The privacy commissioner is keeping a close eye on a facial recognition technology trial starting at Foodstuffs North Island stores on Thursday.

The trial is happening because the commissioner asked Foodstuffs North Island to show evidence facial recognition technology was a justified way to lower retail crime.

Foodstuffs is proposing to use FRT to scan and make a biometric template of each shopper as they enter the premises to see if they match a watchlist of people identified with repeated harmful behaviours.

It follows 4719 incidents of retail crime reported across Foodstuffs stores in the last quarter of 2023, including 513 trespass breaches - up 52 percent on the previous quarter.

Foodstuffs North Island chief executive Chris Quin said the trial was important because the company hoped to establish whether facial recognition would keep staff and customers safe without compromising their privacy.

"Shockingly, one of our security team was stabbed recently and our people are being punched, kicked, bitten and spat at. We're seeing over 14 serious incidents a week, including an average of two assaults," Quin said.

"All too often it's the same people, coming back to our stores despite having already been trespassed, committing more crime, and often putting our team members and customers at risk of abuse and violence."

Facial recognition had the potential to help by identifying repeat offenders when they tried to come back into stores, he said.

All images in the facial recognition would be instantly deleted unless a person had committed a crime, been aggressive, violent or threatening towards workers or customers or had actively assisted in such harmful behaviour. "This is a high threshold."

The trial starts on Thursday across 25 stores over six months and the data will be used to decide whether or not to roll-out the technology further.

Privacy Commissioner Michael Webster thinks the technology is something all New Zealanders should be concerned about because of its privacy implications and he fears it is not a proven tool to reduce harmful behaviour including violence in supermarkets.

"New Zealanders deserve to shop for their milk and bread without having their faces scanned unless it's really justified.

"We wouldn't accept being fingerprinted and checked at the door before shopping for groceries - that sounds ludicrous - but FRT is a similar biometric process that is faster, machine-run, happens in a nanosecond, and creates a template to compare your face to, now and in the future," he said.

He is also worried about what it means for Māori, Pasifika, Indian and Asian shoppers since the software is not trained on the New Zealand population.

"I don't want to see people incorrectly banned from their local supermarket and falsely accused," Webster said.

The commissioner will consider if any further action is needed to protect New Zealanders' privacy during the progression of the trial.

"The trial itself is not without risk given the effectiveness of the technology and the operational protocols are untested in a supermarket setting. The franchised nature of the Foodstuffs North Island operation also means that individual owner-operated stores who participate in the trial are responsible for decisions about what they do and how they use the data they collect. This is another reason for keeping a close eye.

Unmatched people's images would be promptly deleted following feedback from the Privacy Commissioner's office while matched people would be banned or removed from stores.

In some cases the police would be involved.

'Honest customers have nothing to be concerned about' - Foodstuffs North Island general counsel Julian Benefield

The trial of the FRT was solely aimed at improving retail security and would not be used for any other purpose, Foodstuffs North Island's general counsel Julian Benefield told Morning Report.

"This is all about us meeting our moral and legal obligations to keep our store team members safe."

He said there had been a "massive increase" in retail crime in the organisation's stores over recent months.

"We've seen our store team members being stabbed, punched, kicked, bitten and spat at and we've found that repeat offenders are responsible for around a third of all incidents."

Foodstuffs had, on the advice of the privacy commissioner, appointed an independent evaluator to ensure the trial respected customer privacy, Benefield said, and there were safeguards in place to address concerns over people being mistakenly identified as previous offenders.

"There is a threshold set in terms of accuracy before a repeat offender is matched in the system, and then, most importantly, there is a human element where two highly-trained staff members must check that it is in fact the person - which is what already happens in most of our stores today in terms of dealing with violent and repeat offenders."

Benefield said in many cases those identified by the technology would already have been trespassed by stores "but what is really difficult for our team members - especially in busy stores - is that it can be really difficult to remember all the people who've been trespassed".

He said the company wanted to be "very transparent" with its customers about what it was doing and the fact the trial was taking place would be clearly signposted in the affected stores.

"We are respecting customers' privacy, we're also doing more to keep our team members and customers safe."

Those who were not repeat offenders had no reason to be concerned, he said.

"If you're an honest customer coming in, who is not a previous offender, that (image) will be immediately deleted, so those honest customers have nothing to be concerned about. It will only be a match if it is a previous offender."

Benefield said the trial was just that at this stage and no decisions to roll it out on a broader basis had yet been made.

Customer feedback would also be taken into account as the trial progressed, he said.

Use of technology needs to be 'fully justified' - privacy commissioner

Webster told Morning Report he would be using his powers of inquiry under the Privacy Act to keep a close eye on the trial.

"We'll be monitoring to see if it does actually result in a decline in numbers of violent incidents at supermarkets, which is obviously one of the aims from it."

His office would also be looking at the assessment completed at the end of the trial by the independent evaluator to check that it had delivered what was intended, he said.

"As a general proposition, we're not in the business of banning technologies but ensuring that they're used in an appropriate and safe way, so that their use is fully justified - that's what our legislation, or act, asks us to keep an eye on."

"That's why this trial is so important."

Webster said his office had the power to issue a compliance notice to an organisation directing it to stop using technology in some instances.

"At the end of the day, if, in our assessment we consider the use of ... privacy-intrusive technology is unlawful, we can issue a compliance notice directing an organisation to take steps to stop using it in that particular way."

"I understand businesses' concern to protect their staff and customers and I want people to be safe as they shop and they go to work, but that's why we need to be really careful to analyse the data that Foodstuffs has and will capture over the trial, to see what sort of incidents are happening."

Foodstuffs North Island had "literally, I understand, millions of customer visits every week and a relatively small number of incidents a week".

"So we need to be careful that we when we look at the data we're doing a full and thorough analysis of what actually is happening."

When Foodstuffs announced the trial in December 2022, it said existing FRT would be turned off awaiting its outcome.

Main image (Suppled/Foodstuffs): A trolley of groceries containing Foodstuffs' products.