Enhancing the evidentiary value of textile fibers with a combination of fluorescence microscopy and micro spectrophotometry

This proposal addresses current research gaps identified by forensic practitioners for the application of fluorescence microscopy to forensic fiber examination. The Trace Materials subcommittee of the Organization of Scientific Area Committees for Forensic Science have identified four specific research needs: (a) Determine wavelength ranges that provide the highest discriminating capabilities among fibers commonly encountered in forensic casework; (b) Reduce the photobleaching of fibers during fluorescence microscopy and micro-spectrophotometry analysis; (c) Identify the effects of exposing fibers to chemicals used in collecting or preserving evidence for other forensic disciplines; and (d) Identify the existence of environmental contaminants with the potential to alter the fluorescence properties of textile material.

This proposal will engage each objective through the following means: (a) Fibers determined as the most commonly encountered will be analyzed under different wavelength ranges. The spectra and images collected will be statistically reviewed to determine which wavelengths provide the greatest discriminating power for each fiber type; (b) Photobleaching studies will be conducted to determine the exposure duration each fiber type can withstand from the different wavelength ranges before significant degradation, and to determine how to reduce the photobleaching; (c) Forensic chemical tests for fingermark development, bodily fluid screening, and chemical residue screening will be applied to textile samples. Fibers from treated samples will be analyzed to determine how the spectra and images are altered by the treatments; (d) environmental contaminants, including urban dust and pollen, tobacco smoke, detergents, and food stains, will be systematically applied to textile samples. Fibers from treated samples will again be analyzed to determine how the spectra and images are altered by the environment contaminants.

Successful completion of the proposed research will provide physical evidence analysts with a statistically valid and tested methodology for comparing physical evidence items. The methodology will be tested across multiple color-fiber type combinations frequently encountered in forensic science. Image and spectral databases for each fiber type will be compiled in downloadable files and made available to the Forensic Science community at the web page of the National Center for Forensic Science. The statistical packages for methods implemented in the project will be made publicly available on the investigators’ webpages for direct implementation of forensic scientists. By supplying the findings in easily accessible online databases, this research will provide the forensic science community a route to quickly implement the developed tools and improve the quality of the discipline. CA/NCF