A jury has been told a man who died in custody would have likely survived if he had received the medical treatment he needed.
Three Taranaki police officers are on trial charged with the manslaughter of Allen Ball.
Ball died on the concrete floor of the Hāwera Police Station in the early hours of 1 June, 2019.
He died of a self-inflicted overdose of codeine, tramadol and alcohol.
The Crown argues the officers failed in their duty of care for him, and are culpable for his death.
The defence team says the officers, who have name suppression, made mistakes but that did not make them criminals.
They have pleaded not guilty.
Today the jury heard from emergency medicine specialist Dr Paul Quigley, who said the drug and alcohol cocktail Ball had taken was a lethal mix.
"That combination would mean that he'd steadily get into an unconscious state as we saw [in the CCTV footage].
"His breathing rate would drop and he would slowly build up a poisonous gas that we all make called carbon dioxide.
"And as that rate rises that would also cause coma until you reach the point where you basically go into what's called respiratory arrest and stop breathing."
At that point first responders would have four minutes to give a patient oxygen to save their life.
Dr Quigley said if an ambulance had been called its crew would have spotted Ball had opiates in his system.
"A combination of decreased breathing rate plus very very small pupils means opiate poisoning and they would have the ability to give a drug called Naloxone, which reverses opiates and also up his breathing and may even wake him somewhat."
Crown prosecutor Cherie Clarke asked Dr Quigley how long that would take to work.
"It's on the end of a needle. It's basically as you give it."
Dr Quigley, who this afternoon had yet to be cross examined, was also asked about Ball's level of consciousness on CCTV footage of the incident.
He said Ball appeared "deeply unconscious" and unresponsive from the time he arrived at the Hāwera Police Station, comments that mirrored those of an earlier expert witness.
Former paramedic André Slierendrecht, who is the managing director of a police first aid training provider, observed Ball made no deliberate movements and was unresponsive in the video.
Under cross-examination from Susan Hughes, Slierendrecht was asked if the officers had any reason believe that he was not simply drunk as they believed?
"I think the primary indicator is that he got in the car and he couldn't get out," he replied.
Hughes pushed further, asking: "But up to that point they had no reason to think ...?"
At which point Slierendrecht conceded: "Absolutely not. I agree."
Under re-examination Clarke pointed out Ball had fallen asleep in the car and had to be carried into the station by six people.
She asked Slierendrecht if that sounded like a drunk sleeping it off?
"It's totally beyond sleeping and I would question that if that occurred in the car this is when a major decision should've been made - that medical help sought."
Clarke asked if Ball's state was consistent with sleeping or unconsciousness.
"Unconsciousness," he replied.
The Crown was due to end its case today.