Forensic soil comparison for traffic accidents caused by soil clods on roadway

Soil, as a prevalent form of trace evidence at crime scenes, demonstrates considerable forensic value through its transferability and geospatial distinctiveness. Tracing the geographical origin of soil from crime scenes can provide crucial evidence support for court trials and case investigations. This study investigated the forensic utility of soil evidence in traffic accident liability determination using a representative case occurring in the peri-urban areas of Yancheng City, Jiangsu Province, China. In this case, large clods of dry and hard soil were scattered on the roadway, causing an electric tricycle to overturn, which resulted in the driver's death. Given the absence of surveillance footage and eyewitness accounts, we conducted similarity analysis using soil morphological characteristics, pH, particle size parameters, and elemental composition. Multivariate similarity assessment among accident site soils (sample ID: 0-1, 0-2) and reference samples from the suspect vehicle (1-5, 1-6, 3-4, 3-7), parking spot (4-3), and last cultivated farmland before the incident (5-2, 5-3, 5-6) revealed consistent patterns. Notably, sample 1-5 exhibits the highest degree of similarity with the accident site soil. These findings provide useful empirical support for liability determination and fair adjudication in traffic accidents.