Western Australia's troubled juvenile prison has faced more unrest with detainees smashing cells following recent claims of human rights violations.
The head of WA's justice department told a budget estimates hearing on Monday there were about 100 cells out of action at the 250-capacity Banksia Hill detention centre.
Some had been extensively damaged with detainees smashing toilets, beds and communication devices and breaking apart the walls between cells.
WA's custodial services inspector in April revealed there were 24 suicide attempts at the prison between January and November last year, most involving boys who had formed a suicide pact while held in an intensive support unit.
Inspector Eamon Ryan found the human rights of four detainees had been breached across several days in November when they spent less than an hour outside their cells.
The McGowan government has since promised a $25 million spend on the facility which will largely fund infrastructure upgrades.
Department of Justice director-general Adam Tomison said older detainees had been coaching others on how to damage their cells.
He said there were children entering the facility with significant challenges including mental health issues, trauma and learning difficulties, some of whom had experienced better outcomes when connected with supports.
The cost of detaining a young person in WA is estimated at around $1352 per day.
Most detainees at Banksia Hill were on remand and not sentenced, Dr Tomison said. Around half were expected to return to detention.
As of April 30, Banksia Hill had 51 detainees aged 12 or younger, including one 10-year-old. The state has not committed to raising the age of criminal responsibility.
The department said there was no funding specifically allocated in this year's budget to install air-conditioning at Roebourne Prison, in the state's north, where the temperature exceeded 50C in January.
Officials said the department was investigating potential solutions but wouldn't be drawn on whether it would be resolved before summer.
The hearing was also told the backlog of cases before the state coroner's office had climbed to 1350 from 810 the previous year.
Almost 1000 of the cases were awaiting police, toxicology or pathology reports.
The bill to WA taxpayers for legal costs associated with defending various litigation launched by billionaire Clive Palmer exceeded $1.4 million, the deputy state solicitor told the hearing.
Mr Palmer sued Premier Mark McGowan for defamation in 2020, with the premier launching a counter-suit.
Federal Court Justice Michael Lee has reserved his judgment.