The additional three people arrested for the murder of Cassius Turvey appeared in Perth's Magistrates Court Friday morning and were remanded into custody.

Aleesha Louise Gilmore, Brodie Lee Palmer and Mitchell Colin Forth were charged with one count of murder each.

Palmer and Forth appeared in court to have their charges read to them.

Palmer's lawyer said as this was his first appearance no plea would be entered today however in due course they would be looking at entering a plea of "not guilty".

Both Palmer and Forth were remanded in custody until March 29 with bail to be considered.

Speaking outside the court, Cassius Turvey's mother Mechelle Turvey said this was not just a court date for her.

"It took me back to the day, it took me back to when Cassius described the incident and what they looked like," she said.

"In one way he told me a bit of that story so at least I had something under my belt to give me strength.

"This is just one step forward to justice for Cassius and it's also one step forward all of our healing, all of his family, as well."

Gilmore, the girlfriend of Jack Steven James Brearley who was the first to be charged with Turvey's murder, did not appear in court physically.

Gilmour spoke to the court via phone call where it was specified she had been in hospital and had yet to speak to a lawyer.

Gilmore was also remanded into custody until March 29, with bail not considered.

Brearley was arrested on October 13, 2022, and charged with unlawful wounding before the charge was later updated to murder.

Brearley appeared in the Supreme Court of Western Australia via video link from Casuarina Prison on Wednesday, January 18, and was remanded into custody until March 29.

It is alleged Brearley beat Cassius Turvey with a metal pole while the 15 year-old was walking home from school with his friends.

Palmer, Forth, Gilmour and Brearley will be remanded in custody until appearing before Stirling Gardens Magistrates Court on March 29.