A former justice department boss has admitted youth detainees under his watch were subject to abuse.
The revelation came during an inquest into the first recorded West Australian juvenile death in a detention facility.
Cleveland Dodd was found unresponsive inside a cell in the trouble-plagued youth wing of a high-security adult prison in the early hours of October 12, 2023.
The 16-year-old was taken to hospital in a critical condition and died a week later, causing outrage and grief in the community.
Former Department of Justice director general Adam Tomison broke down in the witness box at the Perth inquest as he discussed criticism of the agency while he was in the top job.
"I was personally defensive because having spent 30 years in welfare I was now the guy hurting kids and it was extremely hard to deal with," he said while crying on Thursday.
"I wasn't expecting to break down.
"I wanted to do a good job ... but we were failing."
The court has been told some vulnerable detainees were held in solitary confinement at Banksia Hill Youth Detention Centre for up to 23 hours a day.
Dr Tomison agreed it was cruel, inhumane and degrading and a form of punishment.
He accepted it was institutional abuse of children that started in 2021 and in 2022 the "overwhelming majority" of detainees were victims.
When asked if the WA government was ultimately responsible, Dr Tomison said yes.
He said most staff members were empathetic to the detained youths and tried hard but the "process wasn't good".
The inquest was told Dr Tomison gave evidence at the disability royal commission in late 2022, saying prolonged confinement of detainees was not cruel punishment and the action was taken because it was the only option.
Under questioning from counsel assisting Anthony Crocker, he accepted he had got it wrong and it was a regretful stain on his reputation of his own making.
Cleveland fatally self-harmed at Unit 18 in Casuarina Prison.
It was established in July 2022 in response to the deteriorating situation in the prior 12 months at Banksia Hill.
The inquest has previously been told many detainees transferred to the unit were also locked in their cells for prolonged periods.
Dr Tomison, who stepped down from his job after Cleveland died but remains on the justice department payroll as a consultant, agreed the unit was opened in haste and poorly executed and the department should have started work on the second facility earlier.
He said he was surprised conditions at the unit deteriorated days after it opened despite being warned by senior corrections staff it would be difficult to properly care for detainees sent there, including giving them access to education and lawyers.
There are 60 boys and five girls in detention in WA, with nine of those boys held in Unit 18.
About 75 per cent of all detainees are Indigenous.
The coroner previously heard Cleveland made eight threats to self-harm and numerous requests for medical treatment and drinking water in the hours before he was discovered in Unit 18.
He had covered a CCTV camera in his cell with tissue paper, blocking the view of correctional staff monitoring him from a control room, but it wasn't uncovered until they were fighting to save his life.
The teen was taken to hospital but suffered a brain injury due to a lack of oxygen.
He died, surrounded by his family, on October 19.
The inquest continues.
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