A young women accused of killing a 13-year-old girl testified in an Edmonton courtroom Friday that she stabbed Nina Courtepatte, but she thought the girl was already dead.

Michael Briscoe, 36, and Joseph Laboucan, 21, are on trial for thekidnapping, aggravated sexual assault and first-degree murder of Nina Courtepatte in April2005.

The 18-year-old witness who testified Friday also faces the same charges, but has yet to go to trial. She can't be named under the Youth Criminal Justice Act because she was a youth at the time she allegedly committed the crimes.

The young woman told the court thaton the afternoon of Nina Courtepatte's death, she was driving around with a group that included Laboucan and Briscoe.

Laboucan told her they were going to kill someone that night and asked if she wanted to join, she testified. She told the court she thought he was joking.

Grisly attack on girl described

After picking up Courtepatte and her friend at West Edmonton Mall, the group drove to what she thought would be a bush party, the 18-year-old testified.

She described to the court how Laboucan and a younger man had sex with Courtepatte in a deserted field outside Edmonton. The 13-year-old girl was choked with a wrench, hit with a sledge hammer and eventually stabbed with one of the throwing knivesthat werein a backpack, the witness testified.

The woman told the court she also stabbed Courtepatte with one of the knives, but she thought the girl was dead at the time because she had stopped moving and gurgling.

5 people charged in Courtepatte's death

Courtepatte's bruised and bloody body was found on the Edmonton Springs Golf Course in April 2005.

Briscoe and Laboucan are being tried before a judge alone in Alberta's Court of Queen's Bench. The trial is expected to last a month.

They are among five people charged with the girl's murder, but unlike the other three, they were adults at the time of her death.

A 19-year-old man has already pleaded guilty to first-degree murder. Two young women, including the 18-year-old witness and a 19-year-old, are charged with kidnapping, aggravated sexual assault and first-degree murder, but haven't yet goneto trial.

The trio can't be named under the provisions of the Youth Criminal Justice Act.