Sexual offenders are among criminals given the opportunity to appeal their convictions after a police audit of hundreds of prosecutions since 2008 found mistakes.
The "comprehensive" audit of 663 prosecutions found 10 cases where charges were filed without consent from the Attorney-General, that resulted in a conviction.
Four were for sexual offences under the Crimes Act 1961, three were for inciting racial disharmony under the Human Rights Act 1993, and there were three offences under the Aviation Crimes Act 1972.
But without consent the convictions are deemed unlawful, police said.
The previously convicted criminals are now eligible to file appeals to have their convictions overturned, with police even offering to facilitate legal representation.