A 15-year-old boy accused of murdering another teen in a Halifax mall parkade this spring allegedly wrote "caught my first body" in rap lyrics he composed in youth jail, a judge said Tuesday during a hearing related to one of his co-accused.

Four teens, whose names are banned from publication, are charged with second-degree murder in the death of Ahmad Maher Al Marrach, 16, who was fatally stabbed on April 22 inside a parking area of the Halifax Shopping Centre.

All four have pleaded not guilty, but one of the teens, who is now 17, wants his trial to be heard separately from the other three as his lawyer intends to call two of them as witnesses.

Judge Bronwyn Duffy agreed to the trial severance request in Halifax youth court on Tuesday, and in doing so outlined some of the allegations involving the four accused, noting video surveillance captured details of what happened in the parking garage.

The evidence includes phone records of a 15-year-old accused of stabbing Al Marrach, along with social media posts he allegedly made before his arrest.

The judge suggested the teen, who was 14 at the time of the stabbing, had allegedly searched about gangs online and, while remanded at the Nova Scotia Youth Centre in Waterville, N.S., wrote song lyrics that included the line, "Caught my first body, I got a receipt."

Duffy said it's alleged the 17-year-old went to the parkade to fight Al Marrach due to a previous dispute, and the three other accused were there as well, with two of them agreeing to help him in his fight with the victim.

The fist fight lasted about a minute before ending, with two of the teens saying they wanted to take Al Marrach's shoes. Some of Al Marrach's friends arrived, and the fight resumed as two accused held up knives, Duffy said.

When it ended, one of the accused, a 14-year-old girl, went to pick up Al Marrach's backpack. The judge said he shoved her, and was then allegedly stabbed in the heart by the 15-year-old.

Duffy said Anna Mancini, the defence lawyer for the teen who will be tried separately, believes the prosecution will argue that even though he wasn't the one who stabbed Al Marrach, he is criminally liable for murder through "common intention."

The judge said Mancini wants two of the teen's co-accused to testify at his trial, including the 15-year-old. The defence plans explore whether the younger teen had a premeditated plan to kill Al Marrach and was an "independent actor."

All the accused are currently in custody. No date has yet been set for the 17-year-old's trial, while the remaining three will be tried in February.