Photo: RCMP

Jurors will need to use their common sense in assessing the reliability of an alleged confession by a man accused of killing a 12-year-old girl, a B.C. Supreme Court judge says.

In his instructions to the jury on Friday, Justice Austin Cullen said an undercover police officer posing as a crime boss provided financial and social inducements to Garry Handlen but the man was never threatened.

Handlen has pleaded not guilty to the first-degree murder of Monica Jack near her home in Merritt in May 1978.

Her remains were found 17 years later, on a nearby mountain where Handlen told the supposed crime boss in November 2014 that he sexually assaulted and killed her after abducting her from a pullout on a highway.

He said he threw Jack's bike in Nicola Lake, forced her into the bathroom of his camper and drove his Chevy pickup up a steep hill, the trial heard.

"What I know for sure is I went up a dirt road off the highway, up a hill, somewhere in the Merritt area and I left her body up there," he told the undercover officer in a hidden-camera video recording shown earlier in court.

The RCMP began a nine-month so-called Mr. Big sting in Minden, Ont., in February 2014. Undercover operatives paid for his meals, drinks and hotel stays in cities including Toronto, Ottawa and Halifax and hired him for legal and illegal jobs such as loan sharking.

The trial heard that the final inducement came when the supposed crime boss falsely told Handlen police had DNA linking him to Jack's murder and witnesses could place him at the crime scene but "things could be done to take care of it" if he told the truth.

It's up to jurors to decide the extent to which Handlen could have been influenced to admit to killing the girl, Cullen said.

In the video, Handlen is told a former employee who is sick would take the blame for the murder but he must provide enough details to at least confuse investigators as the group works to get rid of the DNA.

As Handlen begins to talk about what he allegedly did, he repeats five times that he strangled Jack and later repeatedly expresses relief.

"It's a weight off my shoulder now, I've told you. So I'm not the only one that knows now."

Patrick Angly, Handlen's defence lawyer, has urged the jury not to accept the alleged confession, saying it was coerced.

Cullen is expected to finish his instructions on Monday, when Handlen's fate will be in the jury's hands.