A review of New Zealand's 18 prisons over a 12 month period showed thousands of inmates had experienced solitary confinement.
A report from the independent Office of the Inspectorate shows between 1 October 2020 and 20 September 2021, 5655 prisoners - or 29 percent of all prisoners held at that time - spent time in jail where they were segregated from social interactions.
Corrections said it did not underestimate the serious impact that segregation could have on the wellbeing of people in prison and their families, and said it was an area that needed to be addressed.
The lengthy report from the prison's watchdog showed thousands of at-risk prisoners had spent months or even years without contact with any other prisoners, and are now susceptible to long-lasting psychological effects, such as depression and paranoia.
"We have found that many of these prisoners would likely have experienced 'solitary confinement' as that term is defined in the Mandela Rules - more than 22 hours a day without 'meaningful human interaction'.
"We also found that such prisoners were managed in restrictive physical environments that provided limited sensory stimulation, and that the prisoners had little to do," it stated.
The report said solitary confinement was a legitimate tool of prison management.
"However, where a prisoner's opportunity for social interaction is limited for an extended period, there is a risk that the prisoner may experience insufficient meaningful human interaction to sustain their health and wellbeing.
"For this reason, the Mandela Rules prohibit solitary confinement in excess of 15 days."
The report said most prisoners in New Zealand prisons who were unable to be integrated would experience segregation for fewer than 15 days.
"However, we found there were a significant number of New Zealand prisoners who were unable to associate for longer periods, sometimes for a number of months and in some cases, in excess of a year."
It identified a range of psychological and physical effects from isolation including lethargy, impaired concentration, depression, anxiety, panic attacks, anger and irritability, perceptual distortion, and paranoia.
The Office of the Inspectorate chief inspector Janis Adair said this issue had long concerned her.
"The effects of segregation, solitary confinement, isolation, separation, and any other form of restrictive imprisonment, however this is described, demands the closest of scrutiny by oversight agencies."
The report also showed isolated prisoners were less likely to go through rehabilitation and education programmes.
"This makes it more challenging for prisoners to reintegrate into the community upon release and may make it more difficult for prisoners to demonstrate progress in any application for parole."
The report found the records kept by the Department of Corrections on the numbers of prisoners in solitary confinement were not clear enough.
"Given the impact of solitary confinement, accurate record-keeping for all those prisoners separated from the prison population is vital.
"The records kept by Corrections did not enable us to ascertain accurately how many prisoners were unable to associate, nor how many of those prisoners would have been by themselves in excess of 15 days."
Adair said the system needed to be redesigned.
"This report is a call to action to refresh, redesign and reimagine relevant policies, procedures and practices that operate in New Zealand's correctional landscape when managing individuals who need to be separated from the prison population."
In a long list of 59 recommendations, the report said Corrections should consider the quality of staff interactions with segregated prisoners.
"Corrections must do more to mitigate the extent of the isolation experienced by such prisoners, especially where that isolation is beyond 15 days.
"Prisoners who are segregated or placed in at-risk cells must be provided with opportunities for meaningful human interaction, with more to do and access to programmes and education to prepare them for release into the community."
It said facilities should be in contact with the inmate's family regularly, as well as improving their access to phone calls.
"Corrections should consider improving prisoners' access to telephones, so they have better engagement and connectedness to their social supports."
Adair said the concerns on the health and safety of prisoners in segregation were not limited to Aotearoa.
"This is not a challenge unique to New Zealand and segregation is, and ought properly to be, a concern for jurisdictions across the world.
"This report will be of interest domestically and also to international audiences, given New Zealand's obligations under the Convention against Torture and other Cruel, Inhuman or Degrading Treatment or Punishment."
'Working with the most challenging people in society' - Corrections
Through a statement, chief custodial officer Neil Beales said the Department of Corrections acknowledged the release of the report and accepted all recommendations made.
"We recognise the challenges involved in segregating prisoners and the impact on those who are segregated, and we are committed to ensuring we are targeting our efforts at those areas where we are at greatest risk of creating harm to those we choose to separate."
He said work had already started.
"Our Chief Adviser System Transformation will ensure that this work is undertaken collaboratively across Corrections and with the Office of the Inspectorate. Our prison directors have also committed to making short-term improvements and long-term gains."
Beales said over the next six months, Corrections would develop an interim assurance system for directed segregation orders, explore the adaptation of a dashboard to incorporate reporting on directed segregation orders, implement an interim escalation system and provide targeted support to custodial systems managers.
As stated in the report, removing a prisoner from the mainstream prison population and using segregation was a legitimate tool of prison management, he said.
"However, the chief inspector is right to conclude that the administration of segregation, including record-keeping and reporting and the existence of a robust assurance framework, alongside clinical involvement in how segregated and at-risk prisoners are managed are areas which we must address."
Beales said Corrections did not underestimate the serious impact that segregation could have on the wellbeing of people in prison and their families, which was exacerbated during Covid-19.
"While the choices we make have a significant impact on people in prison, every decision is made to prioritise their safety and wellbeing."
About the staffing challenges mentioned in the report, he said like many organisations and businesses around the country, Corrections had been facing on-going challenges related to staffing levels.
"We fully acknowledge the impact of this pressure, which is why we have been making a concerted effort to recruit, retain and train new staff.
"We have seen a strong increase in the number of job applications received for new Corrections officers, with over 5100 applications received since October 2022. During this time, we have had over 480 people recruited into frontline roles, with many more in the recruitment pipeline."
Beales said Corrections staff did an incredible job with respect and dedication when working with the most challenging people in society.
"They have obligations to public safety, the safety of their colleagues and the welfare of prisoners that can at times lead to very difficult choices with very limited options.
"However, it is right that we take the time now to recognise that we can, and should, always strive to do better," he said.
Amnesty International's campaigns director Lisa Woods said the poor record-keeping was unacceptable.
"This in itself is deeply concerning, that the government could not provide data to say whether or not prolonged confinement had occurred, and whether or not a human rights violation had occurred.
"This is important because if robust data is not being collected, we just don't know what is happening."