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The proof is in the fiber
September 1, 2011
|Doug Beussman watches Jason Eckmann prepare a cotton sample for analysis.|
Suppose that fibers from a white T-shirt are found at a crime scene. When tested against fibers from a shirt strewn in the prime suspect’s closet, they are found to be a perfect match. Case closed? Not exactly. But such a match would certainly be a key piece of circumstantial evidence.
Although fiber analysis is not new to forensic science, St. Olaf Associate Professor of Chemistry Doug Beussman '92 thinks that it could be utilized in a new way to solve crimes. He has previously focused much of his research on drug analysis, and even spent his sabbatical last year working for the FBI.
This summer, he and student researcher Jason Eckmann '12 worked to see if it was possible to differentiate between the cotton fibers found in different brands of white T-shirts, cotton towels, and basic white cotton material. Though these fibers are all similar and often cannot be distinguished under a microscope or with other tests, they do exhibit differences as a result of varying environmental factors in the region and year in which the cotton was grown. Utilizing isotope ratio mass spectrometry, these minuscule differences can be detected.
|A tiny strand of fiber is all that's needed for analysis.|
St. Olaf acquired an isotope ratio mass spectrometer a couple of years ago as the result of a grant application written by Beussman and several other St. Olaf faculty members. Because Beussman was working with the FBI last year, this summer was his first chance to use the instrument in a research project. Isotope ratio mass spectrometers are already used by organizations like the FBI to determine the origin of illegal drugs, so Beussman thought that similar methods would work with cotton, since it also is plant-based.
Jockey or Hanes?
To test the T-shirt hypothesis, Beussman and Eckmann used several brands of white cotton undershirts, as well as white cotton towels and plain white cotton material. They were interested in seeing whether they could differentiate between these items based on the isotope ratio found in the fibers. To find this ratio, they cut small pieces of the fabric and burned them. When burned, the sample emitted gasses containing elements like carbon and hydrogen, which the mass spectrometer could measure and use to determine the isotope ratio of the elements.
In a forensics lab, a scientist would compare the isotope ratio of a fiber found at a crime scene to that of a fiber from a T-shirt found in a suspect’s home. If the ratio was different, then they could conclusively say that the fiber at the crime scene did not come from that specific shirt from the suspect’s closet. But if the ratios matched, then they could conclude that there was a strong likelihood that the fiber came from the suspect's shirt.
|The sample is wrapped in foil before being fed to the isotope ratio mass spectrometer for analysis.|
"It worked better than I anticipated," says Beussman of the research process. By the end of the summer, they were able to successfully distinguish between three brands of the same white T-shirt, the cotton towels, and the fabric. Eckmann also found that fibers from the front panel of a shirt sometimes exhibited differences from fibers from the sleeves or back panel. He noted that the stitching expressed a different ratio, even though it looked quite similar to a fiber from the actual shirt.
Based on these findings, they realized that if a T-shirt was found at a crime scene, several small samples from various locations on the shirt would be needed to make any sort of judgement about either a positive or negative isotope ratio match.
Freedom to research
This was Eckmann's first summer conducting research outside of coursework, and he thoroughly enjoyed the challenge. "Instead of following directions from lab manuals, I was able to collaborate with a professor and have much more freedom to research at my own pace and with a little bit more personal direction," he says.
Research is not without challenges, of course, and Eckmann acknowledged these as well. When he and Beussman started their research this summer, nothing had been published on this particular topic. Midway through the summer, a group of researchers from Scotland published a paper on similar research. In light of this, Beussman and Eckmann altered and expanded the scope of their project slightly, and are hoping to get a paper submitted before someone else has the chance to publish on the topic.
Eckmann is majoring in chemistry and also pursuing a concentration in biomedical studies. This fall he will continue researching with Beussman, and he plans to pursue medical school after graduation. Beussman plans to continue research in fiber analysis, expanding from white cotton fibers to those found in blue jeans, polyester, and even plastics.