Examining the transfer of soils to clothing materials: Implications for forensic investigations

Soil forensics has proven instrumental in assisting criminal investigation, and there is an increasing demand for experimental studies on such trace evidence. Here we present the first detailed study on the influence of clothing materials on soil transfer. We adopt an experimental approach to test the transfer of five common UK soils to five different clothing materials. Our experiment is designed to represent victim or perpetrator contact with soil at the scene of a crime. We highlight the complex relationship between soil transfer and clothing material type. Whilst over half of our soils tested displayed differential transfer to different clothing materials, soil moisture content and soil type were found to have a greater influence on the transfer of soils overall. Soil transfer is typically more effective across all material types when soils are wet and saturated. However, we find the relationship between soil transfer and material type to be more complex when soils are dry, with a significant bias in soil transfer to fleece material, which we attribute to static attraction. Encouragingly, for the analysis of forensic soils recovered from clothing artefacts, each of the transfer experiments we conducted led to soil transfer to every tested material. We suggest that future empirical studies now focus on the persistence of soils over time to clothing materials after transfer has occurred, and the transfer and persistence of soil palynomorphs present within soils.