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

Abstract

Forensic examination of inks on questioned documents has becomean important practice and the law enforcement agencies rely heavilyon these techniques during criminal investigations. Although nowadaysthere are a variety of methodologies focused on the analysis of inks, thecombination of non-destructive nature of Hyperspectral Imaging (HSI)coupled with the multivariate chemometric technique has received littleattention.In this study, forty-five (n = 45) gel pen inks of three different coloursi.e. blue, red and black of five different brands were analysed usingHSI with the idea of classifying them according to the brand.In terms of discriminating similar coloured components betweensamples, this was achievable only on the basis of the % reflectancespectra. However, arguably, there was sufficient evidence to suggestthat it may be possible to discriminate the samples using chemometricof Principal Component Analysis (PCA). A 2-D score plot from PCAanalysis was enough to characterise the samples into five clusters.The synergy of complementary information provided by PCA narrowsmatching possibilities (in terms of classification) for forensic investigationsinvolving ink analysis.