The lawyer for a 22-year-old Santa Rosa man on trial in the slaying of his father argued Friday his actions amounted to voluntary manslaughter, not murder, because he was in a psychotic frenzy at the time.

Attorney Karen Silver told jurors that Houston Herczog was suffering from a mental disorder that impaired his ability to form the requisite intent to murder Mark Herczog, 63.

"Somebody did this who couldn't be in his right mind," Silver said in her closing argument.

However, Silver said even if jurors believe Herczog was exaggerating his delusions to doctors they could find that he acted in the heat of passion after being provoked by his father, who Herczog said accused him of incest with his divorced mother.

Under the law, she said someone who is provoked in that way can only be found guilty of voluntary manslaughter.

"Anyone would have a passionate response to that," she said.

Prosecutor Bob Waner disagreed, arguing Herczog showed deliberation and premeditation in arming himself with a knife and stabbing his father at least 60 times.

As his dad lay near death on the floor, Herczog smashed his head with a heavy guitar amplifier, he said.

As for his motive, Waner said it was difficult to define but concluded that it had something to do with being confronted by his father for stealing his mother's prescription stimulant, Adderall, which he said is known to trigger aggressive behavior.

He characterized their last conversation as a "concerned, disciplined father wanting to confront his ne'er-do-well son."

"It pissed him off," Waner told jurors in his closing. "He grabbed a knife and he killed his dad."

The comments from both sides came at the end of a weeklong trial for Herczog, who has pleaded not guilty by reason of insanity to the slaying in the kitchen of their Rincon Valley home in November 2011.

Jurors began deliberations late Friday. If Herczog is convicted of murder or voluntary manslaughter, a second trial would be held to determine if he was sane.

He could then be sentenced to up to 25 years to life in prison or placed in a mental hospital.

Herczog, who confessed to the killing, maintains he was suffering delusions and hallucinations brought on by mental illness.

Herczog was examined by three doctors who found he suffered from schizophrenia at the time of the attack.

A fourth doctor hired by the District Attorney's Office said he was in a drug-induced psychosis.

Family members reported his behavior deteriorated not long after he graduated from Santa Rosa High in 2009 and began attending Santa Rosa Junior College.

His father's sister, Annette Herczog Keys, testified about his increasing isolation and changing manner. She came away from a visit a few days before the killing with the distinct feeling something bad was going to happen, Silver said.

She said she would not have testified on his behalf if she thought the killing was because of drugs.

The defense also called psychiatrist Donald Apostle, who testified Herczog's perceptions were colored by his psychosis. The night of the killing he thought his father was a plastic simulation who was mocking about his relationship with his mother and speaking in code.

The doctor found the attack was not caused by taking Adderall, which was in his blood in only small amounts.

Waner questioned the doctor's findings, suggesting Herczog could have been faking his condition. Even if he suffered a mental disorder, it doesn't explain the killing of his father, Waner said.

"Saying he had schizophrenia says nothing about his intent to kill," Waner said.

(You can reach Staff Writer Paul Payne at 568-5312 or paul.payne@pressdemocrat.com.)