A B.C father accused of murdering his three children shocked a silent courtroom on the first day of his trial by blurting out "a couple of brothers in arms" after gruesome images of the tragedy were shown in court.

The outburst came on the first day of the trial for Allan Schoenborn, 41, who is accused of three counts of first-degree murder in the deaths of his children.

It wasn't the day's only disturbing event.

Earlier, videotaped evidence of the crime scene was played in court, showing that the children's killer had scrawled "forever young" in blood above the family's television set in their Merritt, B.C., trailer home.

Close by, the family's two young boys lay dead on a couch, with one boy's arm draped across the torso of the other. Both had apparently been suffocated.

Just down the hall, their sister had been stabbed several times and a butcher's knife was seen nearby. On a pillow, the killer had written "three gone to neverland" in blood.

Earlier in the day, Schoenborn pleaded not guilty to the charges, but it appears that the former roofer's lawyers will raise mental health as an issue in court, CTV Vancouver Bureau Chief Rob Brown reported Thursday.

Reporting from the court in Kamloops, Brown said that the lawyers may ask for a lesser charge as their client apparently suffers from paranoid schizophrenia.

However, the crown has said that Schoenborn planned the murders as a way to get revenge on his common-law wife, Darcie Clarke.

In April, 2008, Clarke discovered the bodies of five-year-old Cordon, eight-year-old Max and their 10-year sister Kaitlynne Schoenborn in the family's trailer.

Schoenborn went missing shortly after the murders, but was found badly dehydrated and frostbitten 10 days later by a local hunter.

Before the deaths of his children, Schoenborn had several run-ins with the law.

Police arrested him three times in the week before the deaths in Merritt, including for allegedly uttering threats at his children's elementary school. He was also picked up on charges of being drunk in public and for an outstanding warrant for driving while prohibited.

There was a restraining order restricting him from contact with his wife, although neighbours said Schoenborn had been staying with the family for about a week.

Following the arrest for uttering threats at the school, Schoenborn was released on bail by a justice of the peace, over the objections of RCMP. The day before the killings, he was seen flying a kite with the children.

A Vancouver family lawyer is lobbying for a tougher child-protection law in the wake of the slayings.

Kathleen Walker says she's drafting `Cordon's Law' to offer children better protection from violence through tougher, far-reaching restraining orders that would see police notified immediately of any violations.

With reports from the Canadian Press