Mr Davis had drugs inside him when he went into the Otago Corrections Facility as a remand prisoner in February 2011.
Although Corrections staff knew that from an intercepted phone call, he was placed alone in an at-risk cell and did not receive medical help. He died in the cell two days later.
The inquest into his death heard he had a quantity of cannabis inside a plastic ziplock bag, and diazepam and dihydrocodeine pills in a pill bottle, which he had inserted inside himself.
Evidence showed that at least one or more times during his incarceration, Mr Davis had removed them and consumed the contents, before re-inserting them again.
He died overnight on February 13-14, 2011. His cause of death was determined as "the ingestion of lethal amounts of diazepam and dihydrocodeine".
Intelligence officers at the prison had intercepted two telephone calls made from an OCF phone to Mr Davis - a patched member of the Mongrel Mob gang - which indicated he would obtain drugs for gang associates in the prison and smuggle them in.
Two days later, on February 10, he went to Dunedin police to hand himself in for breaching his bail conditions on a charge of 'demanding with menaces', and was taken into police custody. He was later moved to the OCF, where manager Mike Fitzgerald asked that Mr Davis not "mix with Mongrel Mob members or other OCF prisoners".
Mr Davis was searched on arrival at OCF, no drugs were found. He was then placed in a 'dry cell' - one without a toilet or running water. He was also medically examined, and warned of the risks of internally concealing drugs, which he denied he was doing.
He was ordered to be checked on every 15 minutes, and over the next couple of days his condition deteriorating, with nurses determining was under the influence of drugs.
A plastic bag with the remnants of cannabis in it was also discovered in his cell.
An audit of some of the log book entries found a corrections officer did not physically go to view Mr Davis through the window as he was required to do on two occasions, and another recorded he was "asleep" on other occasions.
At around 4.56am on February 14, the officers believed there was something "not quite right" with Mr Davis.
Officers went into the cell together shortly after 5am, and discovered that he had died during the night.
Coroner Crerar said Mr Davis "took the risk of attempting to import drugs into OCF .... for his personal reasons".
"He knew that what he was doing was illegal.
"As soon as he realised OCF management knew of his plan, Jai Davis continued in his denial of concealing drugs; he did not give the drugs up as he ought and he has, instead, adopted the expedient of consuming the drugs in order to destroy or conceal evidence."
Because of this Mr Davis was "the author of his own misfortune", coroner Crerar said, but added that his gang associates who asked for the drugs, and others who helped him obtain them, shared a responsibility for his death.
"Jai Davis, himself, is however the person most responsible for the circumstances which led to his death."
In a statement released this afternoon, following the publication of the inquest findings, police said they had previously reviewed the original investigation and no new evidence had emerged.
"Following the conclusion of the inquest, police reviewed all of the evidence offered to assess whether [there was] any new evidence that would give rise to any criminal liability.
"The review, completed in February this year, found that the available evidence failed to meet the standards required by the Solicitor-General's prosecution guidelines and no charges against any individual should be laid in relation to the death of Jai Davis."
Police had also carried out an independent review, the statement said.
"Prior to the coroner's findings being released, police conducted its own review of the investigation, which was carried out by an officer from outside the district.
"That review identified similar issues to those released in today's findings, which in addition to the work already underway with Corrections at a national level to improve information sharing, have already been addressed by the district."
Since Mr Davis' death, police and Corrections had agreed to a process of information sharing, police said, where urgent information can be passed between Southern Police and the Otago Correctional Facility to "ensure thorough and timely communication occurs about such matters in the future".
"The Independent Police Conduct Authority has also advised Police that it is satisfied with the review," the statement said.
Mr Davis' family have fought for a prosecution in relation to his death, with his mother Victoria Davis telling the coroner's inquest in December that Department of Corrections staff had failed her son in their duty of care.
She told the court she was concerned that some prison staff had been "so indifferent to his wellbeing" that he had "unnecessarily died".
In his findings, Coroner Crerar criticised the lack of proper documentation and communication between agencies, saying his inquiry had been continuously "compromised" by such oversights.
It was an "embarrassment" for the agencies involved, he said, but "more importantly and significantly, the failure to record and share information could be seen as being a major contributor to the circumstances of the death of Jai Davis".
"Specifically Corrections intel knew the likely method of introduction of drugs to OCF by Jai Davis was by means of his concealing the drugs in his rectal cavity. Corrections intel also knew the drugs were likely to have included prescription pills.
"This, quite clear, information was scrambled within phrases 'internal concealment' and 'drugs' and may have, or could have, resulted in a loss of focus for those receiving Jai Davis at OCF and thereafter those who were responsible for his care."
One of the Corrections managers, Anne Matenga, admitted she had received no training in relation to prisoners who were suspected of concealing drugs, despite having worked at Corrections for more than 20 years. She also admitted to not knowing the term 'medical officer' meant a doctor.
This was "astonishing", Coroner Crerar said.
The evidence was that she was "poorly trained to perform her role and take her responsibilities, and she showed a poor appreciation of such responsibilities", he said.
The excitement by Corrections staff that they were receiving a prisoner who was smuggling drugs was like "buck fever", the coroner said, because of the rarity of such an event.
Some Corrections staff told the inquest it was the first interception of this nature in their many years of experience.
"Corrections management were so focused on the apprehension of Jai Davis that there was a general failure by Corrections management to consider other relevant implications -- particularly the safety and health of Jai Davis, during his admission," he said.
The decision to admit him in they way they did was "wrong", Coroner Crerar said.
"The focus ought to have been on the responsibility of Corrections for the health of Jai Davis."
The intelligence information about the kinds of drugs he was smuggling, and how, "ought to have been shared with the health centre manager and the nurses who were required to care for Jai Davis".
Dunedin police officers Sergeant Tony Ritchie and Detective Sergeant John Hedges had failed to open and read emails sent from Corrections intelligence about Mr Davis' plan, and analyst Rennae Flockton failed to record or pass on information, the coroner found, deeming it to be a "circumstance of the death" of Mr Davis.
"More than one person in police intel knew that Jai Davis was attempting to smuggle drugs into OCF, concealed internally. Why was that knowledge not recorded, disseminated and acted upon?," he said.
"It is surprising that, within several days of the relevant information being discussed, Jai Davis died. The recollections by the [police] witnesses were not recorded even then. It could have been expected that this event would focus the attention on all persons, even those with only a peripheral knowledge of the lead up to his death, to the need to make notes of their role(s)."
The delays caused by this lack of documentation and memory of the events had "significantly delayed" the inquest, he said.
"Professional police officers with intelligence and associated portfolios ought to have immediately, upon learning of the death, realised the importance of the information they had received and recorded this whilst it was still fresh in their minds.
"The existence of unopened emails, or emails which were not responded to in a timely manner, remains of concern."
An expert pathologist who examined the evidence said it strongly suggested Mr Davis was "at least deeply unconscious or already dead" somewhere between 10pm and midnight.
Dr Martin Sage estimated the time of death as between 11pm and 1am, and refuted suggestions he may have been alive after midnight.
He believed Mr Davis died after consuming a mixture of drugs, laying on the bed with the appearance of sleeping.
An observer from a distance would likely have been unable to distinguish sleeping, shallow breathing, unconsciousness, coma or death, he told the inquest. A possible contributory factor could have been the 'plasticy' and impervious mattress cover, which would have "offered a greater potential risk for obstructing the mouth and nose in an unconscious face-down person".
Dr Sage considered a recorded observation by a Corrections officer of a movement under his blanket at around 3.37am was "unlikely".
Paul Glue, professor of psychological medicine at the University of Otago and a consultant psychiatrist with the Southern District Health Board, was brought in as an expert witness for the inquest.
He said it may have been possible to save Mr Davis, even at the point of respiratory arrest, "if his precarious condition had been noticed".
If there had been routine checks, which included obtaining a verbal response every hour, the early stages of sedation and intoxication would likely have been picked up, and could have led to life-saving interventions, he said.
