When she wandering into a Home Bargains store to pick up some chocolate to take the edge off a bad day, a woman who wishes only to be identified as “Sara” says she was accosted by a store employee less than a minute after entering. The employee told her she was a thief, and asked her to leave.

The source of the accusation was Facewatch, a facial recognition system now being employed in a variety of stores throughout the UK—including Budgens, Sports Direct, and Costcutter stores—to identify shoplifters before they strike again. The system flagged Sara because of a false match to its database of problematic faces.

After she was asked to leave, Sara says that her bag was searched and she was then accompanied outside, where she was told that she has been permanently banned from all stores that use Facewatch.

Sara later received a letter from Facewatch, admitting to their error. While the company declined to offer comment to reporters regarding Sara’s case, it did say that its product helps protect public-facing workers and prevent crime.

Home Bargains also declined to comment on the incident.

Retailers, it seems, are not the only ones who are rolling Facewatch and similar technologies into their day-to-day operations. Police in East London are using the technology in conjunction with ubiquitous surveillance cameras, which tirelessly capture facial images as people move through the area going about their business. Facewatch sorts through the images, and if it discovers anyone whose face matches someone on a police watch list, they are stopped, interviewed, and sometimes arrested by police.

Some commentators have said that such technology turns the individual into a product, and his or her face into a bar code. During a BBC special reports ride-along, the London Metropolitan Police told reporters that they made six arrests in a single day, all enabled by Facewatch. Police defended the advantages of the technology, but civil liberties groups are raising the alarm about its reliability and its morality.