"It matters not a whit whence the DNA emanated" hehehehehehehe. If only Iwaswere so erudite, eh?!
And as you (and Massei) are obviously wholly correct to point out, it DOES "matter a whit" "whence" the DNA "emanated". We are talking here about a bathroom sink - a sink where Knox frequently washed her hands and face (thus potentially depositing epithelial cells), spat out toothpaste (thus potentially depositing cheek lining or gum cells via the saliva/toothpaste mix spat out - a mix which is notoriously claggy and persistent in a sink bowl, it ought to be noted), or potentially deposited blood via entirely innocent means (a cut on the gums, or a bleeding ear piercing).
There is no evidence that the sink in the small bathroom was cleaned on a regular basis - it's a fairly high probability that the prosecution would have sought hard to find out when it was last cleaned, so the very fact that this was not raised in court suggests in and of itself that the sink possibly hadn't been cleaned in, say, over a week before the murder. So there is obviously the very real and feasible possibility of Knox's DNA from days previously being co-present with Kercher's blood DNA from the night of the murder (and, for that matter, Kercher's non-blood DNA from the days previous to the murder - from Kercher's own toothbrushing, handwashing etc).
When you add into this mix the egregiously improper and incompetent manner in which the swabs of the sink were taken, the sink evidence is effectively ruled null and void in terms of its probative value against Knox. End of story.
Oh and Garofano - in his boneheaded assertion that blood is the body fluid with the highest concentration of DNA - not only fails to include semen (which has a hugely higher concentration of DNA than blood) but also saliva, which typically also has a higher concentration of DNA than blood owing to the number of cheek-lining and gum cells it contains (though the DNA in saliva can often be of lower quality owing to bacteria and other enzymes present in saliva). So Garofano is wrong on two counts. How did this guy ever get to his position? It certainly can't have been on account of his scientific brillianceJust one more example of the incompetence, patronage and corruption which plagues the broken state of Italy..........
The way the swabs were collected from the crime scene video should have been enough to have the results thrown out as evidence.
They swabbed over such a large area I'm surprised the next door neighbours DNA wasn't mixed in as well.