Using Vacuum Metal Deposition to Detect Latent Fingermarks on Thermal Paper: A Pseudo-operational Trial

This work presents a pseudo-operational study on thermal paper for the detection of latent fingermarks with vacuum metal deposition (VMD) and the amino acid sensitive reagents, 1,2-indanedione and ninhydrin, on 120 thermal receipts. Two sequential treatments were employed on both sides of the paper (thermal and non-thermal side) and fingermarks developed by each process were counted and imaged. Both sequences started with the use of UV imaging, process A then continued with VMD gold/zinc and silver followed by the amino acid sensitive reagents whereas process B only utilised the amino acid sensitive reagents. Both processes detected a similar number of marks on the thermal side by the end of the sequence. The use of amino acid sensitive reagents in sequence after VMD enhancement (Process A) increases the detection rate on the thermal side by approximately a factor of two and a half. VMD did not further visualise all of the marks detected by UV; however, this was the case for the amino acid sensitive reagents. The use of VMD can be suitable for the detection of fingermarks on thermal paper in cases where the text needs to be retained; however, the use of 1,2-indanedione and ninhydrin, in sequence with VMD or alone, will detect a higher number of marks.