A  psychologist claims Alvaro Castillo was 'floridly psychotic' on the day of his father's murder.

Castillo, 22, is on trial for fatally shooting his father, Rafael Castillo, and opening fire at Orange High School in August 2006.

Defense attorneys are trying to convince a jury that Castillo is mentally insane.

"In my opinion, he was suffering from two severe mental disorders," said James Hilkey, forensic psychologist for the defense. "He was not in touch with reality at that time."

Hilkey said that, as a result of mental illness, Castillo developed a delusional belief system over a period of time.

"This belief system was very real to him," said Hilkey. "He believed it emanated from God. He knew it was against the law to kill, but because of his delusional belief, he was unable to tell the difference between right and wrong."

Deborah Grey, a licensed clinical social worker who evaluated Castillo, finished her testimony Thursday morning, after spending most of the day on the stand Wednesday.

During cross-examination, prosecutors questioned Grey about the mental healthcare treatment Castillo received after a failed suicide attempt in April 2006.

In 2007, Grey conducted interviews with Castillo, his family members, teachers, classmates, and others as part of her evaluation of the defendant.

She testified that there is a history of mental illness in Castillo's family, and that a troubled home life made Castillo afraid to express his emotions.

Jurors have viewed videos Castillo recorded in which he talks about shooting his father in the head and shows the body with a sheet over it on the couch in the living room. They have also heard excerpts from Castillo's journal that detail thoughts of suicide and an obsession with the Columbine school shootings.

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