Oops, didn't see your post before highjacking....I thought I had heard of that....I digress.
I don't think you can really correlate materials belonging to other unknown persons as being proof of an intruder. That's a lot of ground to cover.
Part of Darlie's defense was that she was some kind of supermom who had neighbor kids climbing all around the house all the time. These kids can transfer items from their own homes into the Routier home. I know that Darlie cleaned that day, and that the house was kept by a maid, but let me put it to you like this: If I called a hazmat team into my home and asked them to disenfect it from top to bottom, without ripping out the carpets, drapes, removing furniture ect, I can guarantee you that I could walk back into my homes, minutes after their departure and find numerous hairs. As someone who has people visit on a regular basis, I could type all my friends and family, and still find hairs that they brought in from "thier" homes via transfer from thier clothes, bodies, etc.....so in essense, something as simple and as common as hair isn't going to mean anything.