The police use of cameras that identify car number plates to support criminal cases is being challenged in four different court cases.
Thousands of automated number plate recognition (ANPR) cameras across the country are accessed by police hundreds of times a day.
But at least four separate cases are challenging the admissibility of the images they produce and they are set to be heard in the Auckland District Court next month.
One involves ANPR images from a petrol station forecourt that police used to try to link a woman to a crime elsewhere. Police would not comment on any of the active cases.
Two cases are from the Public Defence Service (PDS), which has argued that police have slipped into using mass surveillance without adequate checks and balances.
However, a court has already rejected similar arguments.
In the ruling in May at the Christchurch District Court, the judge said the use of ANPR was not the same as a search, was not used like a "tracking device" and had enough safeguards around it.
ANPR led to "greater ease and greater transparency", Judge J Farish said.
But defence lawyers said that ruling needed to be tested.
Mark Ryan - a barrister in one of the four Auckland cases - said: "It would be wise to have the matter heard by superior courts [because] of the continued reliance by police on this information-gathering facility."
"For the defence, it is an extremely difficult problem."
Police under a contract with ANPR company Auror had access to the information, which Ryan said was "circumventing the law in relation to taking shortcuts".
The law gave police the ability to apply for production orders or search warrants, which were under judicial oversight, but instead they used ANPR where there was no such oversight, he said.
Courts in the United States have also recently been grappling with this in Nevada and Florida.
Both Ryan and the PDS said it was proving difficult to get vital information.
"We are continuing to face difficulties in obtaining the required information from Auror to assess the scope of the surveillance undertaken through Auror, for example the number of cameras contributing to the network," said the PDS, which provides representation to people who have legal aid in criminal cases.
The PDS had sought a court order to get disclosure of the information.
Auror told RNZ it worked with retailers and police to make recording, reporting and investigating retail crime simpler.
"We are focused on addressing the harm that this crime causes in our communities.
"The admissibility of ANPR evidence is something that the courts are well placed to determine," it said on Wednesday
The PDS was involved in the Christchurch District Court case, which related to five robberies of small retailers by masked robbers armed with a sawn-off shotgun, a rifle, a hammer, a baseball bat, and a tomahawk. The case resulted in convictions.
Police used ANPR to identify two of the vehicles involved.
In that case, the Court of Appeal sent the challenge over ANPR back to the district court, stating:
"Proper consideration of the new arguments requires more extensive evidence about the Auror system and its use by the police than has been presented.
"For example, how the system was designed, to what extent is it funded by police and tailored to meet police requirements, how ubiquitous are the cameras that contribute data to the platform, to what extent is it possible to trace an individual's movements by accessing the system, and what is the level of intrusion into personal privacy.
"This Court is not well-placed in the context of a pre-trial appeal to make what in effect would be first instance factual findings bearing on the admissibility of evidence. "
The Christchurch ruling was one of the first times the legal reasons to support using ANPR cameras this way have been made public, but RNZ understands there were several other earlier rulings like it.
RNZ will report on those reasons tomorrow.
The police told RNZ that in cases where judgements have been given, "the court has decided this evidence was lawfully obtained and is admissible at trial".
ANPR "is a well-established technology used all over the world to read vehicle number plates. It enables police to work more effectively and efficiently", police said in a statement.
Police referred to its policy on ANPR's use, audit and data retention This policy was developed years after police contracted with Auror in 2015, and also after police encouraged the expanded use of the technology, as RNZ has previously reported.
In the US, at least 16 states have laws specific to ANPR but New Zealand does not. It relies on the Privacy Act, and police internal policy.
Thousands of officers are authorised to access the images. For still images, no warrant is needed, but if police want to track a vehicle via ANPR, that needs a warrant. The court challenges involve still images.
The Christchurch court ruling from a September 2023 hearing said it was confirmed that police use of ANPR "has grown exponentially over the past two years and has assisted greatly with respect to police investigations and the detection of criminal offending".
A defence lawyer's written defence on one of the Auckland cases - of the woman in the petrol station forecourt - compared it to a "Big Brother nightmare scenario".
"A citizen when they go to a petrol station have the right to presume that they are not being surveilled retrospectively by the police by a system designed to prevent supermarket theft," said the submission, which has not been ruled on.
"This is akin to the 'Big Brother' nightmare scenario." ANPR at a supermarket was different as the footage was provided by the retailer to the police by consent immediately following the crime in the supermarket.
"It is another thing for a public organisation to go looking for alleged crimes after the event when no crime has occurred to the petrol station owner."
Auror is based in Auckland and uses its partnerships with various local police forces to market its anti-retail-crime platform here, and in Australia, the UK and US.
A second company, SaferCities, also runs ANPR with police, but on a smaller scale.