UPDATED 3.34pm: The man who complained to the police watchdog about the investigation into prisoner Jai Davis' death believes nearly two dozen people could have been charged in relation to his passing.

Mr Davis died in 2011 at the Otago Correctional Facility as a result of a suspected drug overdose.

Late last year an inquest heard how he concealed drugs before going into the facility and died a few days after arriving.

The review found the evidence failed to meet the standards required.

Alcohol and drug counsellor, Roger Brooking is stunned by the decision not to prosecute.

"There is so much evidence pointing to negligence and breaches of corrections protocol in the death of Mr Davis that I cannot believe the police are not going to prosecute somebody."

Roger Brooking says evidence points to everybody who dealt with Mr Davis knowing he was concealing drugs, yet no one called a doctor.

But as Jai Davis' mother, Victoria, explains - she was rung this morning by Inspector Steve McGregor to be told they won't be laying charges.

"He said that Corrections had admitted that they put Jai under the wrong section, and that there was a systemic breakdown at the time."

Ms Davis says this isn't the end of her fight for justice.

"I will be looking with my lawyer at whether civil action is where we go from here. There needs to be accountability."

David Crerar is set to release his findings in the coming weeks.

The Department of Corrections says it's formerly apologised to the mother of Jai Davis and is now awaiting the coroner's findings into his death.

Police have announced today they won't be laying any charges over the death, following a review of the case.

Corrections CEO Ray Smith says he acknowledges the police decision.

He says since the death four years ago, Corrections has implemented all the recommendations arising from its reviews.

Ray Smith says in their apology they've admitted some of the care of Mr Davis fell below the standards expected.

90 deaths in custody

A proponent for penal reform believes the death of prisoner Jai Davis shows a lack of accountability from the Department of Corrections.

Drug and alcohol counsellor, Roger Brooking, says 90 prisoners have died an unnatural death while behind bars over the last decade.

"And not one Corrections employee has ever been prosecuted over the death of a prisoner and I just think that's unbelievable."