Statistics New Zealand - crime and justice statistics
New Zealand Police statistics - provides access to policedata.nz which creates reports on a range of topics
Ministry of Justice: Research and Data includes:
New Zealand Crime and Safety Survey
New Zealand Crime and Victims Survey
Data tables on specific offence types and population groups
Department of Corrections Research and Statistics
Quarterly prison statistics (Department of Corrections)
New Zealand Family Violence Clearinghouse - family violence statistics
Historical:
New Zealand Official Yearbook 1872-2012 (Browse yearbook by topic - Justice and Law)
Customised data requests:
Statistics New Zealand - Customised data requests
For data that is not publicly available through the Statistics NZ website.