DEVELOPMENT OF LATENT FRICTION RIDGE PRINTS

摘要

Apparatus to produce a spatially and temporally uniform heat source is described and this is used to visualize latent fingerprints deposited onto thermal paper by raising the temperature of the paper. Results show an improvement over previous techniques, particularly when fingerprint deposits are aged or the developed fingerprints faint; visualization being enhanced by the use of an LED light source. An investigation of the components in fingerprint sweat likely to affect the solubility and hence colour change of the dye present in the thermal paper has shown that polar protic solvents able to donate a proton are favoured and a polar amino acid found commonly in eccrine fingerprint sweat (lysine) has been shown able to produce the desired colour change. Aged fingerprint deposits on thermal paper from a variety of sources up to four years old have been visualized with this technique.

主权项

1. Apparatus to develop latent friction ridge prints deposited onto thermal paper, the apparatus comprising:
a heat source for spatially and temporally heating a thermal paper sample uniformly; an electro c radiation source for illuminating the sample during heating; and a light detector for automatically detecting developing prints,whereby heating of the sample can be terminated following appearance of a print to protect the sample from overdevelopment.