Q: Professor, the analysis of the Scientific Police has been questioned by the court-appointed experts Vecchiotti and Conti on three basic points: contamination, the attribution of DNA to Sollecito, and the issue of the smallness of the amount of material found -- it's Low Copy Number, that is, the small amount of material found on the items.
A: That's right, and basically these are three points that should always be taken into consideration in forensic analysis. However, whenever you talk about contamination as a hypothesis, you always have to prove it: establish the origin, and show that contamination has indeed occurred. Because even though it is a possible phenomenon, it is also a rare phenomenon in DNA analysis.
Q: In this case, how are you able to rule out contamination of the items?
A: If there's been contamination -- DNA ending up somewhere it shouldn't be -- I'm going to find it in the analysis. The second important thing is that when something contaminates, it's impossible for it to contaminate just that item and only that item. And here we have contamination by what? The DNA of the victim -- which was analyzed 15 days before or 7 days before the item, according to the two situations -- so what happened? After 7 days, this contamination disappears? But I should have found it in other items examined by the police. I went to the police to check these tests; and in something like a hundred analyses that they did, I never found any trace of this contamination.
Q: About the bra clasp: is Raffaele Sollecito's DNA on the bra clasp, or not?
A: Look, Sollecito's DNA is there, it's there in a complete manner...
Q: How do you know?
A: From the presence, for example, we can see this table of what was reported: this is the DNA of Sollecito; each number here corresponds to a genetic characteristic: 12, 13, 14. This is the DNA found on the item. 13? 13 is there. 12? There's 12. 22, there's 22. There are also other characteristics; these can be for example, DNA belonging to another subject. But that doesn't change the fact that he is there.
Q: The appeal trial introduced this term, Low Copy Number. What does this refer to?
A: Not always, in a murder investigation, do we find ourselves in a perfect, standard situation. Sometimes we have to make do with what we have. But quantity is not always linked to quality. That is sometimes even small quantities are clean, clear, and unequivocal, and can be used.
Q: Professor, is the DNA of Meredith Kercher on the knife blade unequivocal?
A: I don't think there's any doubt about this -- I think even the experts on the other side agree on this. The crucial point is that what they claim is that the quantity is not enough to be taken into consideration.
Q: Professor, what are the limitations of this review?
A: In my opinion, the fact that for example, Vecchiotti and Conti also found a small trace of DNA, which here too was also called "Low Copy Number", which wasn't analyzed. In my opinion, it should have been analyzed. Also because, if there is another DNA trace, let's see what it is.