Reader Benedict Loh wrote in to askST: "I would like to find out if I were to bring in a product purchase from store A into supermarket B, would supermarket B be able to determine if that product was not taken from their supermarket? Would there be a situation where I am alleged to have stolen that product if I did not present it for payment?"
Consumer reporter Jalelah Abu Baker checked with supermarket chains NTUC Fairprice, Sheng Siong and Giant on this.
While some products, like house brands and fresh items packed in-house have unique packaging and are easily distinguishable, supermarkets will not be able to tell if other, more common items are bought in their stores, or other stores.
Supermarkets advised shoppers to retain their proof of purchase, to avoid potential misunderstandings since similar products are sold widely across various supermarkets.
When products have an international standard barcode, which many products like drinks, snacks and canned food do, they cannot be differentiated by which store they came from.
To establish if a potential shoplifting incident has taken place, major supermarket chains typically deploy uniformed and plainclothes security officers, supported by closed-circuit television systems.
These security officers are specially trained to recognise suspicious behaviour and observe standard operating procedures to identify potential incidences of misappropriation.
Suspected cases will then be referred to the authorities for further investigation to ascertain if a customer has shoplifted.
Customers making trips to different supermarkets in the same day should keep their receipts in the case that they need to show proof of where they purchased an item from.