title: Optical enhancement of fingerprint deposits on brass using digital color mapping.
abstract: The reflection of visible light from α-phase brass subject to surface oxidation in air at elevated temperatures is investigated. X-ray photoelectron and auger electron spectroscopy confirm that covered areas of brass (not exposed to air) display dezincification but an absence of significant surface oxidation, confirming a differential oxidation mechanism. Visualization of differential oxidation is shown to be enhanced by selective digital mapping of colors reflected from the surface of the brass using Adobe(®) Photoshop(®). Enhancement is optimal when the brass is heated to ∼ 250°C with areas of oxidation having a mirror-like appearance. The use of this enhancement method to produce a faithful image of fingerprint ridge characteristics is demonstrated on brass shell casings where fingerprints were deposited prefiring.
authors.affiliation: Northamptonshire Police, Force HQ, Wootton Hall, Northampton, NN4 OJQ, UK. john.bond@northants.police.uk
authors.forename: John W
authors.initials: JW
authors.lastname: Bond
mesh_terms: D003116:Color; D003300:Copper; D003343:Corrosion; D003878:Dermatoglyphics; D005389:Firearms; D044709:Forensic Ballistics / Q000379:methods*; D006358:Hot Temperature; D006801:Humans; D056951:Photoelectron Spectroscopy; D012984:Software; D015032:Zinc
chemical_list: C048399:brass; D003300:Copper; D015032:Zinc