Using Evidence to Build a Better Justice System: The Challenge of Rising Prison Costs

The report analyses the reasons why New Zealand’s prison population is high relative to other countries.  It argues that the high prison population has been driven by factors other than evidence about what works to reduce crime. These factors include negative public perceptions that are driven by the media.

The report points out that, although it will always be important to have a subset of people in prison to protect the public, prisons are not a good solution to the problem of crime. 

It outlines the strong evidence for putting resources into:

  • crime prevention,
  • early intervention, and
  • a smarter approach to rehabilitation and subsequent social inclusion for those already in the criminal-justice system.

Key findings

  • New Zealand’s prison population is one of the highest in the OECD, at around 220 per 100,000 compared to an OECD average of 147 per 100,000.
  • New Zealand’s recorded crime levels are the lowest since the late 1970s. Crime rates have fallen steadily since 2009.
  • Evidence suggests that prison growth has been driven largely by ‘tough on crime’ policies.
  • Ministry of Justice calculations estimate that if ‘tough on crime’ policy changes since 2000 had not been made, the prison population would be 8,800.  The actual prison population in 2018 is 10,600.
  • Pre-trial detention (that is, people being ‘remanded in custody’ while awaiting a trial for their alleged crimes) has a ‘criminogenic’ effect on those remanded, e.g. people lose jobs, homes, relationships, acquire more criminal skills and build more offender-based social networks.
  • There is no evidence that tougher parole laws have a ‘deterrent’ effect.
  • The Parole Act 2002 increased the proportion of sentence served from 50% to 75% for people with sentences of 2 years of more.
  • The total cost of prisons has doubled since 2005, and tripled since 1996.
  • Prevention programmes are an effective way of reducing long-term criminal justice costs.

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