Tay’s Accused Killer Is Mentally Ill, Jury Told : Courts: A psychologist testifying for the defense claims Robert Chan--who allegedly masterminded the 1992 slaying of the 17-year-old student--is suffering from paranoid schizophrenia.

The 19-year-old accused of masterminding the killing of 17-year-old student Stuart A. Tay suffers from paranoid schizophrenia and was convinced Tay had rigged his home with explosives that could detonate at any time, a psychologist testified Monday.

Robert Chan of Fullerton also heard voices in his head, believed that dangerous people lived in his attic and feared that Tay was a member of the CIA and an Asian Mafia gang that Chan believed was following him, according to clinical psychologist Francis M. Crinella.

Crinella told jurors that Chan believed “Stuart Tay had unusual powers and knew information about Robert no one else knew.” Chan’s mental illness left him convinced that “virtually anything that happened was orchestrated by the victim,” Crinella said.

“Someone has it in for me,” Crinella quoted Chan as saying repeatedly.

But under intense cross-examination by the prosecution, Crinella also told the Orange County Superior Court jury that his diagnosis would be flawed if Chan was lying and feigning illness. The psychologist added that the psychiatric disorder does not prevent Chan from knowing that murder is a crime.

Chan is charged with plotting the 1992 slaying because he feared Tay was going to double-cross him in a planned computer heist, according to the prosecution. But the defense contends that Chan’s mental condition caused him to believe that he had to kill Tay before Tay killed him.

No evidence has been presented during the three-week trial that Tay was trying to kill Chan.

The defendant is expected to testify today, and jurors could begin deliberating as early as Wednesday.

Three others charged in the case, Abraham Acosta, 17, of Buena Park and Mun Bong Kang, 19, and Kirn Young Kim, 18, both of Fullerton, will go on trial after Chan’s case concludes.

The key prosecution witness was a fifth youth, Charles Choe, 18, of Fullerton, who pleaded guilty to his role in the slaying and testified against Chan. The accused murderers attended Sunny Hills High School in Fullerton.

Tay, a student at Foothill High School in Santa Ana, was beaten before rubbing alcohol was forced down his throat and his mouth and nose were taped shut. He was buried in Acosta’s back yard.

Crinella said Chan experiences auditory hallucinations and seemed especially fixated on scenes from the television show “Twilight Zone.”

The laugh of a girl who turns out to be a giant alien toying with humans as if they were ants repeatedly plays itself out in Chan’s head, Crinella said. The phrase “To Serve Mankind,” which refers to another episode in which humans find out too late that aliens are interested in eating--not helping--them, also runs through his mind, the psychologist said.

Crinella told jurors that Chan’s family also has a history of mental illness.