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Abstract
Tracing a printed document back to its device is an important issue in forensic examinations of questioned documents. Raman spectroscopy is a resourceful technique for document analysis since it provides molecular information of many inks’ components, the type of paper has no effect on the results, and it is a non-destructive technique. Research studies utilise Raman instruments that have a greater potential than the ones used by many law enforcement institutions, which are adapted for routine casework. The potential and limitations were investigated of one Raman instrument, which was especially designed for document casework with regards to the complex discrimination of samples printed by different inkjet printers from the same manufacturer. The results showed low signals for most of the samples, especially black lines, due to fluorescence. To eliminate this, surface-enhanced Raman spectroscopy (SERS) was performed. The surface treatment method with a silver colloid was studied and optimised to be a less invasive method. SERS spectra resulted in more intense and well-shaped bands but the same profile, typical of copper phthalocyanine derivatives, overwhelmed the entire spectra for blue and black ink lines. Notwithstanding, closer examination revealed smaller spectral differences, which allowed discrimination of the samples into two groups: samples printed by the Deskjet models and samples printed by professional models such as Photosmart, Business and Officejet.