Sleuthing in the digital age – crime scene technology increases conviction rates
In his 1897 detective novel 'The Scarlet Study', author Sir Arthur Conan Doyle had Sherlock Holmes observe "There is no branch of detective science that is so important and so much neglected as the art of tracing footsteps". Over a century later, forensic science is finally able redress this neglected area thanks to a novel project based in the Department of Electronic and Electrical Engineering's Image Engineering Lab at the University of Sheffield, which has culminated in a sophisticated new system for recording and identifying footwear, glove and tyre marks at the scene of a crime.
Changes in Police powers, which came into force in January 2006, now permit footwear evidence to be treated in the same manner as fingerprint and DNA evidence. As a result, the Police now have the right to acquire impressions of all arrestees' footwear, which can be held and searched on a national database.
The recovery of footwear marks from crime scenes has been patchy across the individual UK Police forces, but it is recognized that there is more chance of recovering footwear marks from burgled premises than fingerprint marks, which can provide very valuable intelligence and sometimes evidence for use in court.
Led by Professor Nigel Allinson, Research Fellow Dr Maria Pavlou has developed a robust unit for use in custody suites for the recording and classification of a suspect's footwear. Current methods for identifying shoe models from impressions or marks are labour-intensive and prone to error. To combat this, the team's fully automatic Latent Image Markup and Analysis (LIMA) system allows for the rapid and accurate classification of shoe models. Marks left by an intruder's shoes in dust, on surfaces such as wood, concrete or tile, are lifted using gels or electrostatic techniques like those used in a traditional photocopier. The team's LIMA software is 10 times faster than existing techniques, taking less than 20 minutes to identify a print compared with 24 hours using the traditional approach.
Professor Allinson explains: "Luckily, most criminals wear trainers and the complexity of the outsole patterns results in many 1000s of identifiable features. By cross-comparing these features with 1000s of shoe soul images on our database, we can obtain a short-list of likely candidate models; more intensive graphical models are then employed to identify the specific model. We have also been able to refine techniques for very large reference sets, cope with partial and scuffed marks, and provide tools to link a suspect's shoes to the matching scene marks".
Further work by Dr Pavlou has led to the development of a generic imaging workstation for use in forensic laboratories that can be employed to mark-up footwear, gloves, tyres, etc. to create reference databases, identify crime scene marks, compare marks, produce reports – in essence, a complete solution for all forensic imaging needs.
Key to the operation of the system is the way in which Scene of Crime (SOC) officers record fingerprint and other marks at crime scenes, using a laptop, scanner and G3 wireless card. The technology allows images to be compressed and securely transmitted, which has reduced the time taken to identify latent prints, in turn helping to increase burglary conviction rates.
Having worked with the police and other organizations to further the application of the technology into operational practice, the team's LIMA software has now been rolled out to all UK police forces. Dr Jeevandra Sivarajah, supported by the National Policing Improvement Agency, was integral in bringing this work to fruition.
The team are now working on methods of recovering fingerprints from curved surfaces, as well as reconstructing crime scenes, using sophisticated computer software, from two-dimensional pictures.
For further information, please contact Professor Nigel Allinson:
email : n.allinson@sheffield.ac.uk
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Notes: This research was funded by the Engineering and Physical Sciences Research Council (EPSRC), one of the UK Government's 7 Research Councils, and the Yorkshire Concept Fund.