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Sunday, July 20, 2008

Geochemist's Skills Handy in Crime Case

By Hailey Heinz
Journal Staff Writer
       Nelia Dunbar usually spends her days studying the science of volcanos. But, once in awhile, her skills are tapped to help unravel the mysteries of crime, not nature.
    Dunbar, a geochemist and adjunct professor at New Mexico Institute of Mining and Technology, was asked to help solve the death of Thomas Hickman.
    Hickman's body was found near Santa Rosa in March, shot in the back of the head with his mouth duct taped shut. A gun was found nearby, attached with ribbon to helium balloons that were ensnared in a cactus. State Police initially investigated the case as a murder, but have recently ruled that it was an elaborate suicide.
    Dunbar is the manager of the Electron Microprobe Lab at NM Tech, which is the only lab in New Mexico with microprobe technology, and one of just a handful of such labs in the country. Dunbar's role in the case involved metal shavings found in Hickman's garage. The serial number had been filed off the gun used to kill him, and Dunbar was asked to determine whether the tiny metal shavings came from that same gun.
    The technology she uses is complicated and specialized. First, Dunbar had to polish the tiny metal shavings to what she called "a mirror finish" so that no outside particles could interfere with the test. Then she hit the shavings with an electron beam. Through a process that affects the individual atoms in the metal, she was able to determine that the metal was mostly aluminum, with some additional zinc, copper and magnesium. Dunbar was also able to determine the exact percentage of each metal. When the same tests were run on the gun, the metals matched up — and sealed the authorities' case.
    "It was one of the most, if not the most significant, piece of evidence," said New Mexico State Police Agent Eric Schum.
    Dunbar said the chemical makeup was so similar that it would either have to be from the same gun, or from a gun "made at exactly the same time in exactly the same factory."
    Dunbar said she mostly uses the technology to trace volcanic ash, but she has done other crime work in the past, once helping police match up a bullet fragment to the rest of a bullet.
    Although she enjoys the challenge of crime-related work, Dunbar said the pressure is greater.
    "It's actually a little bit scary," she said. "Somehow, the stakes are higher, and it adds another level of seriousness."
    Dunbar said she doesn't know many details of the Hickman case because she wanted to remain unbiased so her results would only reflect the pure science.
    "For this kind of work, I prefer not to know a lot about the case," she said.