Police cells around the country will be inspected for signs of "torture" by the Independent Police Conduct Authority - as part of New Zealand's obligation under the United Nations' Optional Protocol to the Convention Against Torture.
The IPCA will be looking for "serious abuses of detained persons".
New Zealand, Honduras, Burkina Faso, Sierra Leone and Togo are among the 57 signatories.
Australia, Iran and Iraq are some of those who have not signed.
The IPCA statement of intent released yesterday says it will inspect 30 detention facilities before June 30.
It will work with the "Central National Preventive Mechanism" against torture, the Human Rights Commission, and report its results to the public.