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

Muhammad N. M. Asri, Nor A. M. Noor, Wan N. S. M. Desa, Dzulki ee Ismail


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
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.


Forensic Science, Questioned Document, Hyperspectral Imaging, Principal Component Analysis, Gel Pen Inks.

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