The effectiveness of the use of facial recognition technology in our supermarkets will be assessed by the Privacy Commissioner at the end of a six month trial

His inquiry will make sure the 25 Foodstuffs North Island stores in the trial are carrying it out in a way which complies with the Privacy Act.

Privacy Commissioner Michael Webster says they'll compare the data on harmful behaviour between stores in the trial and those not in it.

He says they'd want to see a pretty significant reduction in the incidents of violent harm, threats and assaults.