Experts are calling for improved screening of prison populations, with a major study showing the disturbing number of traumatic brain injuries suffered by inmates.
The 2017 study of over a thousand inmates found two thirds of them had suffered at least one traumatic brain injury.
The prevalence of brain injuries among prisoners presents a unique challenge to the justice system, as the injuries have been linked to an increased risk of offending.
Former inmate Ben Lightbody still suffers the effects of a massive brain injury he suffered in 2013, when he was viciously assaulted by another prisoner holding a pool ball.
He says his brain is still missing 31 percent of its capacity.
He’s had five surgeries and a cranial implant now holds the pieces of his skull together..
After his highly publicised attack, Mr Lightbody says he received many messages from other prisoners sharing their stories of brain injuries in prison, whether they were sustained behind bars or before their arrest.
He says prison life can be "worse than hell" for inmates with brain injuries, who are often beaten or extorted by other inmates.
Psychologist Alice Theadom helped lead the 2017 prison study and spoke with Newshub Nation about her findings.
"We found 64 percent [of the prisoners] had experienced at least one injury. In the general population for males of equivalent age it's around 14 percent. So it is about three four times higher."
She says assaults were a major cause of the injuries, but many inmates had suffered more than one traumatic brain injury during their childhoods and adult lives.
Arana Pearson from Whakatōhea Iwi Social and Health Services helps people with brain injuries who have come into contact with the justice system, and says their injuries contribute to a cycle of homelessness.
"I think that any human being deserves a right to a home and particularly people with acquired brain injury," he says.
"Once you are in that homelessness cycle the only home they really see is prison, which becomes a relief for them because there's food there's a bed to sleep in."
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