A chronological overview of analytical techniques in forensic identification of printing toners

This review embodies a comprehensive study pertaining to forensic examination of photocopied documents. A critical discussion on the trends, advances of analytical techniques implemented in the past four decades, and their respective edge over each other has been explicitly presented in the study. The field of interest has witnessed pronounced development in the examination procedures, particularly in the methodology and sample preparation. Analytical methods including spectroscopic, microscopic, and chromatographic techniques for the examination of printing toner have been variedly reported. Furthermore, studies focusing on the physical and optical examination of toner and printed document have also been discussed. The majority of studies have shown the efficacy of ATR-FTIR in identifying the binders present in toners. Raman spectroscopy has been largely employed to identify the type of pigment used in the printed sample. Techniques like SEM-EDX, XRF, LIBS, LA-ICPMS, etc. have been used for the elemental profiling of the toners. Recent literature shows the advent of techniques that are non-destructive, require nil to minimal sample preparation, and sustain the integrity of the sample as evidence. Another significant development is the use of data fusion techniques and chemometric methods to enhance the discrimination and identification of the sample. This is plausibly the only detailed review that features all the techniques that have ever been used for the forensic investigation of photocopiers and their toners.