In reading this thread, I keep seeing this desire for "proof of contamination". What exactly would be sufficient for "proof of contamination" and is this really the appropriate standard?
To bookend this issue, on one end you have "contamination is always possible therefore any DNA evidence is unreliable". The other end is "any DNA result needs to be accepted unless the defence can prove contamination". Both seem to be unreasonable positions.
Given it is the prosecution's case to prove, I would think the standard should be the prosecution needs to demonstrate that the evidence was handled and procedures executed with sufficient care such that the risk of contamination was at an insignificant level. The defence does not need to "prove contamination" but rather show that the evidence handling or processes were performed in such a manner as to raise the risk of contamination above an acceptable level.
I would appreciate feedback as always.
It's really not that simple, however. Sure, the bra clasp handling was less than proper. HOWEVER, that in and of itself does not provide a means for contamination of a level we see on the clasp. That is paramount to the contamination discussion.
What the one side would have us believe is that if handling is improper, contamination has happened without providing a plausible contamination scenario.
If we accept that contamination did happen to the clasp DNA, then why is Sollecito's DNA in a higher concentration than that of anyone who had much more access to the room than Raffaele? Why is it Raffaele's DNA and not any of the investigators/forensics teams/roommates of Meredith who either had reason to be in Meredith's room or directly had contact (albeit, wearing gloves, etc) with the clasp.
And we have the same issue with the knife. Ok, so we accept that it could be contamination. How did the contamination occur? And if it was from contamination, why did Raffaele feel the need to write a completely bogus story (read: lie) about how the DNA arrived on the knife - it leads one to believe he
expected Meredith's DNA to be there (speculation).
It's not that we're arguing the extremes, at least, I'm not. I'm arguing that we don't have a logical, plausible scenario to believe this is contamination.
The Prosecution has presented that the DNA is not contaminated, Dr Stefanoni was questioned for 2 days regarding her labwork. If the Defense chooses to claim contamination occurred, then they need to provide a plausible contamination scenario. Simply screaming "See, contamination can happen and the bra clasp had "dirt" on it" is insufficient to explain the DNA found on the clasp.