The family of Noongar man Roderick Narrier, who died in police custody in 2019, say he can be heard saying "I can't breathe" on audio played during the coronial inquest into his death.

The audio recording was played earlier this week during the inquest at the Coroner's Court of WA.

Mr Narrier was restrained after officers attended an alleged domestic violence incident at a residence in Kewdale, Perth, in the early hours of October 27, 2019.

At the time, WA Police said Mr Narrier "was behaving erratically and aggressively".

"Police managed to restrain him, and due to concerns surrounding his behaviour, (St John Ambulance) was then contacted to attend," the statement said.

Mr Narrier lost consciousness while being treated by ambulance officers, then stabilised after police and ambulance officers performed CPR.

He was taken to Royal Perth Hospital and died on October 30, 2019 after being in a coma for three days.

Mr Narrier's daughter, Leshanti Narrier, said outside court on Wednesday her father sounded calm in an audio recording, despite police claims he needed to be restrained in the prone position because of signs he was suffering excited delirium.

"I can tell my dad's voice from a mile away," she said.

"I know when my dad is angry and when he is calm, and he was calm.

"He said 'I can't breathe', he was just trying to tell them."

Ms Narrier was joined at the inquest by her mother, two brothers, aunt and paternal grandfather, Roderick Narrier Snr, who said his son's voice was not intense on the recording.

"There is no way he was fighting them," Mr Narrier Snr said.

"It has been really really hard to take, for the whole family.

"We hope this inquiry will see the police acknowledge that what they have done is wrong."

Mr Narrier said two police officers had already apologised to the family.

WA Police capability advisor Chris Markham told the court on Wednesday he would wait until the audio recording was enhanced before commenting on what was said.

Mr Narrier, 39, was handcuffed and pinned in the prone position by officers for a protracted period.

Mr Markham said a "miscommunication or misinterpretation" during the call for medical assistance may have caused the ambulance to arrive late to the scene.

"Ideally (the officer calling the ambulance) would have said it was a case of excited delirium and priority one," he said.

"That information would have assisted... it appears there was either a miscommunication or a misinterpretation."

Aboriginal Legal Service Civil Law human rights unit managing lawyer Alice Barter said training around excited delirium and asphyxia included slides urging officers to give all relevant information to attending paramedics.

Mr Markham confirmed while it is now part of police training, it was not at the time of Mr Narrier's death.

He said Mr Narrier was cuffed and restrained in the prone position while police waited for the ambulance to prevent him "harming himself or others" because verbally communicating with him was not de-escalating the situation, which he attributed to excited delirium.

Mr Markham made reference to statements made earlier in the inquest by police officers who said Mr Narrier had attempted to kick and bite them.

He agreed with barrister Anthony Crocker, who appeared remotely, that once a person in the prone position has been restrained it is good practice to get that person up and out of the prone position as safely and as quickly as possible.

Coroner Philip Urquhart is presiding over the inquiry, which began Monday and will conclude on Thursday.