Swindlers can make a killing by passing off recently distilled whisky as old and rare Scotch, but the fallout from nuclear bombs can expose such fakery.

Bidders pay dearly for a wee dram of antique Scotch; one bottle fetched more than US$1 million in 2018. To foil counterfeiters, Gordon Cook at the University of Glasgow, UK, and his colleagues capitalized on twentieth-century nuclear-bomb tests, which added large amounts of the isotope carbon-14 to the atmosphere. Carbon-14 is absorbed by living things and decays at a known rate, which means that an organic sample — such as the barley distilled into whisky — can be accurately dated by measuring how much of its carbon is carbon-14.

The team collected samples of whisky with known production dates and measured the samples’ ratios of carbon-14, -13 and -12. The researchers then compared carbon-14 measurements from unverified booze with measurements from definitively dated samples — and found multiple imposters. One drink that was purported to be from 1863 was actually made between 2007 and 2014.