This forensic case discusses how detailed morphological (texture, structure, colour, roots, particle shapes), chemical (pH, EC, elemental composition) and mineralogical (X-ray diffraction) investigations on soil-regolith material from a shovel, boots and jewellery combined with field observations and geological/soil map examinations were used to discriminate and match soils to help locate two buried bodies.

The suspect was arrested on Yorke Peninsula, 150 kilometres from the murder scene in the Adelaide Hills a day after two women disappeared. Although the victims’ bodies had not been located, there was an overwhelming case against the suspect because a bloodstained shovel with soil-like material on the blade was recovered from his vehicle.

Presence of angular quartz and 3mm white flakes together with low pH and EC values ruled out the origin of the soil from Yorke Peninsula but rather from the Adelaide Hills. Identification of crystalline kaolinite, mica and talc combined with geological/soil map information suggested its origin from a gravel quarry occurring in a specific province of strongly weathered regolith. This information, together with other physical evidence, led police and pedologists to undertake investigations in a quarry. Samples were taken of waterlogged soil-regolith in the quarry because their morphological features closely matched soil-like material on the shovel. XRD patterns of the waterlogged soil-regolith were identical to soil-like material on the shovel, suggesting the victims were buried at this site. This led detectives to conduct repeated observations at the waterlogged-site. Decomposition of bodies led to fox activity, which revealed their locations in the quarry 3 weeks after the victims’ disappearance.