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.
“We were pleased that they did,” Cerling said.
He said drinking water left an isotope signature in the growing hair. Even people who drink bottled water still use tap water to make coffee or tea or cook pasta, he said. “You really do use a lot of local water in your everyday activities.”
The researchers said isotope concentrations in drinking water varied because of regional differences in rainfall and evaporation. Cerling said researchers could probably tell the difference between Utah and Texas, but not necessarily between Chicago and Kansas City.
Police officers are already using the tool to help identify a possible murder victim.
Todd Park, a sheriff’s detective in Salt Lake County, Utah, sent Ehleringer hair samples from a woman whose remains were found near the Great Salt Lake in October 2000.
An isotope analysis of the victim’s hair showed she had moved around several states in the Northwest. The researchers plan to do an analysis of her teeth to see if the isotopes can reveal where she grew up when the teeth were forming.
“Every little bit helps,” Park said in a statement. “This is definitely something that will give us a piece of the puzzle.”
The researchers said the work had generated a lot of interest from police, but Cerling said the tool could also be used in anthropology and archaeology. “I also think it will have some interesting applications in wildlife conservation,” he said.
Editing by Will Dunham and Peter Cooney