Shorter prison sentences and open jails are among changes which would improve our criminal justice system, according to one of those believed to be in the running to take over as Chief Justice.
Justice Stephen Kos - the president of the Court of Appeal - has spoken of the need to reform New Zealand's criminal justice system as the number of people in prison has soared.
"Those who think the justice system cannot sensibly be improved, are not thinking," he told the Legal Research Foundation's annual meeting in Auckland.
Kos sketched out ideas for reform, saying the views expressed were his personal opinions while offering evidence to support his position.
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"Prisons are good places for bad people. They are places in which the dangerous should be kept."
But he said prisons were not for those who were mentally unwell, as 60 per cent of those sentenced to prison were shown to be, or those with "decent rehabilitation prospects".
Those with little criminal history who posed no danger to society "should spend as little time there" as necessary to "denounce their offending".
Kos' speech comes as Chief Justice Dame Sian Elias prepares to retire at the mandatory age of 70. Kos and Justice Helen Winkelmann are considered in legal circles to be front-runners for the role.
The speech by Kos follows a High Court judge who called for lawyers to provide evidence longer prison sentences actually put people off committing crime.
In that hearing, there was no evidence presented by the Crown to support deterrence while defence lawyers were able to produce research exists showing it didn't work.
Kos also targeted the length of prison sentences in offering three immediate paths to criminal justice reform.
He said it would be improved by shorter sentences, different types of sentences and new types of prisons.
On the length of sentences, Kos said he had seen no "convincing evidence" either individuals sent to prison or the general public were put off crime by the length of time they would serve if caught.
Instead, he said the best deterrent was the prospect of being caught rather than what punishment followed.
He said evidence showed that people sent to prison were actually more likely to commit crime.
"Prisons teach crime, and longer sentences disable prisoners from going straight."
Kos also criticised the "incapacitation" principle - that longer sentences at least kept criminals off the street.
While there was some short-term truth, he said their eventual release meant there would be increased offending because of the way prison increased recidivism.
Longer sentences led to excessive spending on prisons, with each inmate costing $100,000 and the current prison population a billion dollar cost to taxpayers.
"Longer sentences represent a significant part of that cost, and they represent a significant diversion of funds from other constrained central government funding needs such as education and health."
Kos said: "Happily, we have an exceptionally safe society (second only to Iceland). Unhappily, we incarcerate excessively. It is a case of adjusting the balance."
Kos said sentencing options also needed to change to give judges greater flexibility, both in terms of home detention but also to allow possible retrospective reductions depending on how people served their time.
He said home detention in New Zealand had an "arbitrary" cut-off point of two years for those who did not pose a risk and had somewhere to go.
Kos said the "therapeutic advantages of home detention" currently saw "distortive sentencing" so as to allow the right candidates to qualify.
He highlighted the United Kingdom which had a four-year barrier and Norway which had no limit.
"We should consider following suit," he said.
Kos also said the lack of options beyond prison and home detention led to the "reprehensible" rejection of home detention for those who would most benefit if they did not have a home to go to.
"It is discriminatory against the already disadvantaged, and it demonstrates a woeful want of imagination on society's part."
Kos said New Zealand's binary approach to sentencing left judges with either prison or community-based sentences, when there should be other options.
"In Scandinavia many prisons are open institutions which provide that intermediate option. They are places which non-dangerous prisoners must attend.
"But they are humane. No walls, watchtowers or barbed wire. In some, no guards. Liberty is significantly restrained, but there is some semblance of normality.
"Interaction with the community remains possible; some measure of employment remains possible. It is a prison, but not as we know it. And we need it."
Kos spoke ahead of the Government's criminal justice summit, in a speech just published.
He said he expected the summit to discuss the issues raised in his speech, including the disproportionate level of Maori in prison - 15 per cent of the population but 57 per cent of the male prison population and 64 per cent of the female prison population.
He said the statistics "reflect the misdistribution of economic and educational poverty in this country and are a sorry stain upon our national character".
Minister of Justice Andrew Little would not comment - his office said he was offshore for a week and unavailable.
The issue is likely to be difficult politically for Little, with the National Party signalling it will pursue a "tough on crime" approach around changes to bail, parole and sentencing laws. The minister has said those laws should be considered as part of a review of the criminal justice system.
The NZ Herald has asked National Party leader Simon Bridges for the evidence he had cited saying deterrence worked in relation to the Three Strikes legislation. His office has said he would respond today.
Last week's summit will be followed by a number of other summits, including one focusing on Maori needs, one on victim needs and a number of regional meetings.