A prison reform campaigner says coroners' courts need an urgent overhaul in order to reduce the number of deaths in custody.
Inquiries into the death of Jai Davis, 30, at Otago prison three years ago have passed to a coroner, now the police have decided not to lay charges.
Prison Reform Society president Peter Williams QC said the power to scrutinise jails when prisoners die rests with coroners courts.
But Mr Williams said the system itself is not generating the changes that are urgently needed.
He said prisoners' families are often not represented or involved properly at inquests, the Corrections Department has too much sway in the court, and coroners can suppress their findings from public view.
Courts Minister Chester Borrows is rejecting the criticism, saying Mr Williams is insulting coroners and needs to do his homework.
Mr Borrows says families can get legal aid for lawyers to represent them, coroners have all the power they need to run fair proceedings, and any suppressions they set are used to prevent copycat suicides.
He says a recent review of the Coroners Act has only proposed one change relating to deaths in custody, which would allow coroners not to hold a hearing when a death is clearly from natural causes.