NIR luminescence for the inspection of thermal paper: a novel tool for fingermarks detection

The near infrared (NIR) spectral region could offer advantages over the visible region in the detection of latent fingermarks due to the enhanced contrast between the background and the print. In this present paper, this spectral range of the electromagnetic spectrum was explored in order to study the possibility to make feasible the inspection of forensic evidences when the substrate is represented by the thermal paper, which is one of the most extensively used porous surfaces for printing receipts. We successfully applied the method to thermal paper treated with several kinds of amino acid sensitive reagents. We demonstrated that, even if the treatments could cause a dark stain over the latent fingermarks, by exploiting the luminescence of thermal paper in the NIR window we were able to create a contrast otherwise impossible in the visible region.