The WA Coroner has again urged WA Police to rein in their use of the dangerous prone position hold when restraining people experiencing mental health crises, this time in the findings on the death in custody of Noongar man Roderick Narrier.

Mr Narrier died on October 30, 2019 from cardiac arrest after being restrained by police in the prone position for 22 minutes during a mental crisis.

Coroner Philip Urquhart found that while positional asphyxia was not a factor in Mr Narrier's death, he said he "remains concerned (and) troubled" WA Police had not sufficiently updated training manuals since the death of Cherdeena Wynne, a 26-year-old Noongar Yamatji woman who stopped breathing while she was being detained by WA Police in April 2019.

It is the second time in six months the WA Coroner has called on WA Police to reduce the use of the prone position hold.

In April 2022 coronial findings into the death of Ms Wynne said police training should be updated to minimise the risk of causing death by positional asphyxia in the person being restrained.

Mr Roderick Narrier. Photo supplied by his family.

Mr Urquhart's findings were critical of the WA Police Internal Affairs Unit for failing to assign the matter of Mr Narrier's death to a senior investigator and failing to adequately investigate audio recordings of the incident.

The Coroner was also concerned the Internal Affairs Unit failed to interview the four police officers involved in the incident.

Mr Narrier's sister Monica Narrier said there was no justice for her brother's death.

"I believe everything went against his will at the time of his death," she said.

"Put yourself in our shoes, how would you feel? My brother Roderick Narrier was a good man, we were very close."

Ms Narrier said her brother was a healthy man who should not have died that day.

The family believes there were serious failings in both the police response to Mr Narrier's mental health crisis and in their investigation of his death.

"We believe that the police and ambulance all failed their duty to protect and serve," Ms Narrier said.

Legal advocates for the family are disappointed the coroner failed to accept the family's evidence they could hear Mr Narrier saying "I can't breathe" in an audio recording of the incident.

The National Justice Project said despite the coroner's previous warnings against excessive use of the prone position, the findings did not acknowledge the role use of the prone position may have played in Mr Narrier's death.

National Justice Project solicitor Karina Hawtrey said to prevent more deaths, coronial inquests must investigate systemic issues that may have contributed to a person's death - such as the role of police as first responders to mental health crises - not just the immediate causes of death.

"A person experiencing a mental health crisis should be attended to with urgent medical care, not handcuffs," she said.

"The Coroner has placed the responsibility for Mr Narrier's death onto the deceased man himself."

A spokesperson for WA Police said the Coroner found that the officers involved in the restraint of Mr Narrier acted appropriately in their conduct.

Asked about the Internal Affairs Unit investigation and if police training materials would be changed, the spokesperson said WA Police will review the findings made by the Coroner.

The WA Police Minister's office has been contacted for comment.