Three men have been charged with murder following the death of a prisoner critically injured in an assault at Christchurch Men's Prison.
Benton Marni Parata was placed on life support when he arrived at Christchurch Hospital on Wednesday 25 March.
The 44-year-old never regained consciousness and died on Monday.
Three men - aged 20, 21 and 36 - are due to appear in the Christchurch District Court next Wednesday.
Detective Senior Sergeant Mark Worner said police had been working closely with Department of Corrections staff and the victim's family over the last nine days and would continue to do so.
Ten police staff are continuing to work on the investigation.
Mr Worner said the victim's family were understandably very upset and have asked for privacy so they can grieve as a family.