Using Raman spectroscopy to solve crime: inks, questioned documents and fraud

Raman microscopy is becoming a tool of major importance in forensic analysis, particularly of drugs and explosives. It is a non-invasive, non-destructive chemical probe allowing samples to be examined in their entirety without any preparation. This paper demonstrates the use of the technique as a general tool for inks analysis. Furthermore, it addresses two important issues that historically have been extremely difficult for the professional document examiner, namely, comparison of black ballpoint inks and the chronological sequencing of crossed ink lines. We show that Raman can successfully distinguish between a representative sample of commercially available black ballpoint inks. This data has been converted into a database for future reference. A method for chronological sequencing of crossed ink lines has been developed using confocal Raman microscopy. Case study work has shown the feasibility of this approach.