The counsellor who pushed the police into a proper investigation of the death of Otago prisoner Jai Davis says Corrections staff will only change if some are prosecuted.
Mr Davis' inquest in Dunedin closed yesterday after eight days of evidence into how he died of a drug overdose in 2011.
Police had decided in April not to lay any charges, citing a lack of evidence.
They now said they would review all the evidence that was given by the 58 witnesses in the inquest to see what was new and if that changed the previous decision.
Prison counsellor Roger Brooking, who has pushed the investigation to this point with multiple complaints to the Independent Police Conduct Authority, said it was essential there be prosecutions.
"The only possible thing that will stop this happening again is if the police actually charges someone in the Corrections department, or maybe in the police... and that person goes to prison for failing to provide the necessaries of life".
Corrections taking this very seriously - chief custodial officer
The chief executive of the Department of Corrections Ray Smith declined to be interviewed about the case until the coroner made his findings.
But yesterday, the department's chief custodial officer Neil Beales told the coroner it was taking Mr Davis' death very seriously already.
Mr Beales said Corrections had gone through three reviews, and made a raft of changes as a result of Mr Davis' death, including specific procedures for prisoners internally concealing items, and communication procedures.
He said the two key corrections officers in the at-risk cell, Brent Thurlow and Fred Matenga, had been given written warnings.
Mr Beales very bluntly listed five critical failures at Otago prison.
He listed Mr Davis being sent to prison instead of straight to hospital, that no doctor was called, that he was segregated for security reasons, got a potty in his cell and was not observed properly or woken even once on his last night alive.
Mr Beales said his review was based on the cumulative act effect, also known as the swiss cheese model, in which all the system's holes lined up.
He said he could not say for sure if Mr Davis' life could have been saved.
Coroner adjourns for two months
Coroner David Crerar adjourned his inquest until 2 February next year, to allow the police time to decide again if they would lay any charges.
But Mr Crerar made it clear he was planning to dish out plenty of criticism.
He said he intended to make adverse comment about a list of people including: "Jai Davis, the associates of Jai Davis, the police and certain police officers, Corrections management, certain Corrections staff and certain health centre staff."
But Mr Crerar said after closed-door legal debate he would be careful to avoid prejudicing any prosecution or any defence over Mr Davis' death.
But Jai Davis' mother, Victoria Davis, had a blunt message too - she said that the guards should be fired and the nurses involved struck off.