A former inmate who is suing Corrections has made public a video of his brutal prison assault.
Benjamin Lightbody was smashed in the head by a prisoner with a pool ball in his fist in May 2013 while at the then Serco-run Mt Eden prison.
He suffered permanent brain damage and fought a long battle with Corrections to access the footage.
That battle led to the Privacy Commissioner ruling Corrections breached his rights, and that case was lodged with the Human Rights Review Tribunal.
The video, released by Mr Lightbody, shows him wandering about the yard, then felled by a single blow.
Warning, the video below contains violence
He lies on the ground without anyone coming to help, inmate or guard, and eventually staggers to his feet.
The inmate who delivered the blow was convicted of assault.
An inspector reported how the inmate lay near death in his cell for hours, and when guards eventually checked on him and could not rouse him, they went back to filing paperwork and eating sandwiches for 20 minutes before calling an ambulance.
The case against Corrections accuses the department of failing to keep him safe while in custody.