A New and Practical Way to Reveal Latent Fingerprints on ATM Thermal Papers as a Detection Clue at Crime Scenes

Thermal paper is a kind of paper with special coating that allows printing without ink. The result of applying heat (via a thermal printer) to the coating on thermal paper is a clear image without the need for ink, toner or ribbon. This type of technology is used in various sectors. One of the ways fingerprints appear on thermal paper is to use chemical reactants such as Ninhydrin solution but the revealed fingerprint color does not usually show fingerprint features, therefore; in this way, fingerprints can not be detected. In this study, the use of Ninhydrin with Acrylamide in different ratios for developing hidden fingerprints in thermal papers was tested. The results showed that using a concentration of 0.020-0.060 g / ml Acrylamide in Ninhydrin solution with the appearance of fingerprints and the necessary separation of indicators after testing with thermal paper while creating a suitable background, separation and appearance of fingerprints work and fingerprints were identified with sharp resolution. Minutiae indicators (fingerprints) using an automated fingerprint recognition system (AFIS), detected between 59-87 points of the indicators. This method can be used as an alternative corrective method for detecting hidden fingerprints on paper and the heat paper should be used without any damage to the samples and with high quality, and while reducing costs, the efficiency of the Ninhydrin method should also help to increase the appearance of fingerprints.