Defense Date
2024
Document Type
Directed Research Project
First Advisor
Mary Keehan, M.S.
Second Advisor
Nicole Palmer, M.S.
Third Advisor
Eric Hazelrigg, M.S.
Abstract
Cotton, the most common natural fiber, has numerous uses in the textile industry. This fiber type is ubiquitous in forensic casework due to its prevalence, particularly in blue jeans. The abundance of blue cotton in society and its limited variations in features can diminish the probative value of its presence on items of evidence. While a pair of blue jeans may be constructed with a combination of natural and manufactured fibers, the most likely fiber type to be transferred between sources is cotton. In this study, a comprehensive analytical approach to blue jean fiber analysis was explored to determine if blue cotton fibers from different blue jean sources could be reliably discriminated. The degree of differentiation was determined through the calculation of discrimination power for each individual technique, as well as additively at each step of the analytical scheme. Finally, the discrimination power of the analytical scheme as a whole was calculated. A combination of brightfield (BF) comparison microscopy, polarized light microscopy (PLM), fluorescence, ultraviolet-visible microspectrophotometry (UV-Vis MSP), and microchemical testing were employed to determine the fiber discrimination power achieved throughout the scheme. Examiner bias was mitigated by randomizing and renumbering all fabric samples prior to conducting examinations. The analytical procedures were assessed with two duplicated samples. Additionally, verifications of all sample discriminations using PLM were performed by a qualified practitioner. Given the variability in fabric dyeing, finishing processes, and deposits from wear and laundering, the goal of the project was to reassess the evidentiary value of blue jean fiber examinations to determine if a low significance currently assigned to common source comparisons is appropriate. After comparison of fibers from 64 pairs of jeans (including two duplicated pairs), the resulting independent discrimination powers for BF/PLM, fluorescence, UV-Vis MSP, and microchemical analysis were 48%, 48%, 9%, and 6%, respectively. The comprehensive fiber discrimination power achieved was 70%. Incorporating fabric examination as the first step in the scheme yielded a combined discrimination power of 99%. The independent fabric analysis discrimination power was 98%. These results indicate that blue jean cotton common source examinations do not possess the potential to be assigned a higher degree of association than previously held. However, if the known and questioned fabrics are also compared, then a higher degree of association should be considered despite being composed of blue cotton fibers.
Rights
© The Author(s)
Is Part Of
VCU Master of Science in Forensic Science Directed Research Projects
Date of Submission
4-29-2024