Integrated, multiscale forensic soil science applied to an unsolved murder case in Italy

Soil forensics is not only a well-established research domain but has also been used in numerous successful international searches for burials and as trace evidence to help police and law enforcement in solving criminal, environmental and terrorism investigations. However, despite the confidentiality and legal constraints in case work in many parts of the world, some actual case studies using soil materials as evidence in court hearings have been published in international journals and books. This paper presents a case from the Campania region in Italy where soil analysis played a pivotal role. Employing a multiscale integrated approach encompassing soil microtomography, morphology, chemical analysis and geography, the study aimed to discern the origin of questioned soil residues found on a victim of crime. Results highlight the significance of considering spatial variability and an appropriate choice of analytical methods. The sequential and multiscale approach facilitated timely investigation without incurring unnecessary costs. Soil morphological and chemical analysis revealed inconsistencies between soil on the victim and soil at the suspected crime scenes, narrowing the investigative area down to approximately one square km. While detailed sampling did not yield statistically significant results, the evidence provided crucial insights, aiding investigators in working out what happened and helped in building a narrative around their case. The analysis indicated contact with a primary scene where the victim was likely dragged (over a Calcisol) and a final deposition site (over an Andosol) where the body was found. While potential murder sites were excluded, final guilt attribution remained inconclusive, and as in all trace evidence evaluation, it is not the role of the forensic soil scientist to consider the level of guilt, but to provide factual soil forensic evidence to assist the justice system. This study exemplifies the use of soil forensics in informing criminal investigations and highlights the complexities that can be involved in establishing comparability between soil samples.