The factors influencing the identification of the chronological intersecting sequence between ink and toner

Identifying the formation time of a document is a problem forensic document examiners often face. It is understood that intersections with different intersecting sequences made by the same laser printer and the same gel pen are distinct from each other under coaxial light, and the appearance of an oil film or bright metallic marks in the regions of interest can be used as the basis to identify that the ink is above the toner. However, the characteristics of intersections may be influenced by a number of factors. Studying the characteristics of the intersections formed by laser-printed graphics and handwriting strokes made with a gel pen in different intersecting sequences can help us determine the formation sequence of each part on a questioned document. In this manuscript, samples were made using three pen types and two laser printers. A Leica stereo microscope M205A was used to capture the apparent morphology of the intersections. Microspectrophotometry spectra of all intersections were collected in reflectance mode using a video spectral comparator 6000 (VSC6000), and the resultant data were measured and analyzed in Statistical Product and Service Solutions 26.0 (SPSS). The results showed that 92.5% absolute accuracy was achieved from blind tests, and the intersecting sequence can be determined using the optical data of the intersections with an accuracy of up to 97.5% through discriminant analysis under ideal conditions.