Hofstetter, Oliver D.
Ph.D. (Doctor of Philosophy)
Department of Chemistry and Biochemistry
Latent fingermarks are among the most common forms of physical evidence left at crime scenes. Being composed largely of eccrine and sebaceous secretions, they are typically invisible unless they are treated with, e.g., powders or cyanoacrylate fumes. Drawbacks to these and other commonly used methods, however, may include limited substrate compatibility, safety hazards, inability to detect older marks, and the need for expensive instrumentation and expert practitioners. Fingermarks on curved, reflective, patterned, or luminescent substrates are particularly challenging to image with most common techniques. After treatment, fingermarks on such difficult substrates may be transferred to, or “lifted” by, flexible adhesives, although this separate step introduces an additional juncture at which ridge detail may be lost or destroyed. Furthermore, most latent fingermark detection techniques leave a visible record of their application, making them unsuitable for covert operations.This dissertation describes the development of several novel types of devices for the lifting and visualization of latent fingermarks. These “lifters” contain either pH indicators or amine-reactive reagents that change their spectral properties upon contact with skin secretions in fingermark residue, thus allowing the visualization of ridge characteristics on the lifters themselves. In particular, the pH indicators phenol red and pyranine, as well as the amine-reactive reagent fluorescamine, were found to yield high-contrast, detailed ridge patterns upon fingermark contact when adsorbed to commercially available synthetic membranes or incorporated into natural or synthetic polymeric matrices. After the selection of appropriate device components, preparation procedures were optimized in order to improve each type of lifter’s sensitivity to latent fingermarks. This was followed by small-scale evaluations, in which the reactive lifters were found to exhibit several potential advantages over existing fingermark detection methods, including ease of use, low-cost imaging, compatibility with a wide variety of substrate types, lack of safety hazards, and lack of detectable traces after application. Therefore, these lifters, possibly after further optimization of preparation and storage conditions, promise to be useful for routine forensic applications, especially in covert operations.
Mlakar, Andrei Gregory, "Development of pH-Sensitive and Amine-Reactive Lifters for the Detection of Latent Fingermarks" (2022). Graduate Research Theses & Dissertations. 7456.
Northern Illinois University
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