Raman spectroscopy for forensic analysis of inks in questioned documents

The methods for perpetrating forgery and alteration of documents are becoming increasingly more sophisticated. Forensic examinations of questioned documents routinely involve physical and chemical analysis of inks. Raman spectroscopy is a very attractive technique for ink analysis because it combines chemical selectivity with ease and fast analysis and it does not require sample preparation nor leads to destruction of the evidence. However, some limitations of this technique include low sensitivity and the overwhelming phenomenon of fluorescence, which can be solved by resonance Raman spectroscopy and surface-enhanced Raman spectroscopy. This article aims to demonstrate the great potential of the Raman-based techniques by providing an overview of their application to forensic examinations of ink evidence from pens and printers. Moreover, it is also addressed the chemistry of ink-paper interactions and the problematic of intersecting lines.