Non-destructive techniques that can either discriminate between similar fibers or match a known to a questioned fiber - and still preserve the physical integrity of the fibers for further court examination - are highly valuable in forensic science. When fibers cannot be discriminated by non-destructive tests, the next reasonable step is to extract the questioned and known fibers for dye analysis with a more selective technique. Unfortunately, dye extraction destroys the evidence and the possibility for fiber court examination no longer exists. We investigate the total fluorescence of fibers. In addition to the contribution of the textile dye (or dyes) to the fluorescence spectrum of the fiber, we examine the contribution of intrinsic fluorescence impurities � i.e. impurities imbedded into the fibers during fabrication of garments - as a reproducible source of fiber comparison. This presentation explores the application of excitation-emission fluorescence data as a three-dimensional matrix for comparison of single-fibers. Fibers treated with a variety of dyes that are indistinguishable by eye and with similar absorbance spectra were used for purposes of identification. Excitation-emission matrices (EEMs) were directly recorded from single fibers with no need of dye extraction. By accounting for the variance of the EEM spectra at different regions along the length of the fiber a training set is obtained that can be used as the basis for principal component cluster analysis. Statistical figures of merit for correct identification of fiber dyes are described so that identification of single evidential fibers to other single fibers, threads, or bulk materials may be accomplished with 99% confidence.

Fiber discrimination based on fluorescence excitation emission matrices and cluster analysis

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.