So... why exactly are the police trying to match soil samples from his van (Im presuming it's the VW T3 Westphalia) to the soil samples taken from Arade Reservoir? What would this actually prove if they were able to match the samples?
Well, if they were able to successfully match only the soil samples then it would only prove he (or someone else) had been to Arade Reservoir in his van before. It would prove absolutely nothing with regard to CB murdering MM. Therefore, it must be what else was or will be found within the soil samples taken from Arade Reservoir and in his van which can be linked to MM; which could only be bone (probably fragments) and/or clothing (probably microscopic).
A few points I would like to add...
1. If it was only soil samples found in his van, and these samples do in fact match the soil samples taken from Arade Reservoir - yet bone and/or clothing from MM is also found within the Arade Reservoir samples - how does this prove CB murdered MM? Surely it only proves that MM was at Arade Reservoir at some point either alive or deceased (if only clothing is found), or deceased if bone fragments are found.
2. They must, therefore, have found either bone and/or clothing within the soil samples taken from CBs van. In regard to bone fragments, however, if they had found bone fragments from MM in his van, then this would already be stronger evidence to convict CB than finding bone fragments from MM at Arade Reservoir. So I dont see this being the case. 3. By process of elimination then, it must have been MMs clothing they found within the soil samples taken from CBs van, and they are hoping to match the soil samples taken from his van (with her clothing in them) to the soil samples taken from Arade Reservoir (with her bone fragments and possibly clothing in them).