The accused are Jack Brearley, 23, Mitchell Forth, 26, Aleesha Gilmore, 23, and Brodie Palmer, 29, all of whom have pleaded not guilty to the murder charge.

Ethan McKenzie, 21, is also implicated in the case, facing charges of assaulting another 15-year-old boy shortly before Cassius's attack.

Brearley's defense attorney claimed that Turvey attacked Brearley first, alleging that Turvey had a knife and had slashed Brearley's leg.

CCTV footage presented in court allegedly shows the group violently attacking the wrong boy, kicking him while he was on the ground and stabbing him.

After realizing they had assaulted the wrong person, the group allegedly returned him to Gilmore's house and gave him items as an apology.

The prosecution contended that Brearley attacked Turvey in retaliation for prior vandalism to his car, suggesting that Forth, Palmer, and Gilmore were complicit.

The trial, overseen by Chief Justice Peter Quinlan, is expected to last approximately 10 weeks and will include testimony from nearly 90 witnesses.

The trial of four individuals charged with the murder of 15-year-old Cassius Turvey has commenced in the Supreme Court of Western Australia.

He succumbed to his injuries and passed away in the hospital ten days later, prompting widespread public mourning and protests.

Prosecutor Ben Stanwix described Cassius' death as the culmination of a series of events unrelated to him, stemming from a rivalry between two teenage boys over a girl.

Cassius Turvey, a Noongar Yamatji boy, died after being struck in the head with a metal pole during an attack while walking home from school on October 13, 2022.

Tensions escalated leading up to Cassius' death, with Gilmore seeking out those involved in the rivalry just days before the incident.