When all is Tread and Done - Is there evidential value?

Since 2018, the YatH RSSS footwear unit has experienced growing demand for upper comparison casework, with a 25% increase in evidential comparisons between 2022 and 2023. Phase 1 developed a cost-effective, repeatable method for capturing 360° images of footwear under white and near-infrared light. Phase 2 investigated the potential evidential value of footwear uppers caught on camera (e.g. CCTV) as a form of identification. It focused on factors that influence the interpretation of class and individual characteristics (e.g. brand and damage, respectively) that could influence the evidential outcome of a comparison. The project supports multiple areas of the Science and Technology strategy. There is no literature on how environmental factors can influence our ability to see features on footwear uppers. There is also no literature on common features of wear, where they predominate on a shoe upper and how long they persist which highlights the need and novelty of this research.
The work generated evidence-based insights into footwear uppers in real-world conditions, focusing on the visibility, commonality, persistence and material-dye interactions of footwear characteristics, particularly under near-infrared (NIR) imaging. Key outputs include a novel image quality assessment tool, a dynamic footwear characteristics database, and analytical findings with direct forensic relevance. The image quality tool, informed by controlled experiments, will be showcased at a stakeholder event to gather feedback for refinement. A training module on its use will be delivered in Phase 3. The interactive dashboard, developed through the commonality study, enables continuous data entry and real-time trend analysis, enhancing its value as a long-term forensic resource.
Each work package contributed distinct findings.
1. Lighting, shoe colour, distance, and material influence characteristic detection. Notably, light-coloured shoes performed better under white light, while dark shoes showed improved contrast under NIR. Glare and material reflectivity were also found to impact visibility.
2. Characteristics were tracked over nine-month period, revealing that features such as creases, dents, and stains often persist, while others—particularly dirt—tend to degrade. Some characteristics evolved over time, supporting the forensic value of longitudinal shoe data.
3. 10,000 images were captured from 1,000 shoes, with over 7,600 annotated characteristics. Common features included stains, creases, and dents, predominantly located on the toe and sole. Less frequent but more distinctive features such as holes and fraying may hold greater evidential value.
4. Analysis of 30 shoes showed that material type alone did not fully explain NIR visibility. FTIR and HPLC results suggest that dye types and binding agents influence how materials appear under NIR.