Sunday, May 5, 2013

3. The Meredith Kercher Case - Back to the Drawing Board (Part Three)

Huh! There's gotta be some contamination somewhere!


I started out this new series because the Italian Court of Cassation recently quashed the Appeal Court's acquittal of both Amanda Knox and Raffaele Sollecito.

In Part One, I discussed the break-in, the Appeal Court's findings on this and the possible way in which the Court of Cassation might have viewed that court's findings. In Part Two, I discussed the DNA evidence with regard to the so-called "double-DNA" knife, again attempting to guess what the Court of Cassation made of the Appeal Court's decision on this matter.

This time around, I'll be looking at the DNA evidence with regard to the bra clasp. After that, I'll make a few remarks concerning the possibility of the DNA results deriving from contamination.

The bra clasp

Just to re-iterate: the experts appointed by the Appeal Court maintained that (a) it is not clear that the DNA found on the clasp was attributable to any handling of the clasp by Sollecito, (b) it is not clear that it actually was Sollecito's DNA in the first place, and (c) the DNA could be the result of contamination.

As I did when discussing the knife, I'll focus on the central tenet of this argument: it isn't clear that the DNA found belonged to Sollecito. However, I'll start with the experts' first point: it isn't clear that Sollecito's DNA derived from his handling of the clasp.

My remark here is quite similar to the one I made when it came to the knife, and the notion that it cannot be established that Kercher's DNA (as found on the knife) was derived from blood. The experts' comments may well be correct, but are essentially meaningless. That it can not be established that Sollecito's DNA was due to his handling of the clasp in no way excludes the pertinence of his DNA being present in the first place.

So, on to the real question: was Sollecito's DNA actually found on the clasp? 

Well, the experts - and, subsequently, the Appeal Court - place a lot of emphasis on the fact that the DNA sample on the clasp was "mixed". That is: the sample contained the DNA of more than one person. The "major contributor" to the DNA was obviously Kercher herself, but besides hers, the DNA of at least one other person was present.

According to the original Court of Assizes, that person was Raffaele Sollecito. However, the experts dismissed this, insofar as they rejected the notion that the sample contained only the DNA of Kercher and Sollecito. Instead, they maintained, the DNA was that of Kercher and furthermore pointed to several males, one of whom could, indeed, be Sollecito.

Now, in itself, such an assertion may seem rather innocuous.  The question is not, after all, whether "other males" ever touched Kercher's bra; the question is whether Sollecito's DNA was present. And it would appear that the experts are at least partially acknowledging that it could well be Sollecito's DNA.

However, this part of the report has lead to rather surprising results. Firstly, it allowed the Appeal Court to not just repeat the same views on proper procedures and protocols that it had already made in the case of the knife, but to elaborate on them. "Therefore," the Appeal Court says at one point, "(...) it is easy to understand that when a mixture is present (a sample with several contributors) the problem of tracing a specific profile – that is, of identifying the peaks to pair in the graph, distinguishing them from those which are irrelevant and from other pairings – is particularly complex, since it is very often not possible to exclude alternative but equally plausible pairings."

In other words, the Appeal Court felt that the Scientific Police failed to act properly, not adhering to the (even stricter)  procedures and protocols applicable in the case of mixed samples. Hence, the result obtained is unreliable.

At this point it could be noted that the Appeal Court falls into the same trap as it did when it came to the knife: it does not look at this particular case and then try to determine the reliability of the test on the basis of the specifics of all the relevant factors involved; instead, it holds this test up to the general standards, as generally accepted by various experts in the field. The gap I pointed out when discussing the knife returns, perhaps even more strongly, here.

Rather astonishingly, though, the Appeal Court's reasoning does not end here. It furthermore takes a number of remarks of one the experts (as made before the Appeal Court orally) into consideration. After the deliberation quoted just above, it goes on to say: "And this is why Prof. Vecchiotti [one of the experts] was able to say that it was fundamentally possible to identify anyone’s profile in the graph obtained from the Scientific Police, even her own."

At first glance, I must admit, this view would seem to be quite nonsensical. I readily admit I have little specific knowledge of DNA or the way in which it is or should be tested, but the idea that the testing done by the Scientific Police was so shoddy (or, perhaps, that the DNA sample was just so contaminated) that basically anyone's DNA could have been obtained seems to me to be quite incredible.

What the expert, in her oral testimony, probably meant to say is that, since this is a mixed sample, various bits and pieces were found in the results that could, in theory, be combined in a great many different ways, thereby procuring the DNA profile of a variety of possible (that is: theoretical) people. However, such a remark, if made, would seem to be somewhat misleading. Ultimately, it will of course be up to the person interpreting the results to decide if a person's DNA is or is not actually present, but the interpreter will certainly, first of all, need to find a full profile (bits and pieces are insufficient). Sollecito's full DNA was found in the result (as the experts expressly acknowledge); besides Kercher's, no-one else's DNA (that is: a full profile of DNA) was found. In theory further DNA profiles could also be put together that would lead to "someone else", but that person would be purely hypothetical: he or she would simply not exist. The only way to get around this - to nevertheless find the DNA of an actual person - would seem to be to accept a less than full profile; to just use, in other words, some bits here and some pieces there. This, of course, the Scientific Police did not do, and neither would anyone else, including the experts.

All this is, I would guess, what the expert was referring to. However, the Appeal Court seems to have misunderstood her, and thereby quite possibly have totally misrepresented the experts' actual findings.


After having remarked on the reliability of the DNA test result, the Appeal Court quickly moves to the issue of the possible contamination of the sample. The court deliberated similarly with regard to the knife, so the issues regarding contamination can best be discussed together.

There is a preliminary remark to make here, though, and it's an important one.

When I talk about contamination, I am not talking about the reliability of the DNA sample itself. What I am talking about is the question of whether the sample, though reliably attributable to a single person, should nevertheless be disregarded due to the fact that it existed where it did due to contamination.

An example may explain this. A sample may well be severely impaired due to, say, bacteriological damage. It may then become difficult to ascertain whether or not a match can definitively be made. You could, in such a case, say that the sample had been "contaminated" by bacteria. However, that is not what I'd understand the specific term of "contamination" to mean. Alternatively, you could have a perfectly fine sample, and yet have to dismiss it because, simply put, the DNA could very well have been inadvertently placed there by a police officer wearing dirty gloves. Now that, in my book, would be contamination.

I mention this because the distinction I make does not seem to be the same distinction made by the experts appointed by the Appeal Court. Indeed, I am not quite sure what definition of the term the experts are actually using; theirs seem to be a somewhat imprecise term. (To be fair, though, my own interpretation may seem practical, but could well be a little dodgy scientifically!)

Having said this, though, I must immediately remark on a clear flaw in the experts' report. The report extensively deals with contamination in general, and the possibility of contamination having happened in the laboratory of the Scientific Police in particular. However, it seems the experts were unaware of the fact that the Scientific Police employed certain "negative controls" during their handling of the samples in the laboratory, and the use of these controls greatly decreased the risk of any contamination having taken place there. To put it somewhat more simply: it seems as if one may reasonably disregard the remarks made by the experts concerning the serious possibility of contamination having taken place inside the laboratory.

What we are then dealing with is the question of whether anything went wrong during the period before or during the collection of either the knife or the bra clasp, and up to the moment the two exhibits entered the lab. What we are talking about, therefore, comes much closer to my own definition of contamination.

So, did anything go wrong? Well, yes. Does this mean that the knife and the clasp probably got contaminated? Err, perhaps. Perhaps not.

Let's start with the knife. The knife was found by a police officer in Sollecito's apartment. The officer looked in a drawer in Sollecito's kitchen, saw this shiny knife, and apparently thought "Hey, this could be the murder weapon". He popped it into a bag and took it away. It was tested and, hey presto, it was the murder weapon. All this seems, to be frank, rather too good to be true (and, hence, one cannot help but be a bit suspicious), but it does not in any way indicate that the knife was actually contaminated.

After all, how could it have been? If the contamination didn't happen in the laboratory (and, as I have said, it seems that we must accept that it didn't) then how could Kercher's DNA have found its way onto the knife? The only answer would seem to be that, somewhere during the process of collecting the knife as evidence, someone who handled it had Kercher's DNA on his or her hands. However, there just doesn't seem to be any real possibility of that having happened (at least, not inadvertently, and therefore in good faith). Some possibility of contamination still remains, of course - you cannot, after all, rule out all theoretical possibilities - but it becomes quite implausible.

As for the bra clasp, the story is rather different. In my earlier series describing the original Court Of Assizes ruling (that is, The Verdict in Perugia series), I stated the now almost infamous fact that the bra clasp was not secured as evidence for some 47 days after the murder. Instead, it seems to have remained somewhere in Kercher's room. When it finally was procured, it was, perhaps, mishandled (picked up from the ground, dropped back down, and then picked up again, by officers who perhaps were wearing gloves already worn in a different room). Even worse, it was found in a different place than where it had been directly after the murder; somehow, it had been moved. Besides this, the experts, as stated above, found that the clasp contained not just the Kercher's DNA and that of Sollecito, but also the DNA of "other males". This certainly seems to be an indication of sorts that the clasp may well have been contaminated.

The question, of course, is how the Court of Cassation looked at this matter. 

To understand the this a bit better, though, you should first be aware of a legal issue that arises here.  That issue is simple: who has to prove what? The prosecution, perhaps not surprisingly, has argued that whilst it might need to prove the fact that the samples found on the knife and on the clasp were, indeed, those of Kercher and Sollecito, it need not prove the absence of possible contamination. The defence, on the other hand, maintained that discounting the real possibility of contamination was simply part of the prosecution's task of proving "without a reasonable doubt" that Knox and Sollecito are guilty.

This is, it should be said, very much the sort of issue the Court of Cassation is equipped to deal with, and, I would surmise, very much the sort of issue the that court has dealt with many times in the past. I would guess that its ruling in this case will not favour either the prosecution or the defence unequivocally. Instead, I suspect the Court of Cassation will have thought that it's a bit of both.

I would, more specifically, suspect that the Court of Cassation may state that it is the prosecution's task to full disclose any and all information with regard to any possible contamination (i.e., to state clearly and simply what the police did or did not do with regard to the knife and the clasp), and that it is then the task of the defence to establish whether, given the information provided, any real chance of contamination existed.

If that is just about right, I would expect the Court of Cassation may well have decided broadly along the following lines: the bra clasp was correctly disregarded by the Appeal Court;  the defence has adequately established that a very real danger of contamination existed. The knife, however, cannot be considered contaminated; as such, the Appeal Court's decision cannot stand, and this will be a matter that the new appeal court will have to take up again. 

Again though, there are all sorts of other permutations possible. And once more, we'll just have to wait and see.

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