A coroner is strongly critical of security measures at prisons, saying the length of time it can take to unlock a cell door at night gives inmates little chance of survival in an emergency.
Coroner Katharine Greig has released a report into the death of Anna Selina Kingi, who died at the Auckland regional women's corrections facility in 2008.
Officers took 13 minutes to unlock Ms Kingi's cell to give her medical attention, by which time she was dead.
An internal investigation recommended the Prison Service review key security to ensure response times were quicker, but it rejected the suggestion.
Ms Greig recommends benchmark be set for opening cell doors that meets international best standard practice.
The prison service says it is trying to reduce the time it takes to unlock a cell door at night.
Prison officers are not allowed to carry keys at night in case they are attacked by prisoners.
However, assistant general manager Eric Fairbairn told Morning Report changes have been made so guards can get to a cell in 5½ minutes.