Hanging by a Thread: Enhancing the Forensic Value of Dyed Cotton Trace Evidence through the Application of Novel Techniques in Fiber Discrimination
This thesis examines the capability of current techniques in fiber classification such as UV-visible microspectrophotometry (MSP) (for dye in situ and/or extracted) to discriminate between fib ers from sources known to be different. When these methods fail to adequately distinguish the fibers, novel alternative techniques - such as pulsed pumped laser-induced fluorescence spectroscopy (LIF) and liquid chromatography-mass spectrometry (LC-MS) - are utilized to provide definitive forensic evidence.
The FBI Dye Extraction Classification And Chromatography Schemes: Forensic Fiber Examination Guidelines provides the methodology used by the majority of crime labs across the United States (1). In the case of cotton fibers -- the most frequently encountered fiber form of trace evidence-- the scheme fails to produce adequate evidence to establish a questioned/known match (10). In fact, in many criminal investigations the protocols indicate a false positive association (14). New methods of discriminating between dyed cotton fibers are needed to promote the evidential value of trace fibers.
The preliminary data confirm unique identification of all the fibers using these enhanced investigative tests, a task not possible by conventional analysis alone. Analysis by multiple techniques greatly enhances the probative value of trace fibers in criminal investigations by providing fiber discrimination at a higher degree of certainty. This study demonstrates the benefit of applying new techniques in the forensic investigation of fibers to reduce the chance of an incidental match. Sixty percent discrimination was achieved by employing current protocols; discrimination was improved to one-hundred percent by applying the methods outlined in this paper. The application of liquid chromatography-mass spectrometry (LC-MS) and ultraviolet fluorescence spectroscopy to the analysis of cotton fibers is shown in this paper to greatly increase their evidentiary value by providing highly specific chemical and structural information about the dyes and brighteners.
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Bachelor of Science (B.S.)
College of Arts and Sciences
Arts and Sciences -- Dissertations, Academic; Dissertations, Academic -- Arts and Sciences; Chemistry, Forensic; Forensic sciences; Microspectrophotometry; Textile fibers -- Analysis
Length of Campus-only Access
Honors in the Major Thesis
Russo, Rachel, "Hanging by a Thread: Enhancing the Forensic Value of Dyed Cotton Trace Evidence through the Application of Novel Techniques in Fiber Discrimination" (2005). HIM 1990-2015. 477.