I believe all profiles were direct contact. There's no source DNA for contamination to occur. You must have a source. DNA isn't floating in the ether.
You know Italian?
How do other profiles explain how Raffaele's DNA ended up on the clasp, if there is no source DNA of his in the house other than tiny amount mixed with Knox's on a cig in the kitchen?
The simple explanation is Raffaele touched the bra clasp that night which jives with the fact he has no alibi. Every guilty person cries contamination. I think we would have to eliminate using DNA in murder trials if we accept this is contamination.
Wow. So you're sure that the crack forensics team swabbed every single surface in the house for DNA? You're sure that the crack forensics team even swabbed the entire outer (hallway-facing) door of Meredith's room for DNA? You know: the door that Sollecito says he pushed hard against several times on the morning of the 2nd November?*
You're also quite clearly unaware of where the boundaries of low-template DNA analysis lie. You have repeated the entirely misleading nonsense of "abundant amounts" of Sollecito's DNA on the bra clasp, when in fact it's firmly in the low-template range. It's only "abundant" relative to the ludicrously minuscule quantity of the victim's DNA that was allegedly found on the blade of Sollecito's kitchen knife (and which is by every single accepted standard an unreliable and inadmissible result).
The amounts of DNA that are apparently present on the bra clasp call for sophisticated low-template testing protocols (oops, they weren't followed....), and for scrupulous care to be taken in collecting and storing the item being tested (oops, the bra clasp was kicked around on the floor for six weeks, passed round like a birthday present when it was finally collected, and it's since been destroyed as evidence by crack forensic specialist Ms Stefanoni....). The apparent presence of other male profiles on the clasp DOESN'T mean or imply that other as-yet-unidentified men were also complicit in the attack and murder. Rather, it implies that grossly insufficient care was taken (whether in the lab or at the crime scene) to prevent widescale contamination of the bra clasp.
Lastly, time once more to nail the myth that "
we would have to eliminate using DNA in murder trials if we accept this is contamination." This is a lazy and/or ignorant "argument" that does no more than indicate a fundamental failure to understand the very real issues surrounding low-template DNA evidence. You manifestly fail to (or refuse to) understand that when dealing with such tiny quantities of DNA, the results are meaningless and invalid UNLESS extremely strict protocols and processes are scrupulously adhered to from identification of exhibits all the way through to testing and interpretation of results. This type of DNA analysis is an entirely different ball game from "standard" DNA work where any contamination is totally swamped by the (true) abundance of source DNA. Unfortunately, neither the crack forensics team nor the crack world-renowned testing technician (who, oddly and improperly, also headed up the forensics crime-scene team!) seemingly had the first idea of what they were doing when it came to the extreme care, skill and safeguarding that are absultely mandatory when dealing with low-template-level samples.
* Hint: the police didn't do any such swabbing. All that the known DNA results tell us is that
of those items which the crack forensics team did swab, Sollecito's DNA was only present on that cigarette butt. But that is entirely different - both logically and in practice - from making the incorrect and misleading assertion that the only place within the cottage where Sollecito's DNA was present was upon that cigarette butt. (Unless one is either ignorant or confirmation-biased of course, in which case it's just fine to bandy around that kind of stuff
)
