Left: bi-plot after Principal components and classification analysis based on correlation of the content of the 54 chemical elements (empty marker, not all labelled) in the 29 soil samples (full marker).

<p>The variance explained by the each principal component is shown in parentheses. Right: plot of canonical scores after Discriminant analysis with canonical analysis performed with the four chemical elements most, and significantly, correlated (absolute value) with factor 1 (Cs, Ga, Ca, S) and factor 2 (Cd, Zn, Hg, Sr). Classification of soil samples has an high probability to be correct (93%) as the predicted classification deviates only for sample “Le”, that is not distinct from “X” (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0020222#pone-0020222-g001" target="_blank">fig. 1d</a>). Since these two samples are in the same group (the green one), group classification is 100% correct. For technical details of multivariate techniques see Statistica 7.0 Electronic Manual (Statsoft Inc., 2005).</p

Results of the analyses on the soil samples compared with two specimens of soil (CarR, CarL), found respectively on the right and left carpets of the suspect's car floor.

<p>a, b) ICP analysis of the content of 54 mineral elements. a): Box and whiskers synthetic representation of the variability of the 12 zones; b) Cluster analysis (single linkage, Euclidean distance) of the data; c) Amplified Ribosomal DNA Restriction Analysis (ARDRA) of the soil bacterial communities. The Neighbour Joining dendrogram resulting from Pearson correlation analysis of the combined three enzymes electrophoretic profiles is shown. The horizontal scale indicates the percent distance. In b) and c) sample replicates are included to show the degree of inter-replicate variability.</p

Air view maps of the crime scene and surroundings depicting the sites from which samples were taken, starting from the murder spot, and at increasing distances.

<p>The inset map of Italy shows the area location as well as the sites of two soils taken at far distance as outgroup references. X: spot where the corpse was found (margin of a corn field), CF (inside corn field), Le (ridge of the levee bordering the corn field). 1.7 Km, 3 Km, 18 Km, 19 Km: sites located at 1.7, 3, 18, 19 kilometers from the murder site and sharing the same crop (corn); 1.8 KmF: (fallow), site located at 1.8 km but not cropped for over 50 years and featuring natural vegetation and secondary growth. Sar: soil from an uncultivated area in Sardinia (Castelsardo); Alp: soil from an uncultivated area in the Alps (Soranzen). All samples, except the two outgroup references, were chosen in equivalent soil conditions as regards parent material, depositional basin river and soil type (Hypercalcaric-Fluvic Cambisols, WRB 1998, or Oxyaquic Eutrudept fine-silty, carbonatic, mesic, USDA 1998) to minimize the variability that would occur across different soil types. For details and exact coordinates, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0020222#pone-0020222-t001" target="_blank">Tab.1</a>. Scale bars equal: 500 km (a); 5 km (b); 500 m (c); 50 m (d).</p

Location of sampling sites: latitude and longitude coordinates in decimal values.

<p>The “Car” samples were found within the car impounded from the suspect.</p

Scheme of the ditch after the flood, and modelling of 1-m length.

<p>Scheme of the ditch after the flood, and modelling of 1-m length.</p

The experimental site.

<p>Left: the drainage network, with indication of inlet (A) and outlet (B) of the ditch and the direction of the flow; this image is similar but not identical to the original, and is therefore for illustrative purposes only. The Centre: overview of the ditch next to inlet. Right: detail of the flooded bed after the simulated runoff event (Photos: S. Otto and S.E. Pappalardo).</p

Concentration of herbicides in water in the first and second flood; all values in the third flood were below the detection limits.

<p>Mesotrione: empty circles; metolachlor: empty squares; terbuthylazine: full triangles. The lower axis is the distance from the inlet (m). The drinking water limit (0.1 μg L^-1) is indicated. Detection limits: mesotrione = 0.070 μg L^-1, S-metolachlor = 0.020 μg L^-1, terbuthylazine = 0.014 μg L^-1.</p