A B.C. father sobbed as he sat in the witness stand at his murder trial Wednesday and described killing his three children.

Allan Schoenborn told a B.C. Supreme Court judge that he swung a cleaver at the neck of his 10-year-old daughter, Kaitlynne. He said he then suffocated his two sons, eight-year-old Max and five-year-old Cordon.

They'd all had a good day flying kites together, he told the court, but he became convinced that Max was being molested, and he felt he had no choice but to kill them all because no one would help them.

The 41-year-old gasped and cried as he described how he separated the sleeping children and then murdered them.

He told the court that Kaitlynne pulled his hair as he killed her by slashing her neck.

"I told her to go to the white father," he testified.

Schoenborn said he killed Cordon next, suffocating him with a pillow.

"I thought it was going to be quick with Kaitlynne," he told the court. But it wasn't, so he suffocated the boys instead.

Schoenborn said he used a yellow plastic bag to suffocate Max.

He said he then wrote "forever young" on the walls with soy sauce, and "gone to Neverland" in blood on pillows.

Schoenborn said he tried to kill himself, but instead ran to the mountains with the family dog. He was discovered wandering in the woods 10 days later, dehydrated and suffering self-inflicted wounds.

The accused man said he killed his children "for all the right reasons, I did it for them, my children."

"I gave my children up to be in a better place," he told the judge, who is hearing the case without a jury.

He is charged with three counts of first-degree murder in the deaths of the children, whose bodies were found by their mother in their Merritt, B.C., home in April 2008.

The defence is arguing that Schoenborn should be found not criminally responsible for the killings due to mental disorder, but the Crown contends the murders were an act of revenge against the children's mother.

Schoenborn told the judge he spoke with Clarke on the telephone and in person numerous times on the Friday and Saturday prior to their deaths because he wanted to work out their relationship problems.

Clarke earlier testified she was staying at her mother's that weekend and had left the children in his care while she tried to alleviate her own depression.

Schoenborn was asked by his lawyer if it was true, as Clarke said in her testimony, that he sometimes heard voices.

"I don't know how I was hearing them but I know I was hearing them," he said. "I'm hearing and thinking it's inside me ... it's in my nasal or in my mouth. ... They say derogatory things to me that no one else can hear."

He testified that in the days prior to the murders he believed there was a conspiracy to keep his family apart being perpetrated by a government ministry, the police and the school board.

Schoenborn recounted a history of being admitted to psychiatric wards of hospitals, including an incident when Kaitlynne was 16 months old.

Fearing she'd been drugged, Schoenborn crashed his truck while racing her to hospital. Even after it was confirmed she was well, he pushed for further tests until he himself was admitted to hospital.

He also told the judge that he adored his wife but believed she had cheated on him with at least three different men.

Schoenborn has acted bizarrely in court, shouting questions at witnesses and other verbal outbursts from the prisoner's box.

While on the witness stand, Schoenborn said he believes his children have forgiven him. He said he had a vision in the prison courtyard of his daughter coming to him and forgiving him.

"If Kaitlynne forgives me, I know the boys forgive me because I was a little rougher on Kaitlynne," he told the judge.