The four accused in the fatal bashing of 15-year-old Noongar Yamatji boy Cassius Turvey pleaded not guilty to all charges.

Jack Brearley 22, Aleesha Louise Gilmore 21, Mitchell Colin Forth 25, and Brodie Lee Palmer, 28, appeared in the Stirling Gardens Magistrates Court Wednesday morning via video link from various prisons.

They stand accused of attacking the school boy with a metal pole as he walked with friends in the eastern Perth suburb of Middle Swan on October 13, 2022.

Cassius spent five days in the hospital before being discharged, however he suffered a seizure and was rushed to hospital where he was placed in an induced coma; he died ten days later.

Cassius's older brother and his cousins made an appearance in court as well, they remained quiet as they watched the hearing unfold, with one of the relatives wearing a 'Justice for Cassius' shirt.

All four of the accused have been charged with multiple offences, from the murder of Cassius to the bodily harm of another Indigenous boy who was allegedly attacked by Brearley, Gilmore and Forth, and a fourth suspect; Ethan MacKenzie, aged 19.

Police said the incident was alleged to have happened four days before Cassius was fatally wounded, and the attack involved the boy being punched, kicked, and stabbed.

It was also alleged the boy was taken to a house and detained before being released.

All charges against Brearley, Forth and Palmer were read aloud to them, they each individually responded with 'not guilty'

Ms Gilmore pleaded not guilty to detaining the first victim four days before Cassius was allegedly attacked; she is not facing a charge of assaulting him.

They were remanded in custody until they make their first appearance in the Supreme Court in July.

Mr MacKenzie's case was adjourned for four weeks.