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Footwear impressions are the most frequently encountered evidence at crime scenes after DNA and fingerprints. They can provide information to demonstrate or exclude the presence of an item of footwear at a crime scene. Footwear impression evidence became a priority for the UK Association of Chief Police Officers (ACPO) following changes in 2006 in the UK legislation to the Police and Criminal Evidence (PACE) Act 1984. This empowered police officers to take footwear impressions or to seize footwear from apprehended suspects for subsequent examination. This also generated an operational need to evaluate footwear enhancement techniques.

The UK Home Office Centre for Applied Science and Technology (CAST), in collaboration with the Centre for Forensic Science (CFS) at the University of Strathclyde, Glasgow, Scotland, worked together on a strategic research project to evaluate existing chemical enhancement techniques for their applicability to footwear enhancement for marks made in blood, urine, and soil on various fabric surfaces. The James Hutton Institute, Scotland, contributed their expertise and comprehensive experience in soil composition and analysis to that aspect of the project work. The research was led by Professor Niamh Nic Daeid and Dr Katy Savage at CFS and Dr Helen Bandey at CAST. In addition, the research team explored the effects of different soil characteristics on the efficacy of the chosen enhancement reagents with Professor Lorna Dawson of the James Hutton Institute. The laboratory work was carried out by Kevin Farrugia while completing his Ph.D. at the CFS under the supervision of Professor Niamh Nic Daeid.

Figure 1: SEM analysis of fabrics before (left) and after (right) the deposition of blood on: a) white cotton, b) patterned cotton, c) white polyester, d) white nylon/lycra.Figure 1: SEM analysis of fabrics before (left) and after (right) the deposition of blood on: a) white cotton, b) patterned cotton, c) white polyester, d) white nylon/lycra.

The purpose of the research was to scientifically and robustly evaluate and establish the appropriate enhancement techniques and to understand the mechanisms for the development of footwear impressions made in operationally relevant contaminants on different colors and types of fabric. This included establishing the topographical and physical characteristics of the fabrics and influences that these may have on the subsequent enhancement of the footwear impression. Scanning Electron Microscopy (SEM) of the various fabric types and the interaction of the contaminants with these fabrics provided insight as to how materials such as blood and soil penetrated into the materials (Figures 1 and 2). The ‘porosity’ of the fabrics was also assessed. In the case of wet contaminants (blood and urine) the surface morphology of the fabric had little effect on the enhancement abilities of the various reagents investigated, while the success of enhancement on footwear impressions in soil depended on both the soil type and on the fabric surface morphology.

Figure 2: SEM analysis of fabrics before (left) and after (right) the deposition of soil on: a) white cotton, b) patterned cotton, c) black polyester, d) black nylon/lycra.

 

Figure 3: Enhancement of a footwear impression in blood on black cotton (a) and denim (b) with Luminol.

 

Figure 3: Enhancement of a footwear impression in blood on black cotton (a) and denim (b) with Luminol.

Blood
The aim of this work was to provide a comprehensive comparison of the ability of a number of peroxidase reagents and protein stains to enhance footwear impressions made in blood on a range of fabric types and colors. Of the peroxidase stains, Luminol (Figure 3) was the best performing enhancement technique overall, enhancing impressions on all fabrics examined and was the only technique to provide a clear enhancement of the impressions on denim and leather. However, careful application is required as diffusion of the mark can occur. Leuco crystal violet (LCV) and Leuco malachite green (LMG) provide good enhancement on patterned cotton and light colored fabrics but are poor enhancers of impressions on darker fabrics. Acid Yellow 7 is the most suitable protein stain for footwear impressions made in blood and deposited onto dark fabrics (Figure 4). AY 7 provided some excellent enhancement and had the added advantage of fixing the mark in situ so that fine detail could be observed and no distortion of the mark was evident (Figure 5).
 
Figure 4: Enhancement of a footwear impression in blood on black nylon/lycra: a) impression in blood, b) enhancement with AY7 under white light, c) AY7 fluorescence using Blue Crime-Lite™, d) AY7 fluorescence using Quaser 40.

Figure 4: Enhancement of a footwear impression in blood on black nylon/lycra: a) impression in blood, b) enhancement with AY7 under white light, c) AY7 fluorescence using Blue Crime-Lite™, d) AY7 fluorescence using Quaser 40.

 

 

Figure 5: Fine detail within the AY 7 enhanced mark.

Figure 5: Fine detail within the AY 7 enhanced mark.

Alginate casting material can also be used to recover marks left in blood and can easily be prepared and applied at a crime scene if the article cannot be moved to the laboratory. Lifting with alginate followed by enhancement with Acid Black 1 provided good definition for all impressions on all fabrics including denim (Figure 6).

Figure 6: Enhancement of a footwear impression in blood on denim using alginate and Acid Black 1: a) impression in blood before enhancement, b) impression in blood after lifting alginate, c) alginate lift, d) alginate lift enhanced with AB1.

 

Figure 6: Enhancement of a footwear impression in blood on denim using alginate and Acid Black 1: a) impression in blood before enhancement, b) impression in blood after lifting alginate, c) alginate lift, d) alginate lift enhanced with AB1.

 

 

Figure 7: Enhancement of a footwear impression in urine on patterned cotton: a) 2 month old urine impression, b) DFO enhancement under white light, c) DFO enhancement using a Quaser 40 green excitation source.

Figure 7: Enhancement of a footwear impression in urine on patterned cotton: a) 2 month old urine impression, b) DFO enhancement under white light, c) DFO enhancement using a Quaser 40 green excitation source.

Urine
Urine from different individuals can exhibit different fluorescent properties but in general strong fluorescence is observed by using a violet/blue excitation source (350-469nm), viewing with a yellow filter (476nm). Four reagents, 1,2-indanedione (1,2-IND), ninhydrin, 4-dimethlyaminocinnamaldehyde (DMAC), and 1,8-diazafluoren-9-one (DFO) all provide some enhancement of the marks to varying degrees. In some cases enhancement was observed after a period of two months post deposition. DFO provided the best enhancement of footwear marks in urine but only on lighter colored fabrics with more porous fabrics (cotton and patterned cotton) providing the best results (Figures 7 and 8). The presence of dyestuffs or other chemical products were shown to inhibit the observed fluorescence in some cases.
 
Figure 8: Fine detail within the DFO enhancement using a Quaser 40 green excitation source.

Figure 8: Fine detail within the DFO enhancement using a Quaser 40 green excitation source.

Soil
Results indicated that the soils investigated were more likely to respond to reagents that target iron rather than calcium, aluminum, or phosphorus. A range of common soil types found in the UK were investigated. Furthermore, the concentration of iron and soil pH did not appear to have an effect on the performance of the enhancement techniques. Of the chemical enhancement reagents tested, 2,2’-dipyridil was a suitable replacement for the more common enhancement technique using potassium thiocyanate (Figure 9). The main advantages to this alternative are the use of less toxic and less flammable solvents and improved clarity and sharpness of the enhanced impression. However, a slight tendency for diffusion to occur on less porous fabrics (e.g. polyester and nylon/lycra blends) caused some minor distortion of these marks.
 
Figure 9: Enhancement of soil mark on black cotton using 2,2’-dipyridil.Figure 9: Enhancement of soil mark on black cotton using 2,2’-dipyridil.
 

The research completed by the team has been presented widely to academics and practitioners and has led to a series of comprehensive scientific journal publications detailing all of the enhancement methods evaluated in the work. These publications are listed below and can be obtained directly by e-mailing Prof Nic Daeid (n.Nic Daeid@strath.ac.uk).

Publications

  1. K.J. Farrugia, N. NicDaéid, K.A. Savage, H.L. Bandey, (2010) Chemical enhancement of footwear impressions in blood deposited on fabric - Evaluating the use of alginate casting materials followed by chemical enhancement, Science & Justice, 50 (4) 200-204.
  2. K.J. Farrugia, K.A. Savage, H.L. Bandey, N. Nic Daeid (2011) Chemical Enhancement of Footwear Impressions in Blood on Fabric – Part 1: Protein Stains, Science and Justice, In Print, DOI: 10.1016/j.scijus.2010.11.001.
  3. K.J. Farrugia, K.A. Savage, H.L. Bandey, T. Ciuksza, N. Nic Daéid (2011) Chemical Enhancement of Footwear Impressions in Blood on Fabric – Part 2: Peroxidase reagents, Science & Justice, In Print, DOI: 10.1016/j.scijus.2010.11.002.
  4. K.J. Farrugia, H.L. Bandey, L Dawson, N. NicDaéid (2012) Chemical enhancement of soil based footwear impressions on fabric, Forensic Science International, 219, 1-3, 12-28, DOI:10.1016/j.forsciint.2011.11.011
  5. K.J Farrugia, H.L Bandey, S. Bleay, N. Nic Daeid (2012). Chemical enhancement of footwear impressions in urine on fabric, Forensic Science International , 214, 1-3, 67-81 DOI: 10.1016/j.forsciint.2011.07.020

Niamh Nic Daeid is Professor of Forensic Chemistry at the Centre for Forensic Science, University of Strathclyde, Glasgow. She leads a large multidisciplinary research team in forensic science at CFS and has many years of experience in forensic chemistry.

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