Cassius Turvey, a 15-year-old Noongar Yamatji boy, died in hospital 10 days after prosecutors say he was chased down, knocked to the ground and "deliberately struck to the head" in Perth's eastern suburbs on October 13, 2022.
Aleesha Louise Gilmore, 23, her then-boyfriend Jack Steven James Brearley, 24, and his mates, Brodie Lee Palmer, 29, and Mitchell Colin Forth, 26, are on trial in the West Australian Supreme Court for Cassius' murder.
Prosecutors say Brearley delivered the fatal blows while "hunting for kids" because somebody had smashed his car windows and allege Forth and Palmer aided him, and along with Gilmore, had a common purpose.
Brearley denies he struck Cassius with a pole, saying he only punched him after the teen knifed him and that Palmer struck the fatal blows, which he denies.
The trial that started in early-February has been told the alleged attack on Cassius in bushland was "the end point of a complex series of events that had absolutely nothing to do with him".
Prosecutor Ben Stanwix told the jury it was a "tit-for-tat escalation" and Brearley and Forth had later used a car as a weapon and chased down two boys, hitting one of them.
The following day, Gilmore's brothers warned that a group of teens could be coming to their family home, where Brearley also lived, looking for a fight.
Brearley and his co-accused allegedly armed themselves with metal poles before driving off to search for youths.
About the same time, Cassius and a group of about 20 fellow students caught a bus to the same area to watch a fight being talked about on social media.
Brearley, Forth and Palmer intercepted them near the field and in a series of incidents, Brearley was allegedly slashed with a knife and another boy was struck in the face with a metal pole.
Cassius and some of the other "terrified school kids" fled into nearby bushland.
"He was caught, knocked to the ground and deliberately struck to the head with a metal pole," Mr Stanwix said.
He was struck at least twice, the impact splitting his ear in half and causing bleeding in his brain, the prosecutor said.
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