One of the men on trial for the murder of Indigenous teenager Cassius Turvey has a "significantly stronger" manslaughter case against him, his lawyer says.
Cassius, a 15-year-old Noongar Yamatji boy, died in hospital 10 days after prosecutors say he was chased, knocked to the ground and "deliberately struck to the head" with a metal pole 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 he was "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 on the day.
Brearley denies he struck Cassius with a pole, claiming he only punched him after the teen knifed him and that Palmer struck the fatal blows, which he denies.
Palmer's lawyer, Christian Porter, on Monday told the jury during his closing submissions that Brearley had released "violent human energy" on Cassius, "fuelled by a dark part" of his character.
"Jack perceived a deep and insulting and humiliating wrong had been done to him personally," he said as he summarised a series of incidents that led to Cassius being fatally injured.
"Jack is so fuelled to find the target to take retribution to this perceived loss, that he catches the next teenager ... and this leads to a tragic, final, fatal situation.
"In a fit of sheer rage, Jack Brearley strikes the slowest teenager he had caught with a pole forcefully, ragefully, multiple times in the head and causes his death."
Mr Porter said there was no "serious evidence" to suggest Palmer had hit Cassius, but "there is an overwhelming amount of evidence ... that Jack Brearley struck the blows that caused death".
He said this was the sheer weight and high quality of the evidence, a recorded phone call to Gilmore's mother after Cassius was allegedly attacked, the forensic evidence and "that Jack Brearley was the only person with the capability for violence to do what was done".
Mr Porter conceded Palmer had aided Brearley, but he said there was insufficient evidence that his client knew about Brearley's alleged murderous intention.
"If there is a reasonable prospect that Brodie Palmer did not actually know Jack Brearley had that specific murderous intention ... then Brodie Palmer is not guilty, as a party to the murder," he said.
"But where the prosecution case is ... very significantly stronger is on manslaughter ... the common intention for an unlawful purpose would have an accidental death as a result, and I'm not going to argue against that proposition.
"Palmer was willing to get himself involved in something in the field that day, and that something was unlawful and you may well form that conclusion."
The trial continues.
