Improving the confidence of “questioned versus known” fiber comparisons using microspectrophotometry and chemometrics

Microspectrophotometry followed by chemometric data analysis was conducted on pairs of visually similar blue acrylic fibers, simulating the “questioned versus known” scenarios often encountered in forensic casework. The relative similarity or dissimilarity of each pair was determined by employing principal component analysis, discriminant analysis and Fisher’s exact test. Comparison of fibers from within each set resulted in a correct inclusion result in 10 out of 11 scenarios, with the one false exclusion attributed to a lack of reproducibility in the spectra. Comparison of fibers from different sets resulted in a correct exclusion result in 108 of 110 scenarios, with two sets that shared identical dye combinations being indistinguishable. Although the presented methods are not infallible, they may nonetheless provide a path forward for forensic fiber examiners that has a more scientifically rigorous basis on which to support their findings in a court of law