranoia and fear by helping unhealthy fantasy worlds to flourish, the experts say.

The cases in which "The Matrix" has emerged as a central theme span the country. Even last fall's sniper shootings in the Washington region have overtones from the popular science-fiction film, which posits that computers have taken over the world.

"Free yourself of the matrix," sniper suspect Lee Boyd Malvo, 18, wrote in his jail cell. "You are a slave to the matrix 'control.' "

Just this week, in Ohio, a woman who told police that she lived in The Matrix and that "they commit a lot of crimes in The Matrix" was found not guilty by reason of insanity to charges of killing her landlord.

And in San Francisco, a man who believes he was sucked into The Matrix also was found not guilty by reason of insanity on charges that he killed his landlord.

Warner Bros. Pictures, which released the sequel to "The Matrix" this week, said there is no connection between the movie and the killings. In a statement, the studio expressed condolences to the victims of violent crimes. "However," the statement said, "any attempt to link these crimes with a motion picture or any other art form is disturbing and irresponsible."

But many lawyers are continuing to search for any links between art and actuality to defend their clients.

"The Matrix" has developed a huge following in the years since its release, enchanting fans with dazzling special effects and a storyline incorporating aspects of doomsday, man-vs.-machine and biblical allegory. The premise is that in the late 20th century, once man perfected artificial intelligence in computers, the computers took over the Earth, which was mostly destroyed. But the computers continued to "harvest" humans to provide energy, and those harvested humans live in a computer-simulated world: The Matrix.

"He's just obsessed with it," said Rachel M. Fierro, the attorney defending Josh Cooke against charges that he murdered his parents, Paul C. Cooke, 51, and Margaret Ruffin Cooke, 56. "I don't know why he's obsessed. . . . That's one of the reasons we've requested a neutral, independent psychiatrist -- to determine whether he was sane and knew the difference between right and wrong."

A psychiatrist was appointed by Fairfax Circuit Court to examine Cooke after Fierro said in a motion last month that Cooke "harbored a bona fide belief that he was living in the virtual reality of 'The Matrix' at the time of the alleged offenses."

Fairfax Commonwealth's Attorney Robert F. Horan Jr. did not oppose the motion and said it was the first time he had heard of any connection to "The Matrix."

But, he added, "I don't think the movie causes violence. Millions and millions of people have seen it and not killed anybody."

Even experts who have studied the effects of violence in the media do not generally think that one film or one television show can launch such a violent impulse. But they believe that the cumulative effect of media violence in movies such as "The Matrix" can lead to actual crime, particularly in younger people and those already susceptible.

"When somebody commits a violent crime, you can't point to just one cause," said Joanne Cantor, a communications professor at the University of Wisconsin who has studied the effects of television and movie violence. But, she added, "I think these things can have really devastating effects on really vulnerable people. . . . If people are saying they were influenced by that movie, that movie was probably on their mind when they were planning these things."

When "The Matrix" was released, Cooke was 15 and Malvo was 14. Daphne White, head of the Lion and Lamb Project in Bethesda, which advocates against the marketing of media violence to children, said recent research shows that during adolescence, the brain goes through important developmental stages.

"We are selling young children, whose minds are still developing, ever more violent items from ever younger ages," she said. "Even though it's not 'The Matrix' that makes anybody kill, it's the compilation of all the images we're stuffing into children's brains at younger ages."

Psychiatrists have been appointed to examine Malvo, charged in Fairfax with the Oct. 14 killing of Linda Franklin, 47, in the Seven Corners area. Malvo also faces murder charges in Maryland, the District and elsewhere in Virginia in nine other slayings that occurred in a three-week span last fall.

When Malvo was brought to Fairfax on Nov. 7, he was questioned by June Boyle, a Fairfax homicide detective, and Brad Garrett, an FBI agent. Boyle testified recently that she made small talk with Malvo for nearly 90 minutes while they waited for his dinner. A summary of notes made by another detective shows that she asked him what movies he watched.

"Malvo responded he loves 'The Matrix,' " the summary states.

In January, while sitting in his cell in the Fairfax jail, Malvo made drawings and wrote notes around them. In two pages obtained by The Washington Post, he wrote: "Wake up! Free your mind, you are a slave to the matrix 'control.' . . . The outside force has arrived. Free yourself of the matrix 'control.' Free first your mind. Trust me!! The body will follow. Remove fear, doubt, distrust, watch the change then."

Malvo's attorneys declined to comment. They have not indicated whether they plan to argue that Malvo was mentally ill at the time of the sniper shootings.

Such a claim has recently been accepted in two other cases involving "The Matrix." On Tuesday in Butler County, Ohio, Tonda Lynn Ansley, 37, was found not guilty by reason of insanity in the July shooting death of Sherry Lee Corbett, 55, a popular Miami University professor who rented a house to Ansley. Ansley was arrested moments after she shot Corbett in broad daylight in front of several witnesses, and in a statement to detectives, she said, "I started having dreams that I've found out aren't really dreams."

Reeves's character in "The Matrix" believes his initial experience with The Matrix is a dream.

Ansley told police, "That's where you go to sleep at night and they drug you and take you somewhere else and then they bring you back and put you in bed and when you wake up, you think that it's a bad dream."

Craig Hedric, the Butler County prosecutor who handled the case, said that, "in her warped perception," the movie did have a role in the killing. "But I think that's only because she was suffering from a mental illness. I don't think some rational soul is going to be influenced to do that," he said.

Similarly, in San Francisco in April 2000, Vadim Mieseges, 27, killed and dismembered his landlord, Ella Wong, 47, without provocation. In September, a judge accepted his plea of not guilty by reason of insanity, and he was sent to a hospital for treatment.

In his confession, Mieseges "did make reference to being sucked into The Matrix," said Inspector Kelly Carroll, who interviewed him. "He seemed to have stepped through the looking glass," Carroll said, invoking the surrealism of "Alice in Wonderland," adding: "And The Matrix was a real thing to him."

Tonda Ansley of Ohio, who told police she lived in The Matrix, was found not guilty by reason of insanity in her landlord's slaying.Investigators say sniper suspect Lee Boyd Malvo told them that "he loves 'The Matrix.' " In his jail cell, he made notes referring to "The Matrix," writing: "Wake up! Free your mind, you are a slave to the matrix 'control.' "