Police software that automatically collects numberplates to nab offenders could be illegal, the privacy commissioner says.
The tracking technology, known as automatic numberplate recognition, has already been condemned overseas, where critics have likened it to Big Brother-style surveillance.
The New York Police Department used it to spy on mosques and track worshippers through their numberplates.
In New Zealand, it is still being tested by police, but the Office of the Privacy Commissioner has questioned whether even a trial is legal.
There are particular concerns about police gathering information without people's knowledge, which could then be retained and possibly used for other purposes.
Yesterday, assistant commissioner Katrine Evans said she was still talking to police about how the technology would be used appropriately, if at all.
"Key things . . . are to make sure it's correctly targeted and effective, that people are told what's going on wherever possible, and that data relating to irrelevant vehicles is wiped very quickly," she said.
Police say there have been no privacy breaches and the technology is essentially a more efficient version of an officer manually checking numberplates.
The technology automatically photographs numberplates and then quickly matches them against a pre-selected list.
If the numberplate is flagged, the vehicle can be stopped quickly by a police "intercept team".
Police have been testing the technology for the past two years, driving unmarked vans through Wellington to capture random numberplates.
The trial has been used to identify disqualified drivers, stolen vehicles and other "vehicles of interest". Police can also use it to check alibis and track the movement of vehicles used in a crime.
In one trial, officers worked with the Justice Ministry to track down fine dodgers by using their numberplates.
The police manual on the technology prohibits gathering information on anyone not suspected of "unlawful activity".
National road policing manager Superintendent Carey Griffiths said police were working with the commissioner to deal with privacy concerns.
In the past, hard drives connected to the cameras had stored data for two months, but that had been switched to 48 hours to better protect privacy protection.
He stressed police were checking numberplates only against their "vehicles of interest" lists, and no data was kept on other cars or individuals.
"There has been speculation that police are doing the Big Brother thing," he said. "But the only people that need to worry about this are criminals and people that shouldn't be on the road."
Police already checked numberplates manually against criminal databases. The new technology simply speeded up the process.
- Fairfax Media