Department/unit chief - Forensic Department "Fingerprints", IRCGN
Thermal papers, such as printed receipts or lottery tickets, are omnipresent in our everyday life. Although they are considered as semi-porous substrates, they can be very difficult to deal with when looking for latent fingerprints, because of their thermosensibility.
The aim of this study was to develop a revelation sequence which combines at best the adequate techniques of detection, so as to maximize the likelihood to reveal all the latent fingerprints present on these substrates.
Particularly, steps of thermal revelation and whitening have been introduced and optimized. The different revelation methods have been tested and compared on test substrates: the optimal temperature for revelation on the glossy side has been determined, black magnetic powder has been compared to LumicyanoTM and the importance of the whitening step on the quality of the prints revealed with ninhydrin or 1,2-indanedione/ZnCl2 has been demonstrated.
The results of these preliminary tests have enabled the development of three revelation sequences, which have been compared to the sequence currently used in the Gendarmerie’s laboratories. One of these sequences, incorporating six steps, provided the best results during pseudo-operational comparative trials.
latent fingerprint, Thermal paper, Whitening