Sydney teenager Eden Delir was socialising at a friend's Halloween party when a group of aggressive gatecrashers recognised him as someone they had once robbed.
"That's the guy that snitched," one of the six young men said, referring to his police report.
A Sydney court has heard that the men began verbally abusing the 17-year-old, calling him "fatty" before beating him up in the front yard of the Bossley Park house in Sydney's west on October 30, 2010.
They allegedly punched him to the ground, kicked him in the head and smashed a bottle over his head.
The 17-year-old ran for his life.
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A Sydney man, who cannot be named because he was under 18 at the time, is on trial for Eden's murder after pleading not guilty.
Crown prosecutor Paul Leask told the jury in the Supreme Court trial that the attack was linked to Eden reporting the robbery to police.
"Eden had the temerity to complain to the police about the violence he received during the robbery." Mr Leask said on Monday.
"One of them must have recognised him.
"It's the crown case that Eden then suffered a ferocious attack.
"He was hit to the head and kicked to the head in circumstances where he didn't have a chance - six against one.
"It is alleged that this accused had a bottle and he smashed it over the head of the victim."
Eden made one last call to a friend who lived nearby, saying he had just been bashed and asking to be picked up, the court heard.
His friend never found him because he ended up collapsed in the yard of nearby house.
The resident of the house initially only heard him moan from his injuries and thought he was a distressed dog until finding the young man lying on the ground covered in blood, the court heard.
Eden never regained consciousness and died in hospital a week later.
"He died because he bled inside his head," Mr Leask told the jury.
The court heard that a number of items were found by the police in a car that was linked to the accused.
They included Eden's hat with the accused's blood on it and a bag with items belonging to the accused.
Eden's mother Dorothy Delir spent much of the first day of the trial sobbing softly in the gallery of the court.
The trial before Justice Peter Hall is set down for four weeks.
