Lesley Chesson holds up one of nearly 2,000 human hair samples stored at the company IsoForensics. Courtesy of Ari Daniel Shapiro/WGBH Educational Foundation

You are what you eat, and what you eat ends up in your hair. Scientists in the U.S. and Europe have used this basic idea — and some sophisticated isotopic analysis — to devise a sort of hair-based GPS tracking system. A single strand contains information on your whereabouts over the past few months, a fact that law enforcement agencies are now using to solve crimes.

Lesley Chesson opens a cardboard box inside her office at IsoForensics, a Salt Lake City-based company that uses science to fight crime. She pulls out a bulging manila envelope.

"That one definitely has hair in it," she says with a chuckle.

A senior scientist at the company, Chesson reaches into the envelope and removes a mass of brunette hair. Her colleague, Luciano Valenzuela, looks over a list to see where it came from.

"It's hair from Shawnee, [Oklahoma]," he says.

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Source: PBS