Thesis

An evaluation of enhancement techniques for footwear impressions made on fabric

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Awarding institution
  • University of Strathclyde
Date of award
  • 2011
Thesis identifier
  • T12872
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Abstract
  • Robust comparisons of enhancement techniques may be limited due to variations, (e.g. pressure, contaminant and surface) in the preparation of test footwear impressions. The use of chemical enhancement techniques on porous substrates, such as fabrics, poses several challenges predominantly due to the occurrence of background staining and diffusion as well as visualisation difficulties. This is the first systematic study to examine both a wide range of enhancement techniques and the effect of the interaction between the fabric and the contaminant on the subsequent enhancement. The work focuses on three commonly encountered contaminants in casework namely blood, urine and mud. A mechanical stamping rig was developed and used to control the delivery pressure of the mark. The surface topography and porosity of the fabrics studied were investigated and had an effect on the enhancement abilities of the various techniques. This appeared to be due more to the porosity of the material rather than the topographical nature of the fibre surface. This was particularly the case for the wet contaminants (blood and urine). A mechanism for grading the enhancement ability of the reagents for a given impression was investigated and refined for impressions in blood using practitioner and forensic science student volunteers. This provided a potential means of subjectively determining both the quality and quantity of enhancement provided by a given reagent or enhancement mechanism. The results demonstrated that several chemical techniques were suitable for the enhancement of footwear impressions in blood, urine and mud on light coloured fabrics irrespective of the nature of the fabric. Fluorescent and chemiluminescent techniques provided excellent contrast on dark surfaces when enhancing footwear impressions in blood, but were less successful for the enhancement of impressions in urine and mud. Oblique lighting did, however, provide limited enhancement of mud contaminated impressions on dark fabrics. For impressions in blood and urine, the surface topography of the fabric had little effect on the enhancement abilities of the various reagents investigated, while the success of enhancement on footwear impressions in mud depended on both the soil type and fabric surface topography.
Resource Type
DOI
Date Created
  • 2011
Former identifier
  • 832993

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