Knox/Sollecito DNA battle – who won?

Giuliano Mignini and Carlo Torre

Prosecution advisor Giuliano Mignini and defence expert Carlo Torre in court today. Picture from

As courtroom debates over DNA draw to a close, tweets and early reports from English language journalists in Perugia covey a mood that things are going in the defence’s favour in the appeal of Amanda Knox and Raffaele Sollecito against their convictions for the 2007 murder of British student Meredith Kercher.

Maybe there’s some basis for this, but I’m unconvinced. One possible reason for taking such a view might be a misreading of the thing that’s hogged the limelight in reporting over the last 48 hours. Yesterday, prosecution expert Giuseppe Novelli criticised Carla Vecchiotti and Stefano Conti, the scientists who conducted a review of DNA evidence, for their decision not conduct a full re-test with regard to the kitchen knife alleged to have been used in the murder. According to Novelli, this could have and should have been done. It was an inexplicably missed chance to confirm the validity of the original testing.

Today in court, the prosecution formally requested further testing of the knife, but the request was declined. My impression is that some have taken this as a significant clue as to the thinking of presiding judge Claudio Pratillo Hellmann. But I don’t think it is. Whatever is between his ears, he was never going to accede to the request. Knox’s lawyer Luciano Ghirga objected in court that holding a second review of DNA evidence is virtually unheard of, and I don’t doubt that this is correct.

And re-testing wouldn’t have had much value in any case. If it had failed to find the DNA, that would not have excluded the possibility that there was DNA there at some point. And if it had found the DNA, that would not have excluded the possibility that it got there by contamination, as the defence have argued. The prosecution were sensible not to miss an opportunity to demonstrate with intent how confident they are about the validity of the evidence, safe in the knowledge that their bluff was never going to be called. But the inevitable rebuff means nothing.

It’s not easy to predict what the bench will end up making of the DNA evidence overall. That’s partly because the answers they are looking for are in the boring technical detail gone over by the experts in court, much of it obscure and most of it unreported. But, with regard to the knife, assuming they follow the explanations of the science they have heard in court, I don’t think the judges have much option but to accept that it is valid evidence.

Six weeks ago, it was another story. The possibility that the knife was contaminated was the ace in the defence’s hand. The DNA review said it was possible and it was not easy to see how any reasonable scientist could disagree. The quantity of Kercher’s DNA found was tiny and, unless everything was done extremely carefully, a tiny amount of DNA in a test can be the result of contamination.

There was never a real chance that this contamination could have occurred during the recovery of the knife, because this had happened at Sollecito’s flat, where Kercher had never been, and there is no good reason to think that her DNA might have been there. But the DNA review reported a lack of detailed information about how tests were conducted in the lab. So, unless the prosecution were able meet the burden of showing that everything in the lab was hunky dory, prudence dictated that the possibility of contamination there could not be ruled out.

That picture flipped in testimony on 30th July, when one of the authors of the DNA review, Carla Vecchiotti, was asked about the difference it might make if it could be shown that no material relating to the Kercher case had been tested in the lab during the six days prior to the testing of the knife. That could rule out the possibility of any of Kercher’s DNA being present in the lab in order to contaminate the knife. Vecchiotti said that six days was long enough for this to be the case. Perhaps tellingly, the defence don’t seem to have put forward any counter-argument to this.

Which means that the defence case with regard to the knife is effectively reduced to the proposition that the DNA sample was too small and some of the peaks in the printouts were below 50 RFU in height. It is what is sometimes referred to as “low copy number” DNA. But the argument is weak without the possibility of explaining a consequent risk. There’s no doubt that the sample is a match to Kercher and if there’s no possibility of contamination, who cares how small the sample was? And why should they? This line of defence seems to amount a plea to turn back the scientific clock. As DNA analysis has improved, it has become routine around the world (with the notable exception, until recently, of the US) for convictions to be based on tiny quantities of DNA. It happened in the Anna Lindh case, the Peter Falconio case and, in the UK, over 500 cold cases have been reopened using low copy number DNA evidence. The judges in the Kercher case ought really to treat the idea that the sample is too small in the same way they would treat a plea for a speeding ticket to be thrown out because it was printed in 6-point font.

Arguments regarding the clasp from Kercher’s bra, said to have had Sollecito’s DNA on it, appear slightly more finely balanced. The same principle as in the case of the knife would appear to rule out the possibility of contamination in the lab. But the judges fact a genuine dilemma when they consider the possibility of contamination at the scene of the crime. The prosecution point out that Sollecito’s DNA was only found in one other place in the flat, so it’s not as if the place was swimming in it. And there’s no real reason for it to be found in Kercher’s bedroom, which is where the clasp was recovered from.

But, whilst it may be true that the chances are not high, the question for the judges is how high do they need to be? That’s very subjective. They’ve been played a DVD showing various alleged breaches of protocol by investigators in handling evidence, such as failing to wear the right protective clothing and putting some of the evidence into plastic bags rather than paper ones. They also have to consider that the clasp moved across the floor of the bedroom between its discovery and its eventual bagging over a month later, by some means that has not been accounted for. These things don’t necessarily carry with them a huge increase to the risk of contamination. But the judges might just feel that the risk doesn’t need to be huge to be significant.

It also has to be acknowledged that, whereas there remains a considerable amount of evidence against Knox with or without the knife, the clasp is a fairly big part of the case against Sollecito. I don’t think he’s likely to walk free, but maybe it isn’t unimaginable.

And it seems that lead prosecutor Manuela Comodi has enough imagination to conceive of the possibility that the case may not go her way. On the one hand, this only seems like stating the obvious. But something seems wrong with any picture than involves a lawyer being candid with journalists.

Closing arguments begin on 23rd September.


9 Responses to Knox/Sollecito DNA battle – who won?

  1. Claude says:

    “the clasp is a fairly big part of the case against Sollecito. I don’t think he’s likely to walk free, but maybe it isn’t unimaginable.”

    Elaborate please. What does it mean for Sollecito if the clasp goes.

    • maundy says:

      Hi Claude.

      There’s a bloody footprint in the bathroom. The first trial reached the conclusion that this was consistent with Sollecito so as to be valid evidence against him, but not strong enough to actually identify him. Assuming the appeal judges feel the same way, that evidence is much weaker if there is nothing else of a physical nature (i.e. no bra clasp) linking him to the scene. There’s a witness sighting of K&S on the night of the murder. That witness was re-heard by the appeal, and seemed confused about dates. I think that testimony will still stand up, but its impossible to be sure. S wrote a diary/letters in prison where he keeps changing his story in terms of whether or not he can account for K’s whereabouts at the time of the murder. Very suspicious, but enough to convict? His failure to talk about this in court can be taken into account, though, and I think that’s quite a strong indicator of guilt. And, of course, the knife links him to the crime because it was found in his flat. But that doesn’t necessarily mean he knew what it had been used for.

      Overall, I think it may be touch-and-go without the clasp. But I also think the clasp won’t be disregarded.

  2. jar says:

    There is also Guede’s testimony that Sollecito was there.

    May I take this opportunity to say how much I have admired and appreciated your precise and rational summaries during the various stages of this appeal.

  3. Naseer says:

    Hi Maundy,

    Thanks for your lucid summation. At this point I’m glad the court’s moving past the overemphasis on the knife and bra clasp.

    There were at least two other assailants that night besides Rudy Guede. Amanda Knox and Raffaele Sollecito best fit the bill.

  4. Sara says:

    Hello Maundy,

    I came across your site by chance today and have been reading every post of yours multiple times over the last few hours. I am really glad to have finally found someone who has given honest, unbiased, knowledgeable and objective reviews.

    I think that the footprint, the change-a-minute stories of RS including the one about him having cooked with Meredith previously and Guede’s testimony placing him at the scene of crime may cast sufficient doubt about his innocence, despite the bra clasp contamination theory. Also, since him and AK seem to be corroborating each other’s stories (atleast to an extent), it doesn’t seem realistically possible that one of them is involved while the other isn’t.

    However, there is something which has been baffling me since the beginning and I thought you might be able to explain this to me. How is it possible that Guede’s faeces was found in the bathroom of the flat if it 3 of them attacked Meredith together. It doesn’t seem probable that he decided to use the bathroom in the middle of the attack. Neither does it seem possible that he decided to use the bathroom first before they attacked Meredith while the other two waited. If the three of them arrived at the flat before Meredith and he decided to use the bathroom while they were waiting, why did he not flush the toilet? Surely, he wasn’t that anxious to commit a murder that he ran out as soon as he heard her arrive? Or, if I presume he did so after the murder, then why are his bloody footprints there in the other bathroom, could’t he have washed himself up in the same bathroom? I really cannot imagine a scenario which would lead to this other than the one Guede himself is claiming, I hope you will not think me stupid and explain this.

    • maundy says:

      Hi Sara and thanks for your nice comments.

      On the question of the poo…

      According to Guede’s story, he was on the toilet when Meredith was attacked, those contemplative minutes being interrupted by the sound of a scream. So, even though I don’t think there is any case, on balance, for Guede’s innocence, it has to be noted that his is the only account that gives a proper explanation for the poo.

      For either the likely prosecution case in the appeal (that the three of them conducted the attack together) or the likely defence case (that Guede was a burglar and carried out the attack alone), you have to suppose a few things in order to accommodate his number two. Firstly, Guede must have been in the flat for a while – whether invited or uninvited – before the murder happened, because the alternative is that he decided to take a dump either during the attack or after it, which seems implausible. I’d say that’s not too difficult in either case to accept that Guede could have been there an indeterminate amount of time. Secondly, Guede would have had to simply be the type of person who sometimes doesn’t flush. AFAIK, no witness testimony to that effect has ever been introduced. However, it is true that sometimes some people don’t flush. Thirdly, he would have needed to have either had no opportunity to flush after the murder or have been in too much of a panic to think of it. Those things also seem quite plausible.

      A thing you are factually wrong on – there was no physical evidence of Guede in the other bathroom, only Knox and Sollecito.

      • Allison says:

        Hi Maundy, I’ve always thought it strange that Amanda didn’t flush it away when she noticed it [when she went in to dry her hair]. Instead she left it there – for the police to find I’m sure…


  5. Sara says:

    Thank you Maundy for trying to explain this to me. I suppose there are so many nutters in this case that anything is possible. I guess what is bothering me is the fact that while it is easy enough to accept the defense’s arguments in this particular scenario, it is far more difficult to accept the prosecution’s theory. Yet, so many other prosecution theories seem to make sense compared to defense. I mean, in this particular scenario, the defense claims that Guede broke into the house, decided to use the loo and while he was finishing his business, Meredith came into the house so he just got up and walked out to confront her or whatever. Seems plausible. Whereas if we consider prosecution’s theory, we have many other complexities. If we assume that Guede was alone in the flat for a while, then how did he enter? If we suppose he broke in, then it means that the break-in was not staged. Let us say he was not alone but all three of them arrived together. Did he decide to take a loo break while the other two assaulted Meredith? Or did the other two decide to assault her on their own while he was in the loo and he simply helped them when he heard the scream? In that case, it makes Guede almost innocent of the actual crime. Also, in either case, when did he get the time to sexually assault Meredith as according to Nara’s testimony, sounds of running footsteps were heard almost immediately after the scream. Too many things seem rather unlikely. The only explanation that makes sense to me is that Guede is atleast partially telling the truth (which might also explain his reluctance to help the prosecutors because they did not “trust” him). However, if we consider that as true, then it means that he indeed heard a scream and in that case, when did he get time to deposit his sperm inside Meredith before bolting off? Or were the screams that Guede and Nara heard different?

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