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.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this paper is to review the scientific literature from August 2007 to July 2010. The review is focused on more than 420 published papers. The review will not cover information coming from international meetings available only in abstract form.
[Show abstract][Hide abstract] ABSTRACT: In current casework, most post-cyanoacrylate stains rely on luminescence emission in the visible region (400-700 nm). While traditional stains such as rhodamine 6G work well under most circumstances, some surfaces may generate background luminescence under the same conditions. Detection in the near-infrared region (NIR > 700 nm) has shown to be effective in minimizing the interferences from such surfaces. The laser dye styryl 11 generated strongly luminescent fingermarks when applied after cyanoacrylate fuming on all surfaces tested. When compared to rhodamine 6G, the dye was superior only when viewed in the NIR. Styryl 11 was subsequently combined with rhodamine 6G, and the mixed stain formulation (named StaR 11 by the authors) induced stronger luminescence compared with styryl 11 alone with an ability to visualize in both the visible and NIR regions. Reliable and consistent results were obtained when using either styryl 11 alone or the STaR 11 mixture. The enhancement achieved did not otherwise vary depending on the source of the fingermark secretions. With visualization possible in both the visible and NIR regions, the styryl 11/rhodamine 6G mixture showed significant potential as a post-cyanoacrylate stain.
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