The circumstances surrounding the inmate's death in custody in July 2013, one month after he was remanded in custody, will come under close scrutiny during a three-day inquest in the ACT Coroner's Court.

The man, 30, had a history of mental health problems and suicidal ideations, and was marked as a prisoner-at-risk by the courts.

Initially, he was placed in the Alexander Maconochie Centre's Crisis Support Unit, an area designed specifically to deal with unstable inmates.

But about three weeks later, the prison's High Risk Assessment Team decided he was eligible to be moved from the Crisis Support Unit if a bed needed to be freed up.

The prison was struggling to deal with the still ongoing overcrowding crisis, putting significant strain on the 10-bed Crisis Support Unit.

The day before his death, the inmate and a fellow prisoner were moved to the jail's health centre, in a ward adjoining the Crisis Support Unit.

The appropriateness of that ward for holding at-risk prisoners will be closely questioned during the inquest.

Counsel assisting Ken Archer said it was separated from the Crisis Support Unit by security doors and a corridor.

Significant areas of the ward, including the bathroom where the inmate died, could not be seen by people standing outside the door.

"The health wards were, although close to the CSU, quite isolated in reality," Mr Archer said.

Aspects of the cell design will also come under scrutiny, particularly fixtures in the bathroom, for whether they allowed prisoners to take their own lives.

The trainee psychiatrist who assessed the detainee on the day he died, Dr Andrea Rapmund, on Tuesday questioned the suitability of the design.

When asked why the fixture was inappropriate, she replied.

"Because of the potential risk to harm oneself."

The inmate was left on his own on the day of his death, after his companion was moved back to the Crisis Support Unit.

He was under 60-minute observations that, although completed by prison staff appropriately, may have been too predictable in their timing, the inquest heard.

The inquest also heard the World Health Organisation had suggested 60-minute observations were not effective in preventing suicide.

When he went to see Dr Rapmund before his death, he said he was "a bit down" but "alright I suppose".

He told her he wasn't suicidal at that moment but would tell AMC staff if he was. She assessed him as moderate-to-high risk of suicide in the longer term, but lower risk in the short term.

No fault is likely to be laid at the feet of the assessing doctor for not predicting the imminent death, the inquest heard.

Mr Archer said predictions of deaths in custody were "notoriously difficult".

"It is such an unusual event that its clinical prediction is difficult," he said.

A guard next observed the inmate in the outside courtyard at the health ward smoking at 6pm.

At 7pm, a nurse and custodial officer came to his door, but couldn't see him. They could see light coming from the ward's ensuite.

The pair weren't able to get inside the cell, and were delayed by minutes until another custodial officer helped them request the door be remotely unlocked.

The consequence of that short delay is unknown, because the inmate's exact time of death cannot be pinpointed.

They attempted to resuscitate him, but failed.

"No criticism would be levelled at those who very conscientiously tried to resuscitate [the inmate]," Mr Archer said.

"It was just part of the tragedy that their attempts were unsuccessful."

Mr Archer told Coroner Bernadette Boss that her role would be to make findings on the cause and manner of death.

He said it was also her role to examine any "causal nexus" between failings in care and the inmate's death.

Information sharing between mental health staff and corrections staff at the prison will also come under scrutiny.

Dr Rapmund said she had not known her patient had been moved to the health ward until he told her, did not know he was with another inmate, and did not know of the design differences in the cell compared to the Crisis Support Unit.

She said she was also never given access to minutes of meetings of the High Risk Assessment Team.

The death caused the "acceleration" of an internal review of the treatment of mentally ill detainees in the AMC.

It also sparked an internal and police investigation, details of which will feature in the current inquest.

The bathroom fixtures have since been changed.

The inquest continues on Wednesday.

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