WA Police announced a fifth man had been charged on Monday.
The 23-year-old was also charged with murder and will appear in Armadale Magistrates Court on Tuesday.
The news comes after the Department of Justice revealed a 65-year-old male prisoner was in a critical condition after he was found with head injuries inside Hakea jail earlier this month.
The man was found in a recreation compound at the jail.
«The remaining prisoners in the compound were safely returned to their cells, while
the site was secured,» the department said.
The man was taken by ambulance to Fiona Stanley Hospital where he was placed in
an induced coma.
He has since been transferred to Royal Perth Hospital for emergency
surgery and he remains in the State Trauma Unit in a critical but stable condition.
«The Department of Justice does not comment on individual cases but at risk prisoners are closely monitored for the continuing safety and security of prison officers and staff, prisoners and facilities,» the department said.
«The Department of Justice has begun an inquiry into the incident while a WA Police investigation is under way.»