by CAROLINE GRAMLING
Cold case files: Light and heavy isotopes forging forensic “isoscapes”
Law enforcement may have a new tool, courtesy of geoscientists. About five years ago, scientists coined the word “isoscape” to describe a new kind of map: a spatial distribution of stable isotope ratios (from elements such as carbon, hydrogen, oxygen, nitrogen and strontium) in different parts of the world, based on known ways that these isotopes behave in the environment. Different isotopes tell different stories — carbon can help identify diet, while hydrogen and oxygen can help identify provenance (for example, about 30 percent of the hydrogen deposited in a human hair comes from the water or water-based beverages the person drank) — so the combination of different isotopic values into one map creates a far more powerful tool than a map based on any single element.
The potential usefulness of isoscapes is wide-ranging and thrilling: By measuring the isotopic ratios in anything from bones to hair to plants to gems, and then comparing those values (perhaps even changing over time, as bones, plants and teeth grow) with an isoscape, it might be possible to track human geographic origins, identify the source of illicit drugs, detect counterfeit food products and follow the migration of wildlife.
The potential for using stable isotopes in forensics is certainly of interest to police. One of the most interesting and unusual presentations in the EGU meeting session was a poster by geochemist Wolfram Meier-Augenstein (one of the conveners of the session) of the James Hutton Institute in Dundee, Scotland, geochemist Helen Kemp, also of the James Hutton Institute, and other colleagues. The police force of Gwent, in South Wales, approached them to do a stable isotope analysis on the remains of an unidentified Asian man, to see if he could be identified somehow.
Using stable isotopes from a hair on the man’s head — of a length coinciding with about 14.5 months of life — the scientists were able to sketch out the man’s last year of life, which included several months spent in Eastern Europe, a longer stint in Central Europe, and then finally arrival in the U.K. about three months before he died. That information — combined, it should be noted, with additional data from Interpol that began to unfold as the case progressed — ultimately led to his identification: He was Vietnamese, a victim of human trafficking, and had been killed by a Vietnamese organized crime gang for not repaying a debt. The gang, it seems, was in the habit of bringing people in through Eastern Europe, then Central Europe, and finally depositing them in the U.K.
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