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Wednesday, February 27, 2008

A New Tool for Crime Fighters

Analyzing a person's hair can help reveal where she's been.

By Brittany Sauser

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Hair analysis: Using a mass spectrometer (top), researchers measured the hydrogen and oxygen isotope ratios in hair and drinking water. After correlating the results, the team generated maps that show the predicted average hydrogen (top map) and oxygen (bottom map) isotope levels in human hair across the United States. The ratios of hydrogen-2 to hydrogen-1 are highest in the red and orange areas of the top map, and lowest in the blue and darker green areas. The ratios of oxygen-18 to oxygen-16 are highest in the red and orange areas of the bottom map, and lowest in the blue and darker green areas.
Credit: University of Utah

Identifying murder victims and tracking serial killers are daunting tasks for detectives when there is minimal scientific evidence available. Now, a strand of hair could provide valuable clues about a person's travels. Researchers at the University of Utah say that they are able to determine a person's recent travel history by comparing the isotope ratios of oxygen and hydrogen in a strand of his or her hair. The extent of the information that can be deduced is dependent on the length of the hair.

Hair is like a tape recording of your diet, says Thure Cerling, a co-leader of the study and a professor of geology, geophysics, and biology at the University of Utah.

The study, which was published February 25 in the Proceedings of the National Academy of Sciences, found a strong correlation between the isotopes in the water that a person drinks and the isotopes in her hair.

"Hair isotopes reflect body water, and, in turn, body water reflects drinking water," says Jim Ehleringer, a professor of biology at the University of Utah, who is co-leading the study with Cerling.

Ehleringer and Cerling developed a model to predict the geographic region of origin and travel history of humans based on the stable isotope composition of their hair. The researchers collected samples of tap water from more than 600 cities across the United States, as well as hair samples from the "trash clippings" of barbershops in 65 cities in 20 states, says Cerling. "We chose barbershops in smaller cities, where travelers are less likely to be," he adds.

Using a mass spectrometer, the researchers measured the levels of hydrogen isotopes (hydrogen-2 and hydrogen-1) and oxygen isotopes (oxygen-18 and oxygen-16) in the water and hair.

Based on the correlation of the isotopes in hair to those in drinking water, the researchers generated maps (see image below) that indicate the isotopic makeup of a person's hair with different regions in the country.

"Based on the map, we can ask whether or not the isotopes in hair are consistent with or not consistent with the region where the hair was found," says Ehleringer. If they're inconsistent, scientists can try to deduce what region the hair appears to come from and the travel history of that individual, he says.


Researchers have generated maps that show the predicted average hydrogen (top map) and oxygen (bottom map) isotope levels in human hair across the United States. The ratios of hydrogen-2 to hydrogen-1 are highest in the red and orange areas of the top map, and lowest in the blue and darker green areas. The ratios of oxygen-18 to oxygen-16 are highest in the red and orange areas of the bottom map, and lowest in the blue and darker green areas.
Credit: University if Utah

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Comments

  • How about world wide? Seasonally?
    nekote on 03/01/2008 at 9:53 AM
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    3/5
    This is interesting.

    Seems that climatic temperature is a significant, though not sole, factor for both H2 and O2 isotope ratios.

    The O-16 to O-18 is widely used as the root of the temperature assumptions about the past, in discussions of Global Warming.

    I wonder what these H2 and O2 ratios look like on a planetary scale.

    And, on a seasonal basis, per locality.

    Lastly, why the significant "hot" spot north of central Texas?  And that opposite ("cold"?) area towards the adjacent boundaries of Idaho, Montana and Wyoming?
    Rate this comment: 12345
    • Re: How about world wide? Seasonally?
      martinaatayo on 03/02/2008 at 4:58 PM
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      26
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      Except otherwise, and based on the
      above experimental description that
      generates sense of curiosity, finding
      might tend to offer "open ended",in lieu
      of "closed ended" experimental conclusive
      results.(martin@mpgatechnology.com)
      Rate this comment: 12345
    • Re: How about world wide? Seasonally?
      theTonster on 03/03/2008 at 12:24 AM
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      2
      Good Point.
      Also note the color scale goes opposite for the deuterium ratio w.r.t. delta-18-O: a possible legend glitch? Second, If you’ve been to Fort Worth or Yellowstone, that would be useful, but if you went from SFO to Boston your hair’s isotopic ratios wouldn’t change at all. Large areas of the US share that concentration. I don’t see this being all that useful, outside the extremes.
      Rate this comment: 12345
  • Now criminals will take water with them
    michro on 03/04/2008 at 1:11 PM
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    3
    and use this technique to "prove" they have not been in the area where they performed the crime
    Rate this comment: 12345
  • Very Detailed Maps
    bojo42 on 03/08/2008 at 1:03 PM
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    1
    If the researchers only collected water samples from 600 locations, and presumably hair samples from a subset of those same locations (or even if they are from different locations), how can the maps have as much detail as they show?  If you have 600 data points and 48 states, that works out to a paltry 12 data points per state.  I wonder if I could generate a map with the detail which California has, using all 600 data points.  Or am I overlooking something?
    Rate this comment: 12345
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