Seb O'Halloran left a nightspot to support a friend through a break-up and within an hour he was dead, a court has been told.
A woman, who was 17 at the time and cannot be named, is on trial for his murder.
Mr O'Halloran, 18 and a promising motocross rider, died from a fatal stab wound at a Limpidi Drive in northwestern Victoria's Mildura address in the early hours of Saturday October 21, 2023, crown prosecutor Jordan Johnston told the court.
Attending paramedics could not find a heartbeat and the victim was pronounced dead at the scene.
The kitchen knife that killed Mr O'Halloran was still in his chest until after an autopsy was performed, the court was told.
Mr Johnston told the jury it would hear the accused was living in a share house at Limpidi Drive with her boyfriend who was 18 at the time.
He alleged Mr O'Halloran was stabbed by the accused after coming between her and her boyfriend during an increasingly heated and physical altercation.
The jury heard the boyfriend had allegedly sold and supplied the accused with cocaine on the night in question, and that the accused had tried to give away some of his "stash" of money before allegedly slashing his tires.
The prosecutor said Mr O'Halloran had left Setts, a Mildura nightspot, with his friend about 12.35am, to offer support while he broke up with the accused back at the share house.
Mr O'Halloran had stayed out of the argument and increasingly physical altercation between the other two, and called his sister and sister's partner from the living room, the court was told.
The jury heard the accused hit her boyfriend and he pinned her down several times before she was pushed into a room she was using for clothes.
The two became separated and Mr O'Halloran came between them as the accused returned from another room via the kitchen carrying a knife.
The accused allegedly asked Mr O'Halloran to move, which he refused.
"It is the Crown's case is that (the accused) stabbed Seb in the chest with the kitchen knife ... and that he died as a result," Mr Johnston said.
The defence accepted the accused had a role in Mr O'Halloran's death but rejected the Crown's summation of what led up to the incident.
"(She) was holding the knife that entered the body of Seb O'Halloran," defence barrister Sharon Lacy told the court.
"She let go of the knife and it remained in his chest until after autopsy, none of that is disputed."
The accused is claiming self-defence.
"The defence's position is she was in a house, alone, with two men," Ms Lacy said.
"She had reason to fear both of them and she did what she felt she needed to do in the moment."
Mr O'Halloran's death led to outpourings of grief in the Mildura community and a fundraiser for his family has raised more than $30,000 since his death.
