The coroner investigating the death of Indigenous teenager Cleveland Dodd has called for the youth detention unit he was held in to be closed and investigated, after finding that his death was caused by longstanding failures in the justice system.

Cleveland was found unresponsive inside a cell in the trouble-plagued Unit 18, a youth wing of the Casuarina high-security adult prison, south of Perth, in the early hours of 12 October 2023.

The 16-year-old was taken to hospital in a critical condition and died about a week later, becoming the first juvenile to die in a West Australian detention facility.

Coroner Phil Urquhart said the unit should be closed as a matter of urgency, and a special inquiry with more powers than the coroner’s court should be convened into how it came to be established.

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“No child in detention deserves to be treated in the way Cleveland and the other young people in Unit 18 were treated at the time he decided to end his life,” he said on Monday.

Prolonged periods of solitary confinement, isolation, intense boredom, eating meals alone, a lack of access to health, education and running water were the norm for Cleveland and the other detainees, he said.

“There were serious deficiencies in the way our young people were treated in detention,” Urquhart said.

“Cleveland’s death was not because of human error by those working on the floor … it was because of serious longstanding deficiencies in the system.”

The coroner made 15 adverse findings and 19 recommendations, including that a forum be established to explore whether the Department of Justice should have sole management over youth justice.

His findings included that Cleveland was subject to excessive solitary confinement in his cell and was not properly monitored while in there.

Cleveland’s damaged cell also had a hanging point which authorities were aware of but had not been repaired, and he had been denied access to counselling services despite requesting it on numerous occasions and making threats to self-harm.

During the inquest, the court heard youth justice was in a crisis at the time of Cleveland’s death.

Staff described the appalling conditions in which the young people were being detained and the chaotic operating environment at Unit 18, with some saying it was a “war zone”.

In the 12 days before he harmed himself, Cleveland spent between one and two hours out of his damaged and unfurnished cell each day.

Former Department of Justice director general Adam Tomison conceded it was “cruel, inhuman and degrading” treatment when cross-examined.

The inquest heard Cleveland self-harmed at about 1.35am and staff didn’t open his cell door to help him for more than 15 minutes, with paramedics arriving a further 15 minutes later.

The teen was partially revived and taken to hospital but suffered a brain injury because of a lack of oxygen.

He died surrounded by his family on 19 October 2023.

The WA government has previously said many improvements have been made in youth justice since Cleveland died and that a purpose-built facility to house detainees from Unit 18 will be completed within three years.

• Indigenous Australians can call 13YARN on 13 92 76 for information and crisis support; or call Lifeline on 13 11 14, Mensline on 1300 789 978 or Beyond Blue on 1300 22 4636