Court hears death of Seb O’Halloran was ‘a violent act that occurred in the context of (the girl’s) anger towards (her boyfriend)’

A teenage girl who is on trial for murder allegedly lashed out at her boyfriend before turning her knife on her boyfriend’s mate who was caught up in the fight.

Seb O'Halloran was stabbed to death in Mildura in 2023.

A Mildura teenager was fatally stabbed after he was caught up in a fight between a mate and his mate’s girlfriend, a jury has been told.

Seb O’Halloran, 19, from Irymple in the state’s far northwest, was killed after he was stabbed in the chest with a kitchen knife at a Mildura home in the early hours of October 21, 2023.

A girl, who cannot be named because she was 17 at the time, faced the first day of a Supreme Court trial on Monday, accused of the building apprentice’s murder.

In his opening address, Crown prosecutor Jordan Johnston said Mr O’Halloran was killed after he was caught up in a fight between the girl, now 18, and her boyfriend who had been cheating on her.

Mr O'Halloran was a building apprentice.

“That infidelity ... the Crown will say to you at the conclusion of this trial provides important context for (her) actions,” he said.

The court heard the girl and her boyfriend, then 18, moved in together in September 2023 before she learnt he had been cheating on her about a week before Mr O’Halloran’s death.

On the night of the alleged murder, Mr Johnston said the young couple met up with friends at The Corporate Moose pub but went their separate ways after an argument.

The girl later returned home with friends, he said, where she was recorded on a doorbell security camera berating her boyfriend, saying things such as “f--k you”.

Mr O'Halloran was caught up in a fight between a mate and his mate’s girlfriend.

She allegedly stole her boyfriend’s hidden cash and offered it to her friends, slashed the tires of his work van and cut holes in his clothing.

Still at the pub, Mr Johnston said her boyfriend watched the security footage on his phone before he enlisted his friend Mr O’Halloran and returned home to break-up with her.

The prosecutor said a fight broke out after the boyfriend told the girl “we’re done”.

The girl allegedly tried to punch him before he grabbed her hands and pinned her down.

She was allegedly shoved into a room before she retrieved a kitchen knife and walked down a hallway towards her boyfriend.

The jury was told Mr O’Halloran, who had tried to keep out of the fight, was in the girl’s way.

“(She) walked up behind Seb and said words to the effect of ‘move’,” Mr Johnston said.

When he refused, the girl allegedly said “I’ll do it” before stabbing him in the chest.

Her boyfriend allegedly grabbed her and shoved her outside before calling triple-0.

With the knife still embedded, the court heard Mr O’Halloran also called emergency services before he collapsed in a pool of blood and died.

“The Crown will say this was a violent act that occurred in the context of (the girl’s) anger towards (her boyfriend),” Mr Johnston said.

In her address, defence barrister Sharon Lacy SC said her client did not deny she stabbed her boyfriend’s mate but claimed it was in self-defence.

She said the girl had developed a cocaine habit as a result of her boyfriend’s drug dealing, with their relationship to be a “central feature” of the trial.

The boyfriend and Mr O’Halloran, she said, were also violent.

“The defence position is that she was in a house alone with two men, she had reason to fear both of them and she did what she felt she needed to do in the moment,” she said.

The trial, before Justice Rita Incerti, continues.