THe one of the face is to ID you, and the one in the barcode area is to work out if you've slapped a sticker for 1kg potatoes on a packet of 1kg of meat.
The face one is to show you that you're on camera, the other one is to detect the fruad. THe cameras in the ceiling aren't high enough resolution to work out if your doing a switcheroo or not.
Basically its a full service package. with the three cameras, it makes it very hard to argue that it wasn't you who did it, that the swap of barcode was a simple error, and that it was just a mistake.
The face one is to show you that you're on camera, the other one is to detect the fruad. THe cameras in the ceiling aren't high enough resolution to work out if your doing a switcheroo or not.
Basically its a full service package. with the three cameras, it makes it very hard to argue that it wasn't you who did it, that the swap of barcode was a simple error, and that it was just a mistake.