A Merritt, B.C., father who admitted killing his three children has been found guilty of first-degree murder in their deaths but not criminally responsible for the slayings.

Allan Schoenborn pleaded not guilty to the charges but acknowledged slaying his 10-year-old daughter and two sons, aged eight and five, in April 2008 at a Merritt trailer that was the home of the children and his estranged wife.

The pivotal issue in the trial was Schoenborn's state of mind at the time of the killings. His lawyer argued he was insane and therefore not criminally responsible, while the Crown said he was sane and murdered his children out of revenge against his ex-wife, who had spurned his pleas to renew their relationship.

B.C. Supreme Court Justice Robert Powers, who heard the three-month trial in Kamloops without a jury, found that the killings were deliberate and planned by Schoenborn, but that he was not sane at the time.

"I find on balance of probabilities he was suffering from a disease of the mind," Powers told the court Monday.

Powers rejected the Crown's assertion that Schoenborn killed his children as revenge against their mother.

"I find it unlikely [he] would have killed his children out of anger given the close and caring relationship he had with his children," said Powers.

"Mr. Schoenborn, if anything, was overprotective. The irony is that the real danger to the children was Mr. Schoenborn himself and none of the dangers that he imagined in his mind."

But Powers said Schoenborn's imaginary fears can't justify his crime.

"Any reasonable or rational person would know that was wrong," he said. "However, due to his psychosis at the time he was not able to make that decision."

Schoenborn spoke out twice during Powers's reading of his judgment, saying only, "bullshit."

Powers said Schoenborn must appear before the British Columbia Review Board within 90 days to determine where he will be held.

Outside court, Schoenborn's defence lawyer, Peter Wilson, called the verdict "the right result."

"It shows the system works," Wilson said. "It's clear Mr. Schoenborn was mentally ill. He loved his children. What he did didn't make any sense. He loved them."

The trial heard defence claims that Schoenborn, 41, believed it was his duty to kill the children to protect them from sexual abuse. No evidence was presented to suggest they were being abused.

Psychiatrists testified

Both the Crown and defence brought in psychiatrists to testify. The defence expert said Schoenborn was delusional when he killed the children while the Crown psychiatrist said it was impossible to tell precisely what his state of mind was.

The children's mother, Darcie Clarke, sobbed as she testified about returning to her home to find the cold bodies of Max, aged eight, and Cordon, five, curled up on a couch, and then Kaitlynn, 10, in her bedroom wrapped in her favourite blanket, dead from stab wounds.

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Allan Schoenborn pleaded not guilty to three counts of first-degree murder in the deaths of his children. (CBC)

After the slayings, Schoenborn led police on a nine-day pursuit before he was captured by a hunter in the hills near the southwestern Interior community.

Clarke was fitted with voice-recording equipment by police when she asked Schoenborn in a private jailhouse meeting with him why he had killed their children.

"I thought they were being molested," the court heard Schoenborn saying on the recording.

He promised Clarke he didn't torture the children, but said the killings weren't quick because he didn't know what he was doing.

"It came in one big flood. There was nothing I could do about it if I tried," he said.

With files from The Canadian Press