Hair analysis offers new crime-fighting clues

By Julie Steenhuysen

CHICAGO (Reuters) - Scientists can now tell where in the United States a person may have been by analyzing a single strand of hair, offering a new tool for crime investigators trying to identify a body or track criminals.

They said variations in hydrogen and oxygen isotopes found in hair could be matched to the regional tap water people drank, providing clues about where a person had been living.

"In people with very long hair, you could get quite a long history," said University of Utah geologist Thure Cerling, whose findings were published in the journal Proceedings of the National Academy of Sciences on Monday. The tool would work best on hair samples taken from the head because hair grows continuously there.

Cerling and University of Utah biology professor James Ehleringer developed an elaborate map that details regional differences in the hydrogen and oxygen isotopes based on tap water samples from 65 cities in the United States.

To do that, Ehleringer sent his wife and a friend on a road trip to collect water and hair samples from barbers in towns in southern, central and southwestern states. Cerling's children covered the northern United States.

They only gathered samples from cities with 100,000 or fewer people to ensure that hair samples were from local residents rather than tourists.

"With the whole U.S. blanketed with samples of drinking water, we can see in the drinking water where the big gradients are," Cerling said in a telephone interview.

Then they looked to see if the same isotope patterns matched the hair samples.