A German supermarket chain is to offer fingerprint billing to more customers after a successful trial run at a store in the south-western town of Ruelzheim.
The likelihood of a mix-up is said to be one in 220 million
Specially registered Edeka shoppers can pay by placing their finger on a checkout scanner, avoiding the need for cash or payment cards.
About 100 customers have joined the scheme since its launch in November.
The store plans to introduce its biometric payment option to other branches from April.
Customers must submit their fingerprint and bank details to join the scheme, which was hailed by shoppers interviewed by the Associated Press news agency.
"I can practically leave my purse at home without having any problems paying for anything," said customer Miriam Kleck.
"You just press down your finger and you're done."
Print payments are treated like normal card transactions.
Fingerprint templates are stored on a local server which manufacturers say cannot be accessed from outside but some consumer groups are concerned about security issues.
"We see the risks that arise from the data-gathering and also the insecurity factor which is inherent in this process, as more serious than the advantages," said Evelyn Kessler, spokesperson of the Consumer Advice Centre in the Baden-Wuerttemberg region.