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Title: The Electrochromic Enhancement of Latent Fingerprints on Metal Surfaces
Authors: Beresford, Ann Louise
Supervisors: Hillman, A. Rob
Award date: 31-Jul-2013
Presented at: University of Leicester
Abstract: Fingerprints are unique to individuals and have been used as a method of identification in criminal investigations since the late nineteenth century. The majority of fingerprints are latent, i.e. non-visible, and require enhancement for their visualisation. Although many methods have been developed for this purpose, the recovery rate in the form of a useable print, is still disappointingly low for metallic surfaces, especially from discharged cartridges. This work aimed to explore the application of a new technique to utilise the insulating properties of fingerprint deposits, on a range of metallic surfaces. Fingerprint residue can ‘mask’ the surface preventing the electrochemical deposition of a reagent on the bare surface. Here, this takes the form of two different electrochromic polymers, polyaniline and poly-3,4-ethylenedioxythiophene, to produce a negative image of the print. Fingerprint samples were subjected to diverse environments for a range of time intervals. The enhancements were graded on a five point scale devised by Bandey, where prints graded 0-2 are considered unusable and prints graded 3-4 are usable for identification purposes. Using this scale the technique was assessed in a comparative study with existing methods (powder dusting, wet powder and superglue fuming). The outcomes identified superglue fuming as least effective and poly-3,4-ethylenedioxythiophene to be the material of choice when an sample’s history was unknown. Exploitation of the polymer’s electrochromic properties (oxidation/reduction via applied electric potential), to optimise contrast between print and substrate, resulted in the upgrading (from unusable to useable) of 16 % of samples. Project objectives were achieved; the technique was applied to challenging surfaces via the progression from model substrates to alloys to evidentially viable items. Latent fingerprints were enhanced on stainless steel, nickel plated brass, copper, lead and most importantly previously fired brass cartridges.
Type: Thesis
Level: Doctoral
Qualification: PhD
Rights: Copyright © the author. All rights reserved.
Description: Due to copyright restrictions the published articles have been removed from the appendix of the electronic version of this thesis. The unabridged version can be consulted, on request, at the University of Leicester’s David Wilson Library.
Appears in Collections:Theses, Dept. of Chemistry
Leicester Theses

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