The institutional racism and toxic culture at a troubled youth detention centre was so severe a consultant was afraid to raise it for fear of losing his job, the inquest into the death of Cleveland Dodd has been told.

Cleveland was found unresponsive inside a cell in Unit 18, a youth wing of the high-security adult facility Casuarina Prison, in the early hours of October 12, 2023.

The 16-year-old Yamatji boy was taken to hospital in a critical condition and died a week later, causing outrage and grief in the community.

Unit 18 was established in July 2022 after riots and damage to cells at Western Australia's main youth detention centre, Banksia Hill.

Cleveland's inquest on Thursday heard from respected veteran senior public servant Tim Marney, who was contracted to implement a therapeutic care model at Banksia Hill in the months before Cleveland died.

He told Coroner Philip Urquhart the racism and toxicity he observed was so serious he dared not raise it for fear of alienating the facility's management and inhibiting his ability to make change.

"By calling it out formally ... my tenure could be untenable," he said.

Mr Marney said the change he was seeking to make at Banksia Hill would have taken two to four years but he was asked not to return to the role after his initial six-month contract expired, despite not raising the issues.

He said achieving cultural change was a "very delicate exercise" and he could only "push" at a pace that the facility's leadership and management was prepared to accept.

"They weren't ready to receive that information, to hear that information or to change in that regard," he said.

Asked why he didn't raise the issue of racism immediately, Mr Marney said his primary focus at the time was the safety and wellbeing of detainees.

"There were other priorities that needed to be addressed, to seek to protect the young people, and those priorities took priority over that issue of institutional racism," he said.

He said while unacceptable, the racism had been tolerated for some time and no one's life was at risk because of it.

He said the facility's low staffing levels were his main priority because they were causing detainees to be locked in their cells for unacceptably long periods.

"Having enough staff to actually get kids out of cells," he said.

"(Staff) were leaving hand over fist ... joining and leaving within weeks because of toxic culture."

Mr Marney was WA's Under Treasurer from 2004 to 2014 and led the Mental Health Commission for five years. He also served on the board of Beyond Blue for nearly 12 years.

The inquest continues.

Aaron Bunch - AAP