I'd like to see a reasoned, thought out response to this post from Chris (Halides), Bruce, Dan O, etc. These are, without a doubt, the reason why the clasp is considered to be a valid piece of evidence.
Regardless of whether the cottage was sealed, regardless of when the clasp was collected - there was no means for Raffaele's DNA to contaminate the clasp. To claim this is the case is to defy the laws of physics - and yes, I know what I'm claiming.
To believe Raffaele's DNA is due to contamination, we must believe that his DNA was somehow in Meredith's room. Since we're arguing he wasn't involved and he was, thus, never in Meredith's room, the argument necessarily requires that someone else brought the DNA in with them.
As there was only one other place in the cottage that tested positive for Raffaele's DNA, a cigarette butt in the kitchen that had been collected prior to the clasp, how did Raffaele's DNA arrive in Meredith's room?
He never entered the room during the "initial" discovery by the Postal Police.
We've established that dust is not sufficient to provide such a large concentration of a single individual's DNA - additionally, we'd expect the level of Raffaele's DNA to be on par with that of everyone else that had ever entered the room, including Inspectors, Meredith's BF's, Meredith's roommates, etc. And yet, Raffaele's DNA was found in a concentration of magnitudes greater than that of Amanda (and presumably the other 2 roommates - regardless of whether the two unknowns are the roommates are not, we can be sure that Raffaele's DNA was in a concentration higher than any of Meredith's 3 roommates).
So, if anyone would like to continue believing the contamination bit, I'd like to see a valid, rational response as to where, exactly, the DNA came from if not Raffaele himself.