A law expert says the court system is fixed by understanding facts - not mandatory sentences

Justice Minister Paul Goldsmith hasn't ruled out the policy - which would see a minimum standard set for various crimes.

Judges currently have discretion to give discounts based on aggravating or mitigating circumstances.

Former High Court judge Sir Ron Young says New Zealand has a lot of people in prison as it is.

He says the courts are already on the heavy end of sentencing - people serve up to 20 years for murder compared to just ten, 30 years ago.