Three prisoners have been charged with murder over the fatal attack on Benton Parata at Christchurch Mens' Prison.
He was rushed to hospital last week but died on Monday.
Christchurch Police say three men aged 20, 21 and 36 are due to appear in the Christchurch District Court on Wednesday.
Detective Senior Sergeant Mark Worner says the police investigation team has been working closely with Corrections staff and the victim's family over the last week, and will continue to do so.
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