**4.10. Forensic document examination**

IR spectroscopy and X-ray diffraction techniques may quickly determine the types and rates of molecules in a paper structure without causing damage to or installing contact with examined materials. These two techniques enable the detection of variations in the structure brought about by different processing parameters, manufacturing conditions and formulation of additives [63]. The differentiation of photocopy documents and documents published in printer toners may be discriminated by reflection-absorption IR spectroscopy [64]. In a study performed by Merrill et al., many toners of photocopies and printers have different IR spectrums. When these differences are recorded in a system and compared with a spectral library, it is possible to identify the make and model of a copy machine or obtain a list of machines that use toner with comparable spectral characteristics [65]. It has been demonstrated that places with unreadable eyes in burned documents may be read using an IRT technique [16, 48]. In studies regarding inks and paints, it was determined that individual inks and paints have different spectral characteristics. If there was a spectral library of inks and paints, a questioned document may be examined based on the pen type used in the construction of a document or spuriousness of a picture or document [66–69]. Erasures and changes on the documents may be determined using technologies based on IR techniques [16, 67]. Technolo‐ gies such as VSC 2000, VSCHR, VSC 5000, VSC 6000, Forensic XP 4010 and Forensic XP 4010 D have been used for forensic document examination [67]. One study investigated the detection of writing on fabric, in which three different black pens (fountain pen, ballpoint pen and permanent marker) were signed on three different black fabrics. The researchers reported that these invisible signs became visible using IR imaging. They determined that "fountain pen ink could be visualized using IR light less effectively than the permanent inks but was recorded on considerably more occasions than the ball point pen" [39]. During this examina‐ tion, a lack of destruction on the examined document, facilities for simultaneously analysing all substances on the entire material and the repeatability of the method were defined as advantages of these techniques [47].
