Concerns are emerging those sent to prison for "strike" offences are ending their sentences having completed no correctional programmes, raising the risk they pose to the public and also the chance they will be returned to prison.
Inmates serving second and third strikes offences are obliged under the law to serve the full length of their sentence, removing any incentive to seek early parole by taking courses intended to cut reoffending.
It has also been stated the nature of the "three strikes" sentences means offenders are technically barred from courses designed to help them reintegrate with the community - a key factor in stopping inmates from committing crime when released.
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The Three Strikes law was passed in 2010 after a deal between the National Party and Act Party.
The concerns emerge ahead of a three-day criminal justice summit being held by the Government in Wellington next week as a major step in Minister of Justice Andrew Little's plan to reform the criminal justice system.
Lawyer Judith Fyfe, who specialises in parole cases, said those in prison needed access to reintegration programmes - such as release-to-work schemes - to reduce the chance of reoffending on release.
But she said those on second and third strike offences could not undertake reintegration courses because the nature of the sentence meant they were not eligible for parole.
Little - who tried and failed to repeal the law this year - said the Three Strikes regime meant offenders would not address the issues which would help keep them out of prison, such as improving literacy and learning skills.
"They've got no incentive to do that and why would they because nothing they do is going to make a difference to the time they are there."
Victim advocate Ruth Money, who is also on Little's Safe and Effective Justice Advisory Group, said it was negligent to not have a mechanism by which the most serious criminals could seek rehabilitation or reintegration.
Money, who was a member of the Sensible Sentencing Trust at the time it backed the law, said: "Those second-strikers - if you look at their history - we should be pushing them through rehabilitation."
Former National MP Chester Borrows said: "That was one of the reasons I never liked the Three Strikes legislation.
"It was a political animal. It didn't come out of any sound thinking on behalf of the incoming National Government. It came out of a deal where they needed the Act Party to get into government as confidence and supply partners."
Justice campaigner and gang culture expert Denis O'Reilly said those sentenced on strike offences would be a danger to staff and other inmates while in prison if they were not engaged in processes that helped them understand why they were there.
"They're dangerous when they're in there and they're definitely dangerous when they come out. The thing is to acquaint people with their predicament.
"If you never realise you have a problem, you're not going to do anything about it."
National Party leader Simon Bridges said he believed the Three Strikes law was fit for purpose.
He said "statistical tricks and devices" had been used to "pooh-pooh" the effectiveness of the law but he believed figures showed it deterred people from reoffending.
Ministry of Justice statistics have shown a drop in the number of people who have offended after a first strike, when compared against the previous five years, but have said it is not evidence the law works because of other changes in the criminal justice system.
Bridges said: "The strike system is about deterring those individuals from going on to further crime and I would argue any day of the week that works."
A major report into the criminal justice system by the Prime Minister's former chief science adviser Sir Peter Gluckman found there was no evidence of a deterrent value.
Bridges said, "Peter Gluckman can do a literature review [and] he can have all manner of academics with their variety of views" but he had studied the matter himself.
"People do less crime if they have a fear they will be caught and that the penalty will be stiff enough."
The Parole Board holds information on the issue but is refusing to release it, or to make any comment and has refused to say why it is keeping silent on the issue.
Corrections chief custodial officer Neil Beales said prisoners could not be forced to take part in prison programmes but effort was made to encourage involvement.
He said those on second or third strike offences often had a history of using violence to solve problems, were fixed in a gang lifestyle or had mental health or addiction issues.
"These can all be barriers to them addressing the causes of their offending and developing new skills and strategies to live crime free in the community."
A Corrections spokesman said: "Given prisoners with both second and third strikes do not have the possibility of release on parole, they do not qualify for temporary releases or reintegration activities outside prison."
Criminal justice summit
• Corrections Minister Kelvin Davis will speak on the over-representation of Maori in prison.
• Corrections is outlining a wish-list of programmes it could introduce.
• Children's Commissioner Judge Andrew Becroft gives a vision for criminal justice that addresses drivers of crime at the earliest age.
• Justice Minister Andrew Little on how the failures of the past can improve the future.
• Short-term prison initiatives that deliver change will be presented.