The justice department needs urgent reform so it can better address the needs of young offenders, the prison watchdog has told an inquest for the first youth to die in West Australian custody.

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 about one week later, causing outrage and grief in the community.

Inspector of Custodial Services Eamon Ryan told the Perth inquest the WA justice department needs urgent well-resourced reform that adopts a trauma-informed care model for youth offenders.

"It involves a significant cultural change for all of the staff. It requires significant infrastructure change," he said.

"It's a fundamental reform of youth justice."

The department needed to stop detaining young people in "hard custodial infrastructure" and stop treating them like they were adult offenders, Mr Ryan said.

A trauma-informed model would address young people's unique needs, he said, which could involve employing welfare workers who build relationships with offenders and teach them life skills.

"It is working in other jurisdictions but getting from here to there is an enormous exercise and it's not for the faint-hearted," he said.

The court heard Mr Ryan had been advocating for the change for several years and the department has said it's committed to making change.

WA currently had 60 boys and five girls in detention, with nine of the boys in Unit 18 at Perth's Casuarina Prison where Cleveland had been held, the court was told.

About 75 per cent of detainees are Indigenous.

The inquest 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 also 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.

Cleveland was found at 1.49am and a code red alert issued two minutes later as staff tried to revive the teen.

Paramedics arrived at 2.06am but did not get access to Cleveland, who was found to be in cardiac arrest, for nine minutes.

The teen was partially revived and 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 on Wednesday, when the former Children's Court president Denis Reynolds is scheduled to give evidence.

Aaron Bunch - AAP