police investigations are never about finding zero evidence and therefore drawing a conclusion that the lack of evidence 'proves' a negative, eg "he didn't wander", or "no one in the family harmed him".
Investigations are about finding evidence that proves whatever did specifically happen.
If no evidence is found, then we just do not know what happened. No conclusions can be drawn.
My reading is the opposite. They did find evidence... They found evidence that the traces that would be expected if Gus wondered off were not there....
To illustrate, if a parent leaves an unopened ready-made meal for a child to open and eat, and then finds that the child has not openned the meal and the meal is still inside, then the parent has evidence that the child did not eat the meal.
OR
If you claim to have just walked across sand or snow or whatever and did not leave a trace, then I would doubt your story if there was no trace within a time in which it would be expected that traces would remain.
The police found evidence that Gus did not wander off.... not because they saw or found nothing, but because they found a farm house surrounded terrain that lacked the signs of disturbance experts would expect.
I completely understand that they may be misreading the evidence. They may have missed signs or disturbed evidence of Gus's footprints, etc.
If I was on a jury and they presented their findings that the area lacked traces of a child wandering off, then I would have to weigh their proof of that, the reliability of their expertise, of experts in what traces would be expected, and so on.
It is not that they found nothing, but that they found a farm that lacked the traces that would be expected if a child wandered off.
How does that work with the case of missing woman Lynette Dawson née Simms? Somehow the Crown proved beyond reasonable doubt that she was murdered.
Exactly...
Chris Dawson's behaviour afterwards was not consistent with a grieving husband, but of a man who was trying to create the impression that his wife had abandoned him and the children, and who wanted to be able to have a young girl, with whom he had an overly familiar relationship, move in with him as soon as possible afterwards, without the hinderance of the presence of his wife.