NCJRS OFFICE OF JUSTICE PROGRAMS ~ N ATIONAL CRIMINAL JUSTICE REFERENCE SERVICE QJA BJS N/J OJJ[l> OVC SMART ",iiiii~ The author(s) shown below used Federal funding provided by the U.S. Department of Justice to prepare the following resource: Document Title: The Analysis of Trace Forensic Evidence Using Isotope Ratio Mass Spectrometry: Differentiating Fibers Author(s): Douglas J. Beussman Document Number: 251209 Date Received: October 2017 Award Number: 2012-DN-BX-K020 This resource has not been published by the U.S. Department of Justice. This resource is being made publically available through the Office of Justice Programs’ National Criminal Justice Reference Service. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. Department of Justice. Report Title: The Analysis of Trace Forensic Evidence Using Isotope Ratio Mass Spectrometry: Differentiating Fibers Award Number: 2012-DN-BX-K020 Author(s): Douglas J. Beussman Location: St. Olaf College 1520 St. Olaf Ave. Northfield, MN 55057 1 This resource was prepared by the author(s) using Federal funds provided by the U.S. Department of Justice. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. Department of Justice Abstract Fibers are often found at crime scenes and current methods can determine the chemical composition and color of the fiber as well as physical characteristics. 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. This study aims to determine if isotope ratio mass spectrometry (IRMS) can be used to add an additional level of information about a fiber, potentially allowing two fibers to be compared for common characteristics. This could provide additional evidence that two fibers may have come from the same original source. Between 10 µg and 200 µg of fiber was used for each analysis with an elemental analyzer used to measure the 13Carbon and 15Nitrogen isotope ratios, or a high temperature conversion elemental analyzer for the analysis of 2Hydrogen and 18Oxygen isotope ratios. A variety of types of non-colored fibers, including cotton, wool, silk, and a number of different synthetics were analyzed. 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. Homogeneity within a commercial shirt was studied to determine if sampling location is important when comparing two different fibers. All fibers from the same clothing panel were found to be isotopically homogenous, but depending on manufacturer some shirts were found to have different isotope ratios in the shirt body compared to shirt sleeves. This could be the result of different shirt panels being cut from different bolts of cloth and then sewn together. White and colored fibers were compared to determine if the coloring has an effect on the isotope ratio. The manner in which the shirt was constructed was found to determine the effect of color on the fiber isotope ratios. For shirts that were constructed of distinct fibers of different colors, differences in the isotope ratios of differently colored fibers were observed. For shirts woven from a single thread, with different regions colored differently, fibers of different colors exhibited consistent isotope ratio values. Thus, the fiber material itself, and not the coloring, appear to control the isotope ratios. Fibers were stained with blood, grass, or dirt to investigate whether common stains can change the isotope ratio values. Grass and dirt stains were not found to result in a significant change in isotope ratio values likely because these are surface stains. Blood stained fibers, however, did exhibit a change in isotope ratio values, most likely because blood can penetrate the fiber. Since fibers are routinely analyzed for DNA, pre- and post-DNA processed fibers were compared to determine if isotope ratio analysis can still be used after fibers have been treated to extract any DNA that might be present. Carbon and nitrogen isotope ratios were not found to change, but in one-third of the fiber samples, oxygen and/or hydrogen values were affected by the DNA processing protocol. Based on the results of this study, isotope ratio mass spectrometry 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 whereas 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. 2 This resource was prepared by the author(s) using Federal funds provided by the U.S. Department of Justice. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. Department of Justice Table of Contents Executive Summary ……………………………………………………………………..……… 4 1. Introduction ……………………………………………………………………………….. 14 2. Methods ……………………………………………………………………………………. 15 2.A. Materials ………………………………………………………………………...… 15 2.B. 13C and 15N isotope analysis ………………………………………………...……. 15 2.C. 2H and 18O isotope analysis …………………………………………………...…... 15 2.D. Dyed and Bleached T-Shirt Analysis …………………………………………...… 16 2.E. Stain Analysis ………………………………………………………...…………… 16 2.F. DNA Processing Analysis ……………………………………………...…………. 16 2.G. Environmental Exposure Analysis …………………………………………………17 2.H. Statistical Analysis ………………………………………………………...……… 17 3. Results …………………………………………………………………………………...…. 18 3.A. White Cotton ……………………………………………………...………………. 18 3.A.1. Cotton from Different Sources …………………………..……………… 18 3.A.2. T-shirt Homogeneity ……………………………………..……………....20 3.A.3. T-shirts of Identical Origins ………………………………..…………… 21 3.A.4. Stitching vs. Cloth …………………………………………..…………... 21 3.A.5. Cotton from Different Years/Manufacturing Processes ……...…………. 22 3.B. Colored Cotton …………………………………………………………..………... 24 3.B.1. Colored Shirts …………………………………………………...………. 24 3.B.2. Dyed Shirts ………………………………………………………..…….. 27 3.B.3. Bleached Shirts ………………………………………….………………. 28 3.B.4. Worn Jeans Material ……………………………………….……………. 30 3.C. Other Natural Fibers …………………………………………………….………… 31 3.C.1. Wool …………………………………………………………………….. 31 3.C.2. Silk ……………………………………………………………………… 33 3.D. Synthetics ………………………………………………………………................. 34 3.E. Carpet ……………………………………………………………………...……… 35 3.F. Effect of Surface Stains ……………………………………………………...……. 36 3.G. Effect of Blood Stains ………………………………………………………..…… 38 3.H. Effect of DNA Extraction ……………………………………………………..….. 38 3.I. Effect of Environmental Exposure ……………………………………………..….. 39 3.J. Sample Size Analysis …………………………………………………………..….. 39 4. Conclusions ………………………………………………………………………...………. 41 5. References …………………………………………………………………………..……… 42 6. Dissemination of Research Findings ……………………………………………….……… 44 3 This resource was prepared by the author(s) using Federal funds provided by the U.S. Department of Justice. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. Department of Justice Executive Summary Synopsis of the Problem Fibers are of special importance to forensic analysis due to their prevalence at crime scenes. Therefore, it is important to analyze these materials for any differentiating characteristics that could be used to connect a suspect with a fiber found at a crime scene, or to exclude potential suspects. In the past, various methods have been used to identify and analyze fibers. Infrared spectroscopy can discriminate different types of fibers (cotton, silk, polyester, etc.) with similar appearances. Further Infrared and Raman spectroscopy analysis can differentiate fibers with different dyes and contaminants. However, these techniques are unable to distinguish between different fibers of the same material and color (i.e. two different white cotton fibers). Therefore, without the differentiating chemical and visible characteristics (such as color, texture, etc.) that allow for the differentiation of fibers, different methods need to be used to distinguish between different fiber samples. Purpose IRMS can differentiate between these cotton samples because the percent abundances of given elements (i.e. the ratios of heavy to light isotopes) differ under various conditions.8 Variations in isotope abundances of light elements are caused by processes that favor one isotope over another, a process called fractionation. Carbon isotope variations in plants reflect the isotope composition of the reactant (CO2) in the ambient atmosphere around the plant, the diffusional isotope fractionation of CO2 into the plant, and a large biochemical/enzymatic isotope fractionation. The oxygen and hydrogen isotope composition of plant tissues typically have strong geographic correlations, reflecting largely geographic patterns of isotope ratios of source water to the plant (typically in the form of precipitation in which the isotope composition is affected by fractionation associated with progressive