Apologies.
It is really hard to explain things, especially if you come from a metric background, especially without seeming condescending. I not others have explained cc, mm, microns. (Thanks Numbers)
FWIW (for what it is worth), I do not think comparison with grain of salt is useful. (As Davefoc says). But grinder asked me to validate his estimate, I tried to do it by a different method.
As has been said, the real point is that there was mixed DNA present on the bra clasp. The dominant contributor by far was Kercher.My estimate looking at the epg (electropherogram) is that the non Kercher DNA was about 10%.1 Steffanoni's was about 17%. The minor contributors were more than two. The quantity of DNA for the minor contributors falls into the LCN range where a number of methodological problems limit the reliability of testing. Equally the DNA is 'trace' DNA not attributable to any tissue. It is well documented trace DNA may result from secondary + transfer, and cannot be assumed to result from direct touch by the contributor.
Balding a statistician from UCL has looked at how you attribute mixed DNA profiles, his methodology is sound. Like all estimates the more information one has, the more reliable the estimate. It would have been better if profiles of Kercher's boyfriend(s) and other flatmates were available for comparison. It does seem probable that Sollecito's profile was in the extract profile attributed to the bra clasp.
The suspect centric approach is exemplified here. Sollito's DNA is assumed to result from participation in the murder of Kercher, whilst other contributors are assumed to be a result of innocent transfer. The presence of Sollicito's DNA is then used as evidence of his participation in the murder. This is a circular argument his DNA is evidence of his guilt because he is guilty. The DNA of others is not evidence of guilt because they are not guilty.
1http://themurderofmeredithkercher.com/images/b/b5/BraDNA2.png
Locus:
CSF1PO KERCHER 12, 12 Bra Clasps 12/10 SOLLECITO 10, 12
The data is the same no matter which site is is posted on. Look at the original data do not take anyone's word for it.
Hey P, thanks very much for replying. And I appreciate all the effort in trying to explain these issues to the uninitiated.
One other point which Marasca raised, was that since Sollecito's DNA run resulted in only a single run, when the experts had testified that at least two were required, from the court's standpoint it had to be considered as non-existent as evidence.
In other words, not that the DNA results obtained by Raf should be read to have identified Raf's DNA or not, but that the reading could not be considered as evidence because it was only a single run.
Marasca also faulted the length of time before the bra clasp was recovered, and the fact that it was passed around with visibly dirty gloves. (I'm not sure if Marasca also pointed out that Stefanoni destroyed the clasp through improper storage).
The issue of whether Raf's DNA, even if present, would have been an indication of his presence at the crime scene, at the time of the crime, is a separate issue. IIRC, Marasca did note that DNA cannot be attributed to have been deposited at a specific time or by what means, and emphasized the burden of proof is on the prosecution to prove its results are valid, and not "contamination must be proven".
Very troubling to me though, is its unclear to me that if Marasca had concluded Raf's DNA was on the bra clasp, or if Amanda's DNA had been innocently deposited in the room, with no other supporting evidence of any kind as is the current case, could Marasca have upheld the conviction?
As I've said, I think Amanda and Raf were very, very lucky to get out of this fraudulent case. Misseri and many others I fear are still trapped.
You do a great job of explaining things, and its only my own frustration at not being able to always follow that I'm reacting to. The cure of course, is to do my own homework.