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The Analysis of Trace Forensic Evidence Using Isotope Ratio Mass Spectrometry: Differentiating Fibers

NCJ Number
Douglas J. Beussman
Date Published
October 2017
46 pages
This study examined whether isotope ratio mass spectrometry (IRMS) can be used to add an additional level of information about a fiber that may enable two fibers to be compared for common characteristics.
Current methods can determine the chemical composition and color of a fiber as well as its physical characteristics, but unless the fiber contains DNA, there is no way to compare a fiber found at a crime scene with fibers found in a suspect's possession. Based on the results of this study, IRMS appears to be a potentially useful forensic technique for the analysis and differentiation of a wide range of fiber types, both natural and synthetic. Fibers of the same chemical composition but from different manufacturers or production batches can be differentiated using IRMS. Fibers from the same clothing item have statistically indistinguishable isotope ratio values, provided that the fibers are sampled from the same region of cloth. Thus, fibers from a crime scene and those from a different source will likely be able to be distinguished from one another. A variety of types of non-colored fibers, including cotton, wool, silk, and a number of synthetics were analyzed. Between 10 mg and 200 mg of fiber was used for each analysis with an elemental analyzer used to measure the 13Carbon and 15Nitrogen isotope ratios. A high temperature conversion elemental analyzer was used for the analysis of 2Hydrogen and 18Oxygen isotope ratios. Using a combination of all four isotopes, all fibers were able to be distinguished from other fibers of the same chemical composition but from different manufacturers, or from the same manufacturer but from different years. 27 tables, 11 figures, and 23 references