The 18-year-old, who cannot be identified because of a publication ban, told court Tuesday that he and the other boy ran away from the Strathcona County Ranch, a youth treatment facility run by Bosco Homes, on May 31, 2009.
The boys were in the group home for allegedly vandalizing a school.
The pair — both 14 at the time — drank some vodka, broke into several vehicles and trailers in a nearby storage lot and shot a dog with a pellet gun. They then stole a pickup truck belonging to one of the victims, 68-year-old Barry Boenke.
But the teen testified the pair never saw Boenke or his 50-year-old friend, Susan Trudel, on the rural property where they found the truck. The bodies of the man and woman were found shot and bludgeoned there the next day.
Crown prosecutor William Wister called the teen as a witness but didn't appear prepared for his answers. Wister asked him if the other boy went to the trailer where Boenke and Trudel were killed.
The teen said the other boy wanted to go check out that trailer. "I told him not to."
He said the boy jumped in the truck with him and they drove to Edmonton.
"We did not go into that ... trailer," the teen mumbled.
He spent less than an hour testifying before Wister told a judge he needed time to reassess his position with the witness. After a break, he repeatedly asked the teen if he saw the killings.
"No, I did not," the teen said several times.
Court of Queen's Bench Justice Brian Burrows said he will decide Wednesday whether the Crown can question the teen on statements he gave to RCMP during a so-called Mr. Big sting.
Wister said the teen admitted to undercover officers that he witnessed the killings and the evidence is key to the case.
Court has heard Mounties targeted both boys in Mr. Big operations last year.
RCMP had initially charged both boys with first-degree murder but the charges were stayed following pretrial hearings. A judge ruled a statement made by one of the boys was inadmissible and prosecutors admitted they had no case without it.
Last May, following the Mr. Big stings, the Crown reactivated the case against the one teen and charged him with second-degree murder. The accused teen, who turns 18 next month, is being tried as a youth.
News reports during the trial have said police posed as gangsters and recruited the accused teen, paying him $2,000 for work that including testing out a stolen video game. They also took him to his first music concert and bought him clothes and food.
He eventually gave the officers several different versions of the killings that included some facts police knew to be untrue. The judge has not yet ruled whether he will consider those statements.
Defence lawyer Mona Duckett argued Tuesday that the two-month Mr. Big sting targeting the teen witness was "abusive and coercive." She said the boy often teared up as he was pressured by undercover officers to talk about the killings and he also got some facts wrong.
The teen witness told court he lives in Calgary but is homeless. He has no job and makes money through illegal activities. He is currently in custody on other charges.
The trial earlier heard there is a lack of forensic evidence linking the boys to the crime. Their DNA was not found at the scene and there was no blood or gunshot residue on their clothes.
The gun that killed Boenke and Trudel has also not been recovered.
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