VANCOUVER -- Family members of a 12-year-old British Columbia girl murdered in 1978 cried, hugged and thanked jurors who found a man guilty of first-degree murder Thursday.

Garry Handlen, 71, told undercover police during a sting in Minden, Ont., that he abducted Monica Jack while she was riding her bike, sexually assaulted and strangled her, but his defence team said the confession was coerced.

As sheriffs led him out of B.C. Supreme Court, Handlen turned to face a woman who yelled: "And that goes for ... trying to kill me!"

The woman, whose name is under a publication ban following a trial in 1979 where Handlen was convicted of sexually assaulting her, wept too as she supported Jack's family.

Jack's mother, Madeline Lanaro, said she would not immediately comment on the verdict. The family will return to court for a sentencing hearing on Jan. 28 and provide victim impact statements.

Jurors began deliberating Handlen's fate on Tuesday after an 11-week trial that heard tearful testimony from Lanaro, who last saw her daughter riding her new bike on May 6, 1978.

The trial heard Handlen confessed during a so-called Mr. Big operation, saying he'd grabbed Jack from a highway pullout in Merritt.

A first-degree murder conviction carries an automatic life sentence with no chance of parole for 25 years.

In a hidden-camera video shown in court, Handlen told the crime boss of the fictitious Mr. Big operation that he grabbed Jack, threw her bike in a lake, forced the girl into the bathroom of his camper and drove up a rough hill where he killed her.

Jack's skull and some bones were found in the area 17 years later.

Her mother told the trial she was driving her old Mustang home with her other children when she saw her daughter on the highway and that the girl waved at them.

"I honked and the kids yelled out, 'Do you want a ride? And she said 'No.' "

The woman who Handlen sexually assaulted said outside court that police called her in December 2014 to say he'd been charged with the first-degree murder of Jack.

"Then everything came back," she said. "The last four years have been hell, very difficult. I haven't been able to hold down a job."

Handlen was arrested and charged after a nine-month undercover operation involving a fictitious crime group that hired Handlen to do legal and illegal jobs such as loan sharking, the trial heard.

Handlen was paid almost $12,000 by the gang that promised him a middle-management job as he was gaining favour with the boss, who told him in the video that police had DNA linking him to Jack's murder but the crime could be pinned on someone else if he provided enough details.

"The bottom line is, they got people that saw you and they got your DNA. That's not good, Garry," the crime boss tells him in a hotel room, in video shown to the jury.

Handlen was also told he would have to travel to British Columbia's Interior with other members of the group to point out the spot where he said he'd abducted Jack so an ailing man taking the fall for him would have that information.

Handlen told the supposed crime boss that he picked up an Indigenous girl and sexually assaulted her, then repeated at least half a dozen separate times that he strangled her before tossing her body behind a log and leaving the area.

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

The boss tells him he could continue working for the group to repay the debt.

"I'm indebted for life now," Handlen says, before repeatedly thanking him.

Handlen's defence lawyers told the jury their client was set up by the RCMP with inducements that had him believing he'd get his dream of a new truck and continue being part of a group he called a band of brothers.

However, the Crown said Handlen had no motivation to confess to a crime he didn't commit and felt relief at having unburdened himself from a secret he'd carried for 36 years.

Outside court, Crown spokeswoman Alisha Adams praised the three prosecutors who worked on the case for four years, adding they showed great perseverance through a difficult case.