The pair were among five teens - aged between 15 and 18 at the time - who were arrested after Jack died in December 2019, barely two weeks before Christmas.

He was stabbed in Surfers Paradise after the five teenagers started a fight because Jack's group was staring at them, the court was told.

Three teens - who can't be named - pleaded not guilty to manslaughter and two counts of grievous bodily harm when their judge-only trial began in Brisbane Supreme Court on Monday.

Jack's family members including his parents Brett and Belinda asked to leave the court room before CCTV footage was shown of the 2019 fight.

Footage showed their son collapsing outside a store holding his chest and slipping on his own blood while trying to regain his footing during the altercation.

Jack died later that night at Gold Coast Hospital.

"The stab wound penetrated his heart and as a result from the bleeding that followed he suffered a heart attack and died," crown prosecutor Todd Fuller told the court.

A 17-year-old member of Jack's group was stabbed twice in the fight, puncturing a lung and causing "significant internal bleeding".

The five teenagers had a BBQ at Surfers Paradise where the knife was used to cook food before they later noticed Jack's party of eight, Mr Fuller said.

The five teens ran down Surfers Paradise Boulevard pursuing Jack's group before stopping them outside Paradise Towers apartment building and asking why they were staring, the court heard.

Mr Fuller said one of the five teens asked Jack's party: "Do you have an eye problem?"

The court was told the fight broke out after Jack was pushed and reacted by flicking a cigarette at one of the teens.

Mr Fuller said a 15-year-old had a knife tucked in his pants and stabbed Jack and his companion during the altercation before being seen on CCTV footage fist bumping an 18-year-old member of his group as they ran off.

"As they run down the street Your Honour can see they fist pump each other," he said of the footage.

The five teenagers then went to the beach and discarded some clothes before departing.

Defence lawyer Greg McGuire described the incident as a "consensual fight amongst two groups of teenagers".

He said a 15-year-old had "essentially gone off on a frolic all of his own and it all happens very quickly".

A teenager - who was 15 at the time of the incident - last week pleaded guilty to murder and two counts of committing malicious acts with intent.

Last month another teenager - who was 17 at the time - pleaded guilty to manslaughter and two counts of grievous bodily harm.

The trial continues.

Australian Associated Press