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.
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ABSTRACT: This study investigated the application of chemical imaging to the detection of latent fingerprints using the Condor macroscopic chemical imaging system (ChemImage Corp., Pittsburgh, USA). Methods were developed and optimised for the visualisation of untreated latent fingerprints and fingerprints processed with DFO, ninhydrin, cyanoacrylate, and cyanoacrylate plus rhodamine 6G stain. The results obtained with chemical imaging were compared to the detection achieved using conventional imaging techniques. The Condor significantly improved the detection of many prints, especially those that might be considered poor quality or borderline prints. Prints on newspaper treated with ninhydrin and DFO, and prints on white and yellow paper treated with ninhydrin, benefited the most from chemical imaging detection. In many cases, fingerprints undetectable using conventional imaging techniques could be visualised with chemical imaging. Ridge detail from untreated prints on yellow paper was also detected using the Condor. When prints of high quality were examined, both detection techniques produced quality results. The results of this project demonstrate that chemical imaging offers advantages over conventional visualisation techniques when examining latent fingerprints, especially those that would be considered difficult, such as weak prints or prints on surfaces that produce highly luminescent backgrounds. Standard testing procedures for the detection and enhancement of fingerprints by chemical imaging are presented and discussed.Forensic Science International 06/2005; 150(1):33-51. · 2.31 Impact Factor
- Journal of Forensic Science. 01/2004; 49(2):255-257.
Article: Principal Component Analysis[show abstract] [hide abstract]
ABSTRACT: This site provides an introduction to principal component analysis, beginning with a glossary of important terms before taking the reader through the process of completing a principal component analysis. One limitation to the site is its reliance on Minitab and SPSS for calculations. Users without access to these programs can reproduce the calculations using other software packages, such as the freeware program R. Prior knowledge of basic statistics is assumed; thus, the site is most appropriate for advanced undergraduates and graduate students.01/2010;