A shocked Edmonton courtroom heard a teen confess in an audio recording to the murder of two Strathcona County residents four years ago. 

The boy, now 17, is charged with shooting and beating Susan Trudel and Barry Boenke 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, hoping to gain a confession that could be used in court.

On the tape, recorded Mar. 30, 2012 , the teen, then 16, got into a car driven by a man he believes is a crime boss, but was actually an undercover police officer.

The teen began by bragging about his sexual prowess, but then, without any prompting or encouragement, he began to talk about the night of the murders, suggesting he targeted the couple because he had been told they had a freezer filled with crack cocaine.

Couple smoking crack cocaine, teen says

When he and a companion arrived at the acreage, the couple was outside smoking crack, he told the officer.

The teen claimed he shot the man and woman with two bullets each, beating Boenke with a 2X4 and dragging Trudel's body into the house where he struck the back of her head with an axe.

"There was a rifle — I think it was a .30-.30 or a .20-something — it was a long-barrel rifle," he said on the tape. "I had a handgun right; a .22 I found in the bunch of trailers.

"And I used that rifle bullet in the handgun to commit the crime because I knew it would f--- the cops over."

The officer led him on. "Oh that's smart," he said.

"And the reason I did that dragging that body — because they know that a 14-year-old can never do that."

"That's a smart way of thinking," the officer said.

The teen continued. "I drug her up the stairs — you can get those plastic things over your shoes so you don't leave your footprints."

He then bragged about getting rid of the evidence.

He claimed he took the gun apart, bleaching the parts and throwing them in a ditch. He also claimed he bleached the axe to get rid of all the blood. 

Teen fears companion will turn him in

The only regret the teen admitted to is that another 14-year-old boy was with him at the time of the murders, a fellow runaway from the nearby Bosco Group Home.

On the audio tape, he said the other boy didn't do anything, that he was scared.

But he was convinced the teen would rat him out, and told the supposed crime boss, "I want him gone because he knows exactly everything."

The second teen, who no longer faces charges, is expected to testify at this trial. 

Many of the details the accused outlines on the tape, however, do not match the evidence that's been heard so far at the trial.

No murder weapons have ever been found. And court has heard there was no evidence the axe was used in the slayings or was ever bleached.

Also no trace of crack cocaine was found in either victim's system, nor was crack cocaine found on the property.

The conversation took place about nine months after the original charges against the teen had been suspended.

By that time, the teen had already sat through a preliminary hearing where he was able to see and hear much of the evidence police had been gathered from the crime scene.

It will be up to the judge to decide if the evidence gathered during the "Mr. Big" sting can be used in the trial.

The tape was played Monday during a voir dire — a trial within a trial. The teen's lawyer has already served notice that she plans to challenge the admissibility using a Charter of Rights application.

With files from CBC's Janice Johnston