Two young rugby league players are on trial after a Canberra festivalgoer was left unconscious and nursing a broken jaw, allegedly because of "bad blood" and "rumours" about a woman.
The jury trial of Jese Smith-Shields and Bayley Loughhead, 22, began in the ACT Supreme Court on Tuesday.
Both men have pleaded not guilty to a charge of recklessly inflicting grievous bodily harm.
In his opening address, Crown prosecutor Trent Hickey said the victim and his girlfriend went to Spilt Milk in 2018 expecting a fun day of listening to bands like The Wombats and Peking Duk.
But Mr Hickey said things became tense when the couple came across a group the victim knew from school and from playing football. Both of the accused were among the group.
The tension, Mr Hickey indicated, was the product of rumours claiming the victim had slept with Mr Smith-Shields' ex-girlfriend.
He said Mr Smith-Shields was "immediately aggressive" towards the victim, squaring up and yelling words like, "Do you have something to say?"
The victim responded by saying something along the lines of, "I didn't go near her", according to Mr Hickey.
Mr Hickey said the victim's girlfriend tried to defuse the situation, but she was pushed aside and the victim was knocked to the ground.
He said the victim got up and tried to defend himself, only to be grabbed in a headlock by Mr Loughhead and punched by Mr Smith-Shields until he was unconscious with a fractured jaw.
Mr Hickey told the jury that while the victim was in hospital, Mr Smith-Shields had sent him a message on Instagram apologising and saying: "That's the last thing I wanted to happen."
Defence barrister Beth Morrisroe, representing Mr Smith-Shields, told the jury in brief opening remarks that questions would be raised about who played what role in the incident.
Jack Pappas, appearing for Mr Loughhead, said the jury would ultimately find that his client, "dressed like a pirate on holidays", was trying to break up the altercation rather than further it.
He said even if there was "bad blood" between Mr Smith-Shields and the victim, the apparent rumours were "of sublime indifference" to Mr Loughhead.
The allegations levelled at Mr Loughhead were "just a furphy", Mr Pappas told the jury.
The jury will begin to hear evidence in the trial on Wednesday.