A coroner has dismissed a bid by one of WA's highest ranking justice bosses to remove himself from an inquest into the state's first death in youth detention.

WARNING: This story discusses incidents of self-harm and contains the name and image of an Indigenous person who has died.

Cleveland Dodd, 16, died in hospital almost a year ago after self-harming inside his cell at a juvenile detention unit inside a maximum-security adult prison.

Coroner Philip Urquhart has been overseeing the inquest since the day after Cleveland's death, when he visited Unit 18 with counsel assisting Anthony Crocker.

The inquest has sat for about 27 days since then and had been preparing to hear from a final group of witnesses this week, until Deputy Corrective Services Commissioner Christine Ginbey last week sought to have Coroner Urquhart removed from the case.

It was also revealed on Monday that there is now likely to be a fourth round of hearings.

Ms Ginbey's lawyer, Grant Donaldson SC, last week argued Coroner Urquhart and his Counsel Assisting, Anthony Crocker, had demonstrated "apprehended bias" on 18 occasions.

He described those occasions as including Ms Ginbey being berated and bullied while on the stand, and that she was treated differently to other witnesses.

Coroner Urquhart spent about three hours handing down his decision and addressing each of the 18 claims, dismissing all of them but accepting minor errors or oversights in relation to two.

In explaining why he had rejected the application, Coroner Urquhart said an apprehension of bias — which means a "fair-minded lay observer" might reasonably apprehend he may not bring an impartial mind to the issues — needed to be "firmly established", which was a "high bar that reflects the gravity of the application" but which Ms Ginbey’s application fell “well short” of meeting.

"I am satisfied that the attempt to portray those 18 matters … as factors which it is said might lead a judge to resolve the question other than on its legal and factual merits does not represent the full and proper context of what occurred," he said.

"None of the 18 matters, either individually or when considered cumulatively, discharges the burden which Ms Ginbey bears in this application."

Coroner 'running on empty'

A visibly tired Coroner Urquhart, who at one point said he was “running on empty”, rejected the assertion Mr Crocker had bullied Ms Ginbey while on the stand, saying the questioning was done in a “calm and logical manner, affording Ms Ginbey every opportunity to explain herself”.

He acknowledged some witnesses had been treated differently, giving the example of former director general Adam Tomison being given the opportunity to apologise to Cleveland’s family during his evidence.

"In those circumstances, it is not surprising she was questioned more firmly at times than those questioning of other senior executive witnesses.

Ms Ginbey previously told the inquest a document her boss said contained "a series of grievous lies" instead "described intent", and that a comment comparing services at Unit 18 with those at the main detention centre was "open to different interpretation".

Coroner Urquhart said he was confident a hypothetical observer would have been satisfied a "forensically passive approach" in questioning Ms Ginbey's evidence was not the only way the court could approach the issues it was considering.

He did, however, accept to minor points on the allegations raised – one relating to an “error” in the way Ms Ginbey was questioned over a key document being provided late, and the other being an “oversight” in relation to a witness not being re-questioned, which he put down to Mr Crocker’s workload.

He said neither rose to the level of demonstrating apprehended bias.

Ms Ginbey's application was last week described as a "remarkable attack on this court, both your Honour and counsel assisting" by Steven Penglis SC, who is representing Cleveland's mother Nadene at the inquest and opposed Ms Ginbey’s application along with the Aboriginal Legal Service.

Ms Dodd and Department of Justice staff were among those seated in the public gallery at Monday's hearing.

Advocate Megan Krakouer, who has been supporting Cleveland’s family, welcomed the decision.

“For another coroner to come in, it would have been an absolutely ginormous task,” she said.

“It would have set back the unaddressed trauma that the families currently have because they don’t know what’s happened with Cleveland and they want to know.”

Fourth round of hearings likely

It had been expected the final group of witnesses would appear this week but at the conclusion of Monday's hearing Coroner Urquhart said a fourth round would be necessary to allow the Department of Justice to respond to a new report which had been prepared.

He invited lawyers involved in the case to also make applications for other witnesses to be called, which could include former corrective services minister Bill Johnston, who approved opening the problematic unit.

In August he defended that decision, despite what had emerged during the inquest saying he acted in good faith to protect staff working in youth detention.