One of the group accused of murdering Indigenous teenager Cassius Turvey in October 2022 has applied for a separate trial on charges of detaining and assaulting another teenager days before the alleged attack on Turvey.

Jack Brearley, 23, is one of four people – Aleesha Gilmore, Mitchell Forth, Brodie Palmer and Ethan McKenzie allegedly involved in the assault of Turvey, 15, as he walked with friends in the eastern Perth suburb of Middle Swan on October 12, 2022.

All four appeared at the Supreme Court in Perth on Thursday ahead of a trial, set for in February next year.

The four are also accused of assaulting another teenager a 13-year-old boy at the incident.

Cassius Turvey died after an alleged attack in Perth in October 2022.

Mr Brearley, Ms Gilmore and Mr Palmer, are also facing charges over an alleged kidnapping and assault of another 15-year-old boy days earlier, on October 9, 2022.

All four, who are in custody and faced the court via video link, pleaded not guilty to the charges.

The application to split the charges and the trial will be a formally heard at a hearing in August.

Cassius died on October 23, 10 days after the alleged attack.