Thanks, Joshua. It just struck me as a sweeping, and potentially unhelpful, statement to make. In other words, there surely must be coincidences when we're dealing with serial killers.
I think serial killers are just as likely to attract coincidences as anybody else, no more, no less. Meaning that you are correct - we must allow for coincidences in that context too, just as we do otherwise.
A problem only arises if we start getting far too generous in allowing for - or even conjuring up ourselves - coincidences in heaps to explain away what otherwise seems to clearly point in a certain direction.
As an aside, the barrister James Scobie, of Lechmere docu fame, says in the documentary that when coincidences start to mount up in the Lechmere case, it becomes one coincidence too many. And since I have seen material that was not in the docu, I can say that Scobie spoke very critically about how people are too easily taken in by how possibilities open up escape routes.
I think he is very correct in that respect - many of us are way too happy about ourselves on account of our ability to cook up alternative suggestions in order to try and nullify what looks like damning material. It is a good thing to be cautious not to convict on too little, but when this ambition turns to an exercise in accepting coincidences, knee-jerk fashion, then we are doing research, history and logic a disservice.
Believe me, I know about this, since I have personally seen it happen.
Presumably, this is what David Wilson is after too: Let´s not get naive when dealing with serial killers.