A former Mt Eden inmate is suing the private prison operator Serco for half a million dollars.
Alex Littleton said he was beaten up by four prisoners and dropped off a balcony while in jail in 2015.
He is suing Serco for $500,000, alleging gross negligence on their part.
There was an administrative hearing in the High Court in Auckland today, with the company attempting to ensure security for costs.
In 2015, Mr Littleton said he had crawled to a guard window for help during the assault, but received no response until the attackers began to stomp on his head.
And he said he had not been given proper medical care when he was released back to prison there.
Serco ran Mt Eden for four years from 2011.
But its management was blighted by allegations of fight clubs, understaffing and poor supervision.
The government stepped in to take over running Mt Eden in 2015 after a series of scandals.
Serco was still involved in some administration until March when Corrections fully took over.