Just over three years after the killing, the teen on Monday pleaded not guilty in Brisbane Supreme Court to murder by aiding or encouraging an older boy.
The teen, who cannot be named as he was a juvenile at the time, was part of a confrontation between two groups in a street in the Logan suburb of Underwood, south of Brisbane, at 1am on February 24, 2023.
Minutes later, Aiden Rhys Bower-Miles, 20, lay dying in a nearby paddock with a deep stab wound.
Most people would be familiar with handing someone a kitchen knife intending to get them to help with the cooking, crown prosecutor Toby Corsbie told the jury.
"What is alleged in this case doesn't happen in the kitchen. It happens out on the street at around one o'clock in the morning as two groups unknown to each other start coming together," Mr Corsbie said.
"Words were exchanged and a fight broke out."
In that context, "what would you know someone was to do if you handed them a knife?" Mr Corsbie told the jury.
The teen who stabbed Mr Bower-Miles was not on trial, the jury was told.
A boy aged 16 at the time was accused of stabbing Mr Bower-Miles with intent to kill or cause him grievous bodily harm.
Justice Elizabeth Wilson earlier told the jury they would have to determine if the 16-year-old had committed murder or manslaughter
They would then decide whether the then-15-year-old was also responsible via allegedly giving him the knife or encouraging him to fight knowing he was armed.
Mr Corsbie said multiple witnesses saw the teen defendant hand a knife or metal object to the older boy before Mr Bower-Miles was stabbed.
An autopsy revealed five sharp-force injuries to Mr Bower-Miles's left arm consistent with defensive wounds inflicted by a sharp object, the jury heard.
The fatal wound was an 11cm-deep cut to his collar bone area that severed his subclavian artery and penetrated his lung before terminating at the spine.
The wound impaired Mr Bower-Miles' breathing and ultimately proved fatal, Mr Corsbie said.
Defence barrister Amelia Anderson asked the jury to keep in mind how young her client was at the time.
"This case starts with two teenagers minding their own business," she said during a brief opening statement.
"The law protects those who find themselves confronted by seven adults, mostly intoxicated, who insist on confronting a couple of boys."
The barrister told the jury they would see CCTV evidence of the fight's short duration.
"Do you think a 15-year-old actually had in that rapidly developing situation any ability to know that his friend intended to kill?" Ms Anderson said.
The trial is due to continue for another six days.
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