The undercover officer who posed as an underworld crime boss to pry a confession from a teen told a courtroom Wednesday the sting is not tempered because the accused is so young.   

"A murder's a murder," the officer said. "Murder knows no age. The person's still dead."

The officer, who cannot be identified, admitted threatening and faking violence is part of the "Mr. Big" sting including "anything from a minor threat to an execution, extortion or beating."

The teen, now 17, is charged with shooting and beating Susan Trudel, 50, and Barry Boenke, 68, on an acreage east of Edmonton in June 2009 when he was only 14 years old.

Last year, RCMP mounted a so-called "Mr. Big" sting against the teen after murder charges were suspended for lack of evidence.

The sting involves an undercover officer portraying a crime boss in an attempt to gain the trust and later a recorded confession from the target.

On Wednesday, the officer told the court  he spent more than three months building a relationship with the teen.

Court was shown a video shot on April 1, 2012, when Mr. Big and his entourage took the teen back to the acreage near Ardrossan.

In the video, the boy claimed he was hired to kill the couple by a family member, a hit he agreed to do for nothing.

The boy described how he shot Boenke in the head from eight metres away, how he struck Trudel in the head  with a 2X4, frying pan and finally an axe.

The slender, small-boned teen described how he moved the 203-pound Boenke up the stairs of the house so he could place a bloody handprint inside the trailer to throw police off.

On the covertly-recorded video, he laid down in the same position as Trudel was found, all to convince Mr. Big he had committed the crimes.

About 15 minutes later, the teen calmly got back into a car with Mr. Big and lit up a cigarette.

Court has already heard how many of the teens details do not match up to the evidence already entered at the trial.

As well, all the details were offered up to Mr. Big after the teen saw crime-scene evidence at his own preliminary hearing.

The judge must decide whether he'll make use of the undercover evidence to reach a verdict.

With files from CBC's Janice Johnston