Forensic Analysis of Gel Pen Inks using Hyperspectral Imaging coupled with Chemometric Procedures

Abstract Forensic examination of inks on questioned documents has become an important practice and the law enforcement agencies rely heavily on these techniques during criminal investigations. Although nowadays there are a variety of methodologies focused on the analysis of inks, the combination of non-destructive nature of Hyperspectral Imaging (HSI) coupled with the multivariate chemometric technique has received little attention. In this study, forty-five (n = 45) gel pen inks of three different colours i.e. blue, red and black of five different brands were analysed using HSI with the idea of classifying them according to the brand. In terms of discriminating similar coloured components between samples, this was achievable only on the basis of the % reflectance spectra. However, arguably, there was sufficient evidence to suggest that it may be possible to discriminate the samples using chemometric of Principal Component Analysis (PCA). A 2-D score plot from PCA analysis was enough to characterise the samples into five clusters. The synergy of complementary information provided by PCA narrows matching possibilities (in terms of classification) for forensic investigations involving ink analysis.