He is no doubt trying to limit the chances of being caught in his lie. The less he says, the better for him.
If this attack happened, Prof. Mirecki will lead the police to the exact spot, where they can examine physical evidence that may lead to the solution of the crime.
If this attack never happened, Prof. Mirecki will never lead them to an exact spot, because the police might be able to examine physical evidence and determine that no attack took place.
So, for my purposes, whether or not he leads the police to a specific location will be the best objective indicator of whether or not this attack took place. Until he does, this does not pass the sniff test.