New World, Pak'nSave and Four Square supermarkets are reportedly using facial tracking technology to spot known criminals before they have a chance to act.
Stores in the North Island use a security system called Auror, the Otago Daily Times reports. The revelations came after a man was wrongly identified as a shoplifter by staff in a Dunedin New World.
The Times asked Foodstuffs, the chain's owner, if it used facial tracking technology. The company said it did, but not in the store where the man was wrongly singled out, saying that was human error.
Foodstuffs head of external relations Antoinette Laird said the Auror system is used in a "handful" of stores in the North Island, but wouldn't say which.
Z Energy also reportedly uses the Auror system, named after the title given to magical law enforcement officers in the Harry Potter series.
The Office of the Privacy Commissioner told the Times it didn't know supermarkets were using the technology, and said customers should be made aware they're being tracked.
"If individuals feel their privacy has been breached by this technology, they should complain to the supermarket first," a spokesman said.
"If they are unsatisfied with the outcome of that complaint, they can complain to our office.''
Chinese police have recently started wearing high-tech glasses which helps them pick suspects out of the crowd.