Justice Minister Simon Power says safety mechanisms are in place to ensure major changes to the court system that came into effect on Monday do not lead to miscarriages of justice.
The series of laws are one of the biggest revamps of the New Zealand justice system in its history, and include allowing juries to reach majority verdicts rather than requiring a unanimous decision.
One of the most contentious changes, whichaims to take pre-trial hearings from courtrooms to court offices, has attracted criticism.
In most cases, instead of evidence being examined in court to decide whether a case will go to trial, it will be handed in written form to court staff, who will make the decision.
Criminal Bar Association President Anthony Rogers says it is important that defence lawyers are able to cross-examine crown witnesses because they often say more than they do in written statements.
He says the changes will prevent vital evidence from being revealed in some cases and could lead to miscarriages of justice.
However the minister, Simon Power, told Morning Report a number of checks are in place to ensure the new regulations work, including a review by the Solicitor General after two years.
Mr Power says the changes are aimed meeting the needs of victims, witness and others in a timely fashion, and cost savings will happen as a by-product.
Auckland Crown Prosecutor Simon Moore says the impact of a change to the way the justice system operates will depend on how the courts interpret it.
He says both defence and prosecution lawyers have seen depositions hearings as a way to give their witnesses a bit of a dummy run - which is not what they are designed for, so the new law will restrict that practice.
Majority jury verdicts allowed
In another change in effect from Monday, juries will no longer need to agree unanimously on a verdict.
Only 11 out of 12 people on a jury now need to agree on whether they should convict or acquit someone accused of a crime.
The Law Society says the changes should result in fewer hung juries and therefore fewer retrials, which should both save money and free up court time for other trials.
The Society says the change brings New Zealand in line with most other Commonwealth countries.