Near infrared imaging for the improved detection of fingermarks on difficult surfaces

Abstract

The near infrared spectral region offers advantages over the visible region in the detection of latent fingermarks due to increased contrast and decreased background luminescence. In this work, a chemical imaging system was used to image latent fingermarks in the near-infrared (NIR) region. A variety of porous, non-porous and semi-porous surfaces were tested using standard chemical and physical enhancement techniques. NIR dyes were also used to enhance latent marks. Both absorption and luminescence properties of the treated marks were examined over the spectral range 650–1100 nm. Significant NIR absorption was found for ninhydrin, iodine/benzoflavone, physical developer, and powdering. NIR luminescence emission was found for DFO, ninhydrin with zinc salt post treatment, 1,2-indanedione and genipin. Significant NIR luminescence emission was found for cyanoacrylate fuming followed by staining with NIR dyes. In addition, metal oxide powders coated with NIR dyes were able to enhance fingermarks on a patterned and highly luminescent surface.

Keywords:

• fingermark
• fingerprint
• near-infrared
• imaging, chemical imaging
• luminescence

Acknowledgements

Samples of Genipin-developed fingermarks were supplied by Simon Lewis of Curtin University of Technology and Jade Lyons of Deakin University. Styryl dye samples were provided by Milutin Stoilovic, Australian Federal Police.