Coroner Robert Cook also recommended on Wednesday that the jail consider introducing compulsory exercise programs, and remain vigilant in stopping illegal drugs from getting into the prison.

Steven Freeman's admission to the methadone program, as well as his tolerance to the drug and the treatment and care afforded to him in the days afterwards were topics scrutinised at the inquest into his death in the ACT Coroner's Court over several weeks last year.

In Wednesday's findings, the coroner "recognise[d] deficiencies and inconsistencies" within the Alexander Maconochie Centre's methadone program. But he was unable to conclude that those deficiencies and inconsistencies affected the quality of care, treatment and supervision afforded to the 25-year-old Indigenous man, to the extent it contributed to his death on May 27, 2016.

The inquest heard that a third of inmates are on methadone.

The inquest also heard that Mr Freeman died two days after he was first started on the drug. He had his first 30mg dose on May 25 and his second on May 26. The cause of Mr Freeman's death on May 27 was aspiration pneumonia secondary to methadone toxicity.

Because while Mr Freeman held himself out to be a user of heroin, there was little evidence he was a heavy opioid user, and, the coroner found, it was highly likely he was opioid naive when he was prescribed methadone in May 2016. The toxicity of a certain dose of the drug can differ, depending on a person's tolerance.

Mr Freeman had been caught with a prescription opioid before, and the inquest got an insight into prison drug taking practices when it heard Mr Freeman had reportedly taken "drinks" of other prisoner's oral methadone, after it had been regurgitated and mixed with orange juice. The inquest heard he had expressed an interest in going on methadone, to "do his time easy".

When Mr Freeman met with the prison doctor he said he had recently smoked heroin and was considering injecting the drug, and incurring drug debts along the way, the doctor Luke Streitberg said.

But despite the earlier incidents, there was no official record of his dependence on opioids, and his family were adamant Mr Freeman, though a drug user, was never addicted to heroin.

Mr Cook found the doctor had accepted Mr Freeman's claims he was opioid dependent, notwithstanding the absence of any independent evidence of those claims. But Mr Cook said the doctor's actions did not affect the quality of care, treatment or supervision of Mr Freeman to the extent it had contributed to Mr Freeman's death.

He urged the government to consider implementing the national opioid guidelines to replace the existing guidelines and "incorporating random urinalysis or blood tests where there is no objective medical history of opioid dependence".

He also said the morning welfare check on Mr Freeman did not meet the jail procedures, though that was not a contributing factor to his cause of death. He recommended a review of the existing practices.

He recommended too that the prison consider a compulsory exercise program for inmates, and that the lack of such a program so far was "startling". He said it was concerning that a prisoner could remain in bed or in their cell from early one evening until 11am the next morning, as the court heard Mr Freeman was.

Outside court, Mr Freeman's mother was in tears when she spoke to the waiting media and said the system needed to change.

"I don't want it ever happen to another mother, no matter what culture they are," Narelle King said. "I'm just disappointed I lost my son and I'll never get him back."

Head of the Winnunga Aboriginal Health Service, Julie Tongs, said the Freeman family had been let down because of the government's failure to follow national opioid treatment guidelines in the jail.

"There has been a commitment and there are recommendations, and we have moved along as far as the Moss inquiry goes, but we've still got a long way to go and it's not going to happen overnight," she said.

Coroner Robert Cook's recommendations: