Human rights lawyer Michael Bott has described the actions of Palmerston North police as draconian and overkill in taking DNA samples from a man convicted of stealing vegetables.
The man stole vegetables from his neighbour's garden because he was hungry.
Inspector Pat Hancock said it is policy in his area to take DNA samples no matter how serious the crime, and the law allows for this.
He said if criminals know their DNA is held they might think twice about committing crime in future.
However, lawyer Michael Bott said police should use the discretion they are allowed.
Mr Bott said proposed law changes which will allow those simply charged with an offence to provide DNA samples is of huge concern and there should be more public debate.