Let's say I got arrested for a crime and the only evidence they had was that the criminal was British and a DNA sample. In court, the prosecution says "The chances of the DNA sample providing a false positive are a million to one, therefore you are almost certainly guilty"
I reply, "No, the event - 'DNA sample coming back positive' - has already occurred. There are now two possibilities, one is that I am the criminal, the other is that it is a false positive. There are 60 million people in Britain so 59 people would have given a false positive result. Therefore the chances of me being the criminal are 60-to-1 against. I am more likely to be not guilty"
I remember reading somewhere (EvC ?) that this approach is actually being used in U.S. Courts. It even has a special term for it. I have no idea of the success/failure rates.
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