Martin Fulton, 18, was captured on mobile phone footage kicking 60-year-old Michael Rigby as he tried to restrain another male at the Good Life Festival in February.
Fulton pleaded guilty to the assault, along with a charge of trespass for jumping over the fence to gain access to the underage event.
His lawyer told the Perth Magistrates Court, Fulton had turned 18 just days before the festival, and was therefore officially too old to join his friends.
The court was told Fulton was at the festival for about an hour when he saw Mr Rigby with his forearm over the throat of another male on the ground, which triggered him to kick the guard once before fleeing.
The victim lost consciousness for a short time and suffered swelling and bruising.
Fulton’s lawyer described his client’s actions as “deplorable and disgraceful” but said they were not senseless or random.
He told the court the case had attracted “significant and sustained” media coverage and Fulton and his family had been targeted and threatened by members of the public.
Chief Magistrate Steven Heath sentenced Fulton to an eight-month immediate prison term, describing the offence as a “random and cowardly attack”.
He also ordered that upon his release, Fulton be subject to a two-year court order, with conditions including he not attend any events where there will be more than 100 people, promote any events on social media, or go festivals of any kind.
Victim hopes jail term acts as warning to others
Mr Rigby said the result was a “good outcome”.
“[I’m] very happy with the justice system,” he said.
Mr Rigby hoped the case would serve as a warning to others.
His friend Michael Riley was also pleased with the result.
“Eight months plus a two-year prohibited behaviour order, that’s pretty much a three-year sentence,” he said.
However, Mr Riley was concerned Fulton had been able to travel overseas during the case, causing delays in preparing a pre-sentence report.
“We’ve sent an email to the Attorney-General. We still want answers as to why he was allowed to leave the country … a lot of questions still need to be answered,” he said.
Both Mr Rigby and Mr Riley rejected claims Fulton was remorseful about his actions.