Questions are being raised about how far the police collection of DNA should go.
Under New Zealand law, the police can take DNA from people they plan to charge and match it against samples from unsolved crimes.
Collections of DNA were expanded by the government in 2009 which said it was critical for fighting crime.
Thousands of samples are taken from suspects every year and they can be taken from anyone facing prison.
Nessa Lynch from Victoria University is taking part in a three-year research programme looking at the collection and retention of DNA.
She told Radio New Zealand's Nine to Noon programme, that there are good arguments when dealing with a suspected violent or sexual offender because of definite public safety issues.
But she said there are fewer arguments for taking DNA from people due to be charged with a minor offence.
Dr Lynch said there are no reliable statistics which can pinpoint DNA samples as being the sole reason behind later convictions.
