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Visualization of Latent Fingerprint Corrosion of Metallic Surfaces

Authors


  • 1

    A glass fiber pencil is used for accurate abrading of a surface and has a propelling pencil action to expose more or less of the glass fibers—the shorter the fibers showing, the more abrasive the action.

Additional information and reprint requests:
John W. Bond, D.Phil.
Scientific Support Unit
Northamptonshire Police
Wootton Hall
Northampton, NN4 OJQ
United Kingdom
E-mail: john.bond@northants.police.uk

Abstract

Abstract:  Chemical reactions between latent fingerprints and a variety of metal surfaces are investigated by heating the metal up to temperatures of ∼600°C after deposition of the fingerprint. Ionic salts present in the fingerprint residue corrode the metal surface to produce an image of the fingerprint that is both durable and resistant to cleaning of the metal. The degree of fingerprint enhancement appears independent of the elapsed time between deposition and heating but is very dependent on both the composition of the metal and the level of salt secretion by the fingerprint donor. Results are presented that show practical applications for the enhancement to fingerprints deposited in arson crime scenes, contaminated by spray painting, or deposited on brass cartridge cases prior to discharge. The corrosion of the metal surface is further exploited by the demonstration of a novel technique for fingerprint enhancement based on the electrostatic charging of the metal and then the preferential adherence of a metallic powder to the corroded part of the metal surface.

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