A rapid method to detect dried saliva stains swabbed from human skin using fluorescence spectroscopy |
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Authors: | Soukos N S Crowley K Bamberg M P Gillies R Doukas A G Evans R Kollias N |
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Institution: | Wellman Laboratories of Photomedicine, Department of Dermatology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA. soukos@helix.mgh.harvard.edu |
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Abstract: | Saliva on skin is important in forensic trace evidence. If areas where saliva is present can be outlined, this may lead to DNA analysis and identification. This study describes a rapid and non-destructive method to detect dried saliva on the surface of the skin by fluorescence spectroscopy. Eighty-two volunteers deposited samples of their own saliva on the skin of their ventral forearm. A control sample of water was deposited at three different sites on the contralateral arm. Saliva and water control were then allowed to air-dry. Swab samples were taken from dried saliva and control sites and were dissolved in 0.1M KCl solution. Emission spectra were obtained from the solution and were characterized by a principal maximum at 345-355nm with excitation at 282nm. The fluorescence emission intensity was greater than background readings obtained from the control swab site in 80 of 82 volunteers (approximately 97.6%). The fluorescence profile of saliva samples were similar to those obtained from aqueous samples of pure amylase and tryptophan, an endogenous fluorophore in alpha-amylase. The presence of an emission peak at 345-355nm with excitation at 282nm could provide a strong presumptive indication of saliva deposition. |
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