DNA profiling (3)

We've seen that it is dangerous to automatically assume that a match between a DNA sample and a person's profile proves the sample to be that person's. But even if we accept that it is, there are other factors to be considered. DNA profiling is often referred to as "genetic fingerprinting" but there's one important distinction between fingerprinting and profiling. If my fingerprint is found at a certain place, or on a certain object then, in the absence of any jiggery-pokery, that is evidence that I was at that place, or touched that object. But DNA is transferable - it can end up in places where you've never been, or on objects that you've never touched. If I go into a shop and pick up a piece of pottery, say, and then put it back and leave the shop, and then someone else comes into that shop and picks up the same piece of pottery, there's a chance that my DNA will be transferred to their hands, and if they then go into another shop, where I've never been, and touch something there, my DNA may end up in that other shop. So apart from the question of false matches, we also have the problem of transference. And then there's the "prosecutor's fallacy" - but we'll leave that for next time.