The case of Robert Kennedy

August 31, 2011

Arthur Eathorne, found murdered in his flat in 1990

In a recent Australian TV magazine feature on the Meredith Kercher case, the British journalist Nick Pisa said something I found a little odd. In his view, it seems, the case would never have come to court had the murder taken place in the UK, because the evidence is just insufficient.

Now, there are worse things in the world than being a little chauvinistic about standards of justice. But I don’t think that’s exactly what’s going on here. Many people who seek to defend Amanda Knox and Raffaele Sollecito do so, in my opinion, on the basis of a wholly unrealistic view as to how much evidence ought to be enough to convict someone in a court of law.

There’s a lot of evidence in this case. You only need to be able to to count to know that. Of course, for each item of evidence there’s a defence argument, with greater or lesser plausibility, that it doesn’t say what it might appear to say. But the whole purpose of taking the matter to court is to have those arguments adjudged. No prosecutor has ever dropped a case on the grounds that footprints found near a body which tests say were probably made in blood might actually have been made in fruit juice. Or that falsely accusing someone of a murder is a relatively normal thing to do if you are suffering from stress.

I thought I’d take a look at a British case which, in my view, was prosecuted on evidence which was far thinner than in the Kercher case.

Robert Kennedy is a former prostitute, convicted in 1991 of murdering a client. He has always maintained his innocence and has unsuccessfully appealed his conviction twice, the last time being in 2007.

The only physical evidence linking Kennedy to the scene of the crime, the victim’s home, came in the form of two cigarette butts. These were believed by police to have been left by the culprit because a taxi driver had called at the house a short time before the murder, and he testified that the ashtray in which the butts were found was empty at that time. The butts were not initially examined for DNA, but saliva on them was found to be of a type matching Kennedy and also matching about 25% of the population. This evidence was admitted at trial. Years later, the saliva was tested for DNA and it turned out not to be Kennedy’s, but that of an unidentified person.

The main evidence against Kennedy comes from two witness statements relating to a conversation that took place at Kennedy’s shared house. The first witness said that she walked into a room in the middle of a conversation between Kennedy and four other people. They were, according to her, discussing a murder that had happened locally. Since news of the murder had not yet broken in the media, it is unclear how they knew about it. The witness also recalled Kennedy mentioning something about an ashtray and then being told to shut up by someone else present. This is significant, because a large glass ashtray (not the one with the cigarette butts in) was missing from the scene of the crime and may have been the murder weapon. Witness number one also seemed unsure about whether the conversation had taken place on the day of the murder or the day before, but that does not seem prevented her testimony being accepted by the trial jury.

Witness number two was party to the same conversation, but did not hear the word “murder” used, only talk of some incident or other involving two men and a woman. She said that Kennedy had been told to “shut up”, but that this was not anything to do with him mentioning an ashtray. She couldn’t remember what night the conversation had taken place on. She also recalled seeing a pullover with blood-stains on it, but wasn’t completely sure whether that was on the same night.

According to the police, Kennedy had lied to them on two occasions. Firstly, he had at first denied, then later admitted, having had sex with the victim. I think it seems obvious that even an innocent person might have told that lie. Secondly, he told police that he had read in the newspaper that a large glass ashtray was missing from the scene (a fact that had indeed been reported in the media) and offered a description of it from his recollection, saying that it was oval and had a label saying “Hofmeister”. But enquiries with the makers of Hofmeister lager revealed that they had never produced an ashtray fitting the description given by Kennedy.

On remand, Kennedy had also been alleged to have confessed to three fellow inmates. One of these was applying for parole and had agreed with the police that he would try to get information for them by talking to Kennedy. A second was also applying for parole and told the police he had information about Kennedy but would not tell them anything further until he found out whether or not he was going to be released. A third had no parole hearing in process, but had given details about Kennedy’s alleged account of the crime which describing things which were known not to have happened. Kennedy’s story was that he had spoken to all three of the witnesses about his case, which is how they were able to concoct accounts for the police. But he denied having confessed to any of them.

The defence produced evidence that the victim had been wearing a wind-up watch which had stopped a certain time after the murder. Unless this was almost fully-wound when the crime occurred, Kennedy could not have been the murder, because he had a solid alibi.

Those are the facts of the case. It might seem to you like an enormous miscarriage of justice. After all, prisoners, particularly those who might be trying to bargain for a release, are not always reliable witnesses. The witness who heard Kennedy talking about a murder and an ashtray is clearly contradicted by another witness. And surely it is possible that Kennedy just made an honest mistake in describing the ashtray to police. Add this to the dispositive evidence in terms of the DNA and the thing about the watch, and there must be reasonable doubt. Mustn’t there?

I’m not saying any of that is wrong. But perhaps it makes incorrect assumptions about the normal standard of proof in criminal cases. Presumably, the jury heard and evaluated the witnesses, took the evidence before them into account and felt able to make a decision. “Reasonable doubt” is not the same as “no possible objections”.

In the Kercher case, as well as the DNA evidence which is currently the subject of debate, we have all the evidence of a staged break-in, footrprints made in blood (or, possibly, pear juice), Knox’s DNA found mixed with the victim’s blood, her false accusation that someone else committed the murder, two witnesses who saw Knox and Sollecito near the murder scene at times when they claim to have been elsewhere. Maybe the court will eventually decide that all the evidence was misleading. But the process is more-or-less the same as it would be for a British jury. How much do you trust the witnesses? How certain do you feel you need to be about the science? And, for prosecutors, the decision about whether to go to trial is mainly based on making a guess as to what the chances of conviction are, on that basis. I think the idea that all that evidence was never enough to even put before a court just doesn’t show common sense.

By the way, apologies to anyone who Googled in here expecting to find information about a link between Amanda Knox and the other Robert Kennedy.

R v Kennedy [2007] EWCA Crim 3132


Knox/Sollecito: How to spot a fake burglary.

August 8, 2011

In the ongoing appeal of Amanda Knox and Raffaele Sollecito against their convictions for the murder of Meredith Kercher in 2007, attention has recently been focussed on two pieces of evidence, a clasp from the victim’s bra and a knife, said by prosecutors to be incontrovertible proof linking the DNA of the two suspects to the crime. There will be more courtroom discussion about that in September but, as things stands, it does not seem easy to guess what the view of the court with regards to these two items will eventually be.

If the DNA from the knife and clasp proves resilient to assaults on its value, then it would seem likely that the convictions will be upheld. But what if that is not the case? Supporters of Knox and Sollecito will point out the central position of this DNA evidence within the prosecution case. Take it away, and what is left? Those who believe that Knox and Sollecito are guilty will argue in return that there is plenty left. This was never a case that hung by a single thread.

In a way, both sides may be right. Clearly, if you take away two pieces of evidence that, essentially, purport to show that Knox stabbed Kercher and that Sollecito removed her bra after she died, then the case against them can only be weakened. But by how much? Can the rest of the evidence stand up on its own, or has it always relied on the knife and clasp to hoist it out of the mists of uncertainty through corroboration?

Prosecution lawyers have said that, even if the current battle is lost, there is still DNA evidence, in the form of mixed samples from Kercher and Knox found at the scene, which they believe is equally compelling. But that is one of a number of possible views on the case. In the event that the knife and clasp go MIA, I wonder whether the best part of the prosecution case to deputise might be the question of whether Knox and Sollecito faked a burglary at the crime scene in an attempt to cover up their crime.

The day after the murder, police officers arrived at the flat where it had happened because two mobile phones used by Kercher had been found abandoned. When they arrived, Knox and Sollecito told them that they were concerned because their appeared to have been a break-in and there were spots of blood in the flat. A short while later, Kercher’s bedroom door was broken down and her body was discovered.

Investigators soon arrived at a belief that the apparent break-in was in fact simulated. This was, perhaps, the earliest indication that Knox and Sollecito were involved in the murder. Apart from Kercher, Knox had been the only person in town with a key to the flat. What’s more, it seemed unlikely that anyone else could have a motivation to interfere with the crime scene in the manner that had taken place. A burglary would draw attention away from the occupants of the flat, but from who else? And since the other occupants of the flat were not in town…

The potential power of a staged crime scene hypothesis is shown by a study conducted in 2000 by the forensic scientist Brent Turvey. This looked at twenty years’ worth of US criminal cases where a crime scene had been staged and attempted to identify commonalities between them. Although this turns out to be only 25 usable cases (all domestic homicides), what is striking is that in 11 of them, convictions appear to have been secured purely on the basis of police and expert testimony as to the staging. And in all the other cases, the additional support to this testimony came in the form of some sort of confession or self-implicating statement by an offender (which is relevant, because Knox made a statement accusing her boss of the murder and placing herself at the crime scene, which she later retracted).

This doesn’t provide a solid guide to the chances of the current appeal being upheld purely on the basis of the burglary having been staged, because Turvey is not able to tell us about the number of cases where there was an acquittal despite an allegation of crime scene staging. But it does give us an indication that such an allegation can be enough to sustain a conviction, provided a court buys into it. Neither DNA evidence, nor eyewitnesses, nor bloody footprints, nor phone intercepts, nor analysis of computer hard-drives are necessarily required.

In Knox and Sollecito’s 2009 trial, the court did exactly that. The appeal is hearing no new evidence on this question, but the judges are entitled to review the evidence from the trial and come to a different conclusion if they so wish. It may be that they have to do just that if the appeal is to be successful. But is that likely?


There is no single handbook that gives a definitive explanation as to how the staging of a crime scene can be established. But there does seem to be broad consensus among experts on a number of guiding principles.

Firstly, the question is, primarily and ultimately, concerned with physical evidence in the form of the state of affairs found at the crime scene. Experts differ as to how relevant non-physical evidence might be in certain cases, but it is clear that, with the obvious exception of a confession with regards to the staging, such evidence can only ever be vaguely indicative one way or the other.

The victimololgy of the case (essentially, does anyone benefit from the death of victim?) may be a consideration. But that does not seem to be relevant here. Another factor might be the existence of a potential suspect who has made attempts, apart from the supposed staging, to steer the attention of investigators away from himself (or herself). An example of this might be where a suspect has made a false accusation against someone unconnected to the crime…

But the final proof or disproof of staging is not in such details. It is in the physical arrangement of the crime scene.

There is a long-established view that the investigation into staging should focus not on attempting to prove it, but on attempting to disprove the competing hypothesis (in our case, that there was ever a genuine burglary). This may sound like a pedantic distinction and perhaps it is. But it is held to be important because it provides clarity of method. First you search for evidence which is inconsistent with the competing hypothesis. You then test these inconsistencies against all the known facts of the case. Can they reasonably be given any explanation other than staging? If any inconsistencies then remain, your conclusion must be that the scene was staged.

Perhaps I am labouring this point. But I’d remark that much Internet theorising in this area with regards to the Knox/Sollecito case focuses on explaining how a genuine burglar might have committe the crime, drawing attention to evidence that is consistent with that account: the position of a shard of glass or the way a rock appears to have landed in relation to the window.

I can understand the urge to do this – obviously is is useful to have an alternative to the account offered by the prosecution. But at the same time, it ought to be obvious why such approaches are problematic from a crime scene investigation point-of-view. People who stage crime scenes typically do everything they can think of to ensure that the staging looks as realistic as they can make it look. Therefore, any evidence that is consistent with a genuine break-in is also consistent with staging. You can only disprove the staging by focusing on the alleged inconsistencies. That is a one-sided approach, admittedly. But it is, apparently, the correct approach.

The inconsistencies

This book offer a three-point checklist as a starting point in identifying staged break-ins: were inappropriate items taken?; did the point of entry make sense?; did the hypothetical perpetrator have a high-risk of being seen?

The items removed from the flat, apart from the murder weapon or weapons, were: two mobile phones, later abandoned; Kercher’s bank cards; probably cash; Kercher’s house keys. The cash aside, it is not clear what value these items would have to a burglar. The phones, cards and keys of someone recently murdered are obviously very risky things to take from the scene. Perhaps it might be argued that our burglar didn’t realise that at first. But why the keys? Indeed, why was the door to the room in which the murder took place locked?

Point of entry is discussed below, but it suffices here to say that our burglar has chosen a particularly difficult, perhaps impossible, way of gaining access to the flat. The risk of being seen was also reasonably high. Although it was dark, the point of entry is on the part of the building most visible to passing pedestrians and traffic.

So, we seem to have a case which fits well with these recommended indicators.

This book provides a useful guide to the types of inconsistencies that might be looked for.

Point of entry

The hypothetical point of entry is the green-shuttered window at the top of this photo.

First we consider the point of entry. Specifically, we should be looking for anything that might have made the point of entry impassable (was it barricaded or bolted, for example?); what transfer evidence is apparent (e.g. blood, fingerprints, footprints etc); whether the entry could have been possible in the manner required to commit the crime (this is, we are told, “often the most dispositive feature” in establishing crime scene staging).

Our hypothetical burglar gained entry to the flat through a second-level bedroom window. It was not barricaded or bolted, but the outside shutters were firmly closed – the wood was swollen, so they were wedged in place. They might have been openable from the outside, if with a little difficulty. But this, it has been argued, would have required the burglar to make the ascent twice: once to open the shutters, then back down to the ground to hurl a rock at the window, then finally back up. The first climb would have been speculative – had the shutters been latched on the inside, that would have been the end of the attempt.

The window would also be a strange choice for a burglar on account of its position. It is in full view of the road that passes by the building and, as you can see from the photo, it doesn’t offer an easy climb. To the rear of the building is a balcony, which certainly looks more accessible and is relatively secluded. What can have been in our burglar’s head?

What’s more, no transfer material was found. No dirt or bits of leaves on the wall, no footprints on the bedroom carpet, no nothing. The burglar managed, so it seems, to perform the break-in without leaving a trace of himself.

The trial court was convinced that the window could not be considered a realistic target for a burglar. But, all the same, might the appeal court not see some room for doubt? It looks to all the world like an unlikely point of entry. But, surely, you can’t send two people to prison if there is even a slim chance that the break-in might not have been staged.

Man climbing up wall

Does this photo help the defence case or the prosecution case?

What the textbooks recommend is to perform a reconstruction experiment in order to give a definitive answer to the question. In other words, you get someone (maybe these guys) to attempt the climb. That’s something that investigators never did. Perhaps they felt that the impossibility of the exercise was obvious, or perhaps they didn’t want to risk a success. The defence, though, do seem to have conducted some sort of experiment, as shown by the photo to the right. But why were the results of this never discussed in court? Does the photo show someone succeeding in accessing the window, or failing?

The next relevant question, working through the list, is whether a weapon has been removed from the crime scene and, if so, why? At least one knife must have been used in the murder, but it was not found with the body. How consistent would this be with the actions of a burglar? I don’t think we can be entirely sure that it is inconsistent (after all, for all we know the knife may have been monogrammed), but maybe you have a different view.

Then there is a question of whether the body was moved after the crime was committed, or whether it was dressed or undressed to any degree. Kercher’s bra was found on the floor near the body. The cups were stained with blood on the front side, suggesting that she was wearing it at the time she was stabbed. The bra also bore tiny spots of blood, similar to spots found on Kercher’s chest, suggesting that she exhaled blood onto herself while she was still wearing the bra.

The body was found covered by a duvet, but blood from the body does not appear to have transferred to any great extent to the fabric of the duvet. This suggests that the blood had substantially dried before the body was covered. Our burglar must have hung around quite a while.

The defence argument is that Kercher must have been sexually assaulted after she was stabbed. That would make the motive for the burglary an especially deranged sex attack. Such things are not unheard of, but why would such a burglar waste time rifling through clothes in the neighbouring bedroom (which is what appears to have taken place)? And how does it explain the duvet?

It is also necessary to consider the ransacking. Our burglar seems to have rifled through clothes in the room of one of the occupants of the flat, paid some interest in her laptop, but not actually taken anything of value. Why was he interested in the clothes? What was he hoping to find? Why did he not, instead, go quickly from room to room picking up items of obvious value? Does the existence of an apparent ransacking fit easily with the defence supposition of a particularly unusual sex attack? If this was the motive for the burglary, why did the burglar not make straight for his intended victim? Or, if he decided to look for valuables after the attack, why did he take nothing?

Some glass on a window ledge

The glass on the window ledge

What would seem to be the most convincing evidence of a staging is, however, none of the above. It is all to do with glass. Broken glass was found on the window ledge in a pattern that was consistent with the shutters having been closed when the window was broken. That is, glass was found distributed on the ledge, but no further forward that would have been permitted by the shutters in their closed position.

Both the occupant of the room that had been “burgled” and one of the first police officers on the scene testified in court that they had found shards of glass from the window on top of the belongings found strewn across the room. How could this be possible unless the ransacking had occurred before the window was broken.

So there’s quite a pile of evidence to suggest that the crime scene was staged. How much of it can be explained away? I don’t know. But the difficulty for the defence is the logic of the methodology. If there’s one detail that can’t be reconciled with a genuine burglary, then there must have been a staging. That could be the glass on top of the ransacked possessions. If the appeal judges can’t think of a reason to doubt the witness testimony (I can’t, although that’s not necessarily a guarantee that they won’t), then there must have been a staging. And if there was a staging, Amanda Knox must have been involved in it.

Knox/Sollecito: update on today’s court proceedings

July 30, 2011

Amanda Knox and Raffaele Sollecito

Photo by Franco Origlia

The prediction I made at the end of my last post that today’s hearing in the appeal of Amanda Knox and Raffaele Sollecito would be “the most enlightening and important session” in the process turned out a little wide of the mark, mainly because the meat of the prosecution response to the recent DNA review in the case didn’t happen. We will have to wait until after the court’s summer recess for that, when police scientist Patrizia Stefanoni will give evidence explaining why, in spite of the criticisms in the review, the DNA analysis she undertook in relation to two key pieces of evidence in the case is reliable.

That will be the most enlightening and important session in the process. Mark my words.

Today’s hearing began with the presentation in court of a letter from Stefanoni’s boss, Piero Angeloni, taking issue with the DNA review and affirming his confidence in the work of his people. It might be said that this tells us little we didn’t expect – after all, it already seemed clear that the police were not going to put up a white flag. Apart from support for Stefanoni, though, I think the real purpose of the letter to highlight how unusual the DNA review undertaken in the case is, in the view of the police. It is unprecedented, says Angeloni, for the police to be subjected to this type of criticism in court.

I wonder if this is a foretaste of a public policy argument the prosecution may seek to hang their hat on. The authors of the review, Stefano Conti and Carla Vecchiotti, start from a position of feeling they need to trawl through academic literature in order to piece together the standards by which they feel Stefanoni should have operated. But, it might be argued, this constitutes them assuming the role of a two-person regulatory body. Even if their recommendations are sound, it is the accepted regulatory framework that matters. The courts cannot permit the police to be subjected to creative criticism that goes beyond this framework because, in that case, the streets would quickly fill with acquitted murderers.

At least, I think that’s where we may be going, and it is also something that is reflected in what Stefanoni recently said to the Observer: “We followed the guidelines of the ENFSI, theirs is just a collage of different international opinions”.

Given what is said the review though, the question that immediately raises itself is how closely the ENFSI or any other guidelines have been followed. I don’t know what the standards required would have been on the relevant date, but it is likely that Stefanoni will need to convince the court that, for example, negative control tests were appropriately carried out on the samples taken from the alleged murder weapon. Arguing that you only need to follow certain agreed standards and then going on to argue that you don’t even need to follow those may be a step too far.

Meanwhile, each side seems to have scored a point in their cross-examination of the experts regarding that alleged murder weapon, a knife recovered by police from Raffaele Sollecito’s flat. The defence were able to elicit an opinion that the blade of the knife had been subjected only to a fairly ordinary wash prior to its discovery by the police. The judges will no doubt be wondering how likely it is that Knox and Sollecito dealt with their murder weapon by giving it only a general clean.

The prosecution, for their part, secured an agreement from Carla Vecchiotti that a six-day gap between the testing of the knife and any prior testing of items containing the DNA of Meredith Kercher would be sufficient to guard against contamination. This may be very helpful to prosecutors, since their main task is to show that the theoretical risks of contamination outlined in the DNA review could not have given rise to any actual contamination.

With respect to the other piece of evidence under consideration, the clasp from Kercher’s bra, said by prosecutors to bear Sollecito’s DNA, the most important answer may turn out to be one that wasn’t given. According to one report, when asked by prosecutor Manuela Comodi how it was possible that Sollecito’s DNA on the clasp could be the result of contamination, the two experts were not able to give any clearer explanation than “anything is possible”. That answer could well turn out to be an Achilles heal for the defence case.

Knox/Sollecito appeal hearing on 30th July

July 29, 2011

Barring delays, overruns or surprises, tomorrow should see the last hearing in the appeal of Amanda Knox and Raffale Sollecito before the court goes into summer recess.

On Monday, the court heard scientists Stefano Conti and Carla Vecchiotti give a rundown of their review of some of the DNA evidence in the case. They did this with the aid of a DVD containing crime scene footage, designed to illustrate flaws in police procedure in the collection and handling of evidence, but without being questioned by the prosecution or defence lawyers. This means that the likely points of contention in relation to the review have still not been gone into and, for information about that, I refer you to my previous posts here and here.

There have, however, been two developments reported in the Italian press which may stand some sort of chance of having some sort of impact on proceedings.

The Umbrialeft website is reporting that the above-mentioned DVD played to the court by Conti and Vecchiotti on Monday has since been subjected to a court order effectively stating that it forms part of the proceedings. The report is less than clear, though, as to why this event is newsworthy. My best attempt at inter-linear decoding says that what has gone on is that the prosecution have asked for a copy of the DVD and presiding judge Hellmann has then issued the order so that they might be entitled to a copy. This would just be an administrative tidying-up in relation to something that should really have been done during the court session.

However, I appreciate that this version is irritatingly probable and mundane, so here’s a different take. Francesco Maresca, lawyer for the family of Meredith Kercher, has recently been complaining to reporters that the DNA review does not appear to have been written from a disinterested standpoint. And, in last Sunday’s Observer, an unnamed police source went further, suggesting that the experts were being “fed information” by the defence.

Now, it’s all very well for lawyers and police officers to have suspicions about the integrity of the experts, but it’s not much use to the court without evidence. So, suppose that someone paying attention to DVD presentation on Monday noticed that it contained material which did not seem to have been supplied to the experts by the court. That might be prima facie evidence of undisclosed communication between the experts and the defence, or someone close to the defence. If those circumstances were to arise, the bench may well feel obliged to disregard the DNA review.

But let’s not get carried away. The simplest explanations are usually the best and, let’s face it, were the experts crooked they would surely not make such a basic error. Still, you never know…

Meanwhile, there has been a surprise twist regarding the evidence of Luciano Aviello, the gender-nonconformist Mafioso who testified a few weeks ago that the killer of Meredith Kercher was in fact his fugitive brother. At the time, this was more or less as obvious a lie as it is possible to imagine, particularly given Aviello’s record of eight separate convictions for criminal defamation and the fact that the court heard another witness claiming that Aviello had been offered a large some of money by the defence in return for his false testimony.

So, in the face of a police investigation into this claim, Aviello now says that he was offered €30,000 (which he intended to spend on a sex change operation) by the Sollecito family and with the knowledge of defence lawyers. Quite a price-tag for the worthless garbage they got in return, but maybe the Sollecitos have better money than judgement. What is more, Aviello now claims that Sollecito confided to him in prison that Knox, but not he, was responsible for the murder.

The main reason this is unlikely to have a major impact on the appeal is that, in the absence of corroborating evidence, Aviello is clearly no more reliable as a witness than he was a couple of weeks ago. The court will need to take account that his original tale, obviously and plainly false in any case, has now progressed to being plainly and obviously false. Prosecutors will need to decide whether it is worth pressing for him to testify again. Given that there exist more credible allegations as to the dirty hands of the Sollecito family, they may wish to add pressure on the bench to wonder if there might be an iceberg below. On the other hand, they may feel that the judges and juror-judges already have the information they need, and that it would be a mistake to draw attention away from the much more important matter of their rebuttal to the DNA review.

As a side-note, something that seems clear from the reporting of this story is that Aviello and Sollecito associated with each other in prison, at least according to Aviello. But, as far as I can tell, this rather material bit of information was not mentioned in court when Aviello testified on 18 June. Surely this is something that must have been known to the defence?

Regardless of whether any of these side-stories make it into the courtroom tomorrow, it promises to be the most enlightening and important session in the whole appeal. It won’t be possible to tell immediately whether it has been decisive but, for the prosecution, a lot hangs on how convincing or unconvincing their response to the DNA review turns out to be.

Knox/Sollecito DNA showdown: an overview (part one)

July 22, 2011

This Monday, 25th July, will be the most significant date so far in the appeal of Amanda Knox and Raffaele Sollecito against their 2009 conviction for the murder of Meredith Kercher. The court in Perugia will begin hearing arguments about two pieces of disputed DNA evidence on which doubt has recently been cast by a review. These arguments are likely to stretch over a number of hearings and travel into the intimate details of DNA analysis and the investigative process in the case. It would be misleading to suggest that we will know the outcome of the appeal just on the basis of this group of hearings. On the other hand, more will rest on the relative strengths of the defence and prosecution arguments in respect of these two pieces of evidence than on anything else that has been, or will be, discussed in court during the appeal process.

The DNA review in a nutshell

Stefano Conti and Carla Vecchiotti of the Sapienza University of Rome were asked by the court to review DNA evidence relating to a knife, allegedly used by Knox to stab Kercher, and the clasp of a bra removed from Kercher’s body after she was attacked.

On the basis of a number of factors, Conti and Vecchiotti take the view that the amount of Kercher’s DNA found in the sample taken from the blade of the knife is so low that it should be classified within a bracket known as Low Copy Number (LCN). This being the case, particularly rigorous procedures should have been applied in the handling of the knife by investigators and during the laboratory analysis of the DNA sample. Conti and Vecchiotti take the view that procedures at the crime scene did not meet these standards. They say they are not able to comment on the general standards in the laboratory, but they note that a number of measures that could have been taken to provide reassurance about the possibility of lab contamination were not.

They looked at two DNA printouts relating to the bra-clasp, one reporting the autosomal DNA of the sample taken from it (i.e. a standard DNA matching test) and one reporting details about the makeup of the y-chromosome content of the DNA. In both of these printouts, they identify peaks alongside those relating to Sollecito and Kercher which, although dismissed in the original testing as noise, they feel ought to be treated as genuine alleles, that is, as representative of real DNA information in the sample. There are a number of possible explanations for the presence of such additional DNA, but the authors of the review suggest that the possibility that these are evidence of low-level contamination of the sample cannot be ruled out. And, if contamination of the sample cannot be ruled out in general, then contamination of the sample with the DNA of Raffaele Sollecito also cannot be ruled out.

Clearly, these findings are good news for the defence. But the big question is how they well they will withstand scrutiny in the courtroom.

In my estimation, at the time the legal teams begin their arguments, the cards will be stacked in favour of the defence with respect to the knife. Specifically in relation to the question of contamination in the lab, the logic of the review is compelling, as I outlined in this post. If the knife is to be kept in play as evidence, then the onus surely falls on the prosecution the show that the risk of contamination was substantially mitigated by the strength of the procedures in place during laboratory analysis.

In contrast, I think the prosecution will walk into the courtroom with the upper hand as far as the bra-clasp is concerned. The court may be impressed by what Conti and Vecchiotti have to say to the extent that it will agree that contamination ought to be taken seriously as a possibility. But, in order to disregard the bra-clasp as evidence, the theoretical possibility of contamination may not be enough. The court will also need to be persuaded that contamination should be seen as plausible in practice, given the facts of the matter. And, in this respect, the review is weaker, appearing to offer only hypothetical and, arguably, not particularly likely-sounding accounts of how it might have taken place. So, a key task for the defence will be to try to paint a more vivid picture of this for the court.

That’s my view. But there are no foregone conclusions here. What I think it might be possible to discern, though, is the nature of the questions that the court will need to get answers to in order to come to a conclusion about these two troublesome pieces of evidence.

Coming up in the next post: key questions for the court

Was Casey Anthony’s DNA on the bra-clasp?

July 20, 2011
DNA readout from bra-clasp in Kercher case

Click on the image for a larger version

In 2009, the journalist Baribie Nadeau mentioned something in an article which many people will have wondered about when they read it. She said that Vincenzo Pascali, a scientific consultant for the prosecution in the early days of the process, had “hinted” that a sample taken from the bra-clasp of the murder victim Meredith Kercher had contained the DNA of not only Raffaele Sollecito but also his alleged accomplice in the crime, Amanda Knox.

It may be thought unlikely that there was much in this. That’s not to impugn Nadeau’s journalism – if a DNA expert hints at something like that then it is worth reporting. At the same time, though, you would think that, if Knox’s DNA really were present on the clasp, the prosecution would have mentioned it by now.

Nevertheless, given the information that is now available about DNA evidence in the case, I thought it would be worth looking into this suggestion.

The first thing to note – and it’s an extremely important thing to note – is that the DNA of Kercher and Sollecito found in the sample from the clasp accounts for either all or very nearly all (depending on which expert you are listening to) of the alleles observed. Since there is so little left to play with, trying to make a further DNA match out of it would seem at bit like looking at a nine and a six and wondering whose phone number in particular they might form part of. Completely impossible, even if you believe that further DNA might be present. Impossible, that is, using any method that is generally considered scientifically reliable.

What you could do, though, is lower your standards and begin to look at peaks that would ordinarily be ignored on the grounds that they could well be nothing more than noise. This makes the peaks that you are including less reliable (how much less reliable depends on how radical you are in including smaller peaks), but it might be argued that there is a legitimate trade-off. If you can get a very good match, then maybe it can be argued that a questionable peak here or there is acceptable. After all, how likely is it that the noise has simply been kind enough to appear in the exact places you would need it to in order to make you incomplete match complete?

So, you can see on the image that I’ve added green dots to the DNA profile taken from the bra-clasp, indicating the places where Knox’s alleles would be expected to be located. And it turns out that it is possible to see a fairly good degree of compatibility with the sample. But I had to go all the way and include even the tiniest bumps on the printout. Because some of these are so small that no numerical information about them is included, I also had to judge a few of the locations by eye (the blue numbers on the image indicate where I did this). This raises the additional problem that my own human error may have some effect on the reliability of what I have done.

But how strong is the actual match? Well, first you have to explain away two things. At loci D8S1179 and D19S433 (the first and tenth groups of peaks on the image), there are small peaks which the DNA review says are above the threshold where we can be confident they are noise. But they are only above the threshold by a hair’s breadth. So maybe we can consider the possibility that they really are noise. Then at locus D7S820 (the third group of peaks in the image), there’s location where you would expect to see an allele relating to Knox, but there is nothing there. Again, maybe this is not so much of a problem. We’re presumably dealing with an extremely faint DNA trace. Maybe it’s simply the case that just one peak out of 29 is so faint as to not be there at all.

What’s starting to emerge, though, is the problem with not having any real standard to go by in terms of which peaks you consider to be real and which you don’t. The judgements you have to make in order to determine whether there is compatibility or not start to become fairly subjective, at least in this case. At each locus point, the ways in which compatibility could arguably be ascertained are numerous, so things are different from how they were in considering the matches to Sollecito and Kercher. Whereas their profiles are quite clear and match 100% to unquestionably genuine alleles on the graph, it seems like you can pretty much see Knox’s DNA profile in the printout according to how much you want to.

A commenter suggested adding dots for a sample known not to be connected to the case. I thought this was a good idea, and whose DNA profile could be more suitable for the task than that of Casey Anthony, recently acquitted of murder in the US? So I’ve added her alleles using pink dots.

I think this goes to further illustrate the problem. Although there are a greater number of problematic spots on the graph that you need to ignore if you want to make Anthony’s DNA fit, some things go the other way. For example, 69% of Knox’s allele’s pair up with peaks on the graph that are above 50 RFU in height (one measure of a potentially genuine allele). It may sound from that like Knox’s DNA is beating the odds. But Anthony’s DNA profile, on the other hand, matches to those >50 RFU peaks 75% of the time. For me, it seems hard to see how you could justify being confident that Knox’s profile is there without also thinking that there is a least a decent chance that Anthony’s could also be there.

Then again, it’s always possible that I have it backwards and that, in reality, the bra-clasp printout offers a new chance for that half of America outraged by Anthony’s aquittal to get her back in court.

Knox/Sollectio: was the knife contaminated?

July 9, 2011
The Qubit Fluorometer

The Qubit Fluorometer, used in DNA analysis relating to the alleged murder weapon

One of the two exhibits in the trial of Amanda Knox and Raffaele Sollecito to be looked at by Stefano Conti and Carla Vecchiotti as part of their review of DNA evidence in the case is a knife, recovered from Sollecito’s flat and alleged by prosecutors to have been used by Knox to stab Meredith Kercher in the neck.

Conti and Vecchotti agree with the opinion of the chief police scientist, Patrizia Stefanoni, that Knox’s DNA was present on the handle of the knife and they don’t dispute the match between the DNA found on the blade and that of the victim. But they raise clear concerns that the DNA profile observed in relation to the blade could have been the result of contamination.

The reasoning behind this turns on their characterisation of the the DNA sample from the blade as “Low Copy Number” (LCN), essentially meaning that there were so few examples of the DNA in question within the sample that, according to mainstream scientific opinion, special measures would have been required so as to ensure the integrity of the testing.

In her trial testimony, Stefanoni appeared to accept the proposition that the sample in question may indeed have been an LCN sample. It appears difficult to be absolutely sure about this, because there is no accurate record of the quantity of originating material (Stefanoni has said it was “in the order of a few hundred picograms (pg)”). Quantifications during a process known as qPCR, it seems, would have given a strong indication, but there is no record of these having been performed – perhaps because of the very fact that the sample was so small as to be out of the range of sensitivity offered by the equipment that would have been used.

However, the review highlights two reasons to suppose that the sample must have been of an LCN-type quantity. Firstly, there are what are known as “peak imbalances” in the graphical representations of the DNA which were produced. In most graphical printouts of DNA tests, peaks come in pairs. In an imaginary perfect test, the pairs would all be of equal height to one another. That is rarely the case in practice, so a ratio of 3:5 is normally considered acceptable. But, it can be seen from the graphs reproduced from page 68 on in the review that some of the pairings are more imbalanced than that. Although these imbalances can be produced by a number of means, they can be indicative of the presence of LCN material, so this provides some support for the notion that we are dealing with LCN. Moreover, if you accept that the raw material was “a few hundred picograms” and note that the volume of the solution from which the DNA reading was obtained was 10 microlitres (μl), then it follows that the concentration of that solutions must have been a few tens of pg/μl. According to the review, 200 pg/μl is generally considered to be a threshold below which material should be treated as LCN.

One difficulty with analysing an LCN sample is that, because its presence in a solution is so faint, amplification is required during the PCR process (indeed, it seems clear that Stefanoni did carry out amplification on the sample). Think about this as being like turning up the volume on a cassette player to hear something that has been recorded at a very low volume. Inevitably you are also turning up the hiss. Background noise will normally be easy enough to distinguish from the genuine data, but the real problem is that, as you amplify, you may be amplifying faint traces of contamination that are also present. So, in our case, if there is a reasonable risk that Meredith Kercher’s DNA might have been present as a trace-level contaminant, then the test conducted ought not to be considered reliable.

Conti and Vecchiotti portray this a real risk that could have arisen at any stage of the investigative process, from the recovery of the knife through to the final tests in the lab. They point to a body of scientific literature recommended specific procedures, above what may typically be implemented, in order to minimise the risk of contamination in the recovery, handling and analysis of the evidence, and question whether such procedures were applied in the Kercher case. It is even suggested that the sample from the blade should have been tested in an entirely different laboratory.

I think the strength of this argument varies according to the context you are talking about. Failure to protect against contamination is not necessarily to be excused at any stage. But, from the point-of-view of the results we are considering, it only really matters if there is an appreciable risk that the data observed could have resulted from contamination. So, it should be considered that the location from which the knife was recovered – Sollecito’s flat – is not one where the victim’s DNA would be expected to be present, because it is somewhere where she had never set foot. Regardless of how suitable the procedures carried out there were, there does not seem to be a real risk of contamination.

Similarly, in between the flat and the lab, the knife does not appear to have been in any location where Kercher’s DNA might be supposed to have been present nor handled by anyone who had been in contact with Kercher’s DNA.

As a side note, the review suggests that secondary contamination can never be ruled out in DNA testing, points to an authority that detecting this type of contamination is more likely where LCN is concerned. For example, perhaps Sollecito shook hands with Kercher at some point, then carried her DNA back to his flat and contaminated the knife. In theory, it is probably correct to say that this possibility cannot be ruled out. But the prosecution may be expected to argue that this type of contamination is an ever-present and merely theoretical risk. What the court ought to want to ascertain is exactly how likely such contamination is.

Even if it might be argued that contamination from Kercher’s DNA at Sollecito’s flat or during the initial handling of the evidence is a remote possibility, it is certain that her DNA was present in the lab. At least 50 samples containing it were tested there, 20 or more of them prior to the testing of the knife.

For this reason, a key question for the court is whether the procedures in the lab were adequate for minimising the risk of cross-contamination of samples by the people working there, particularly given the apparent likelihood that the material in question was an LCN sample. The authors of the review don’t categorically say that they weren’t, but that they don’t have enough information to make a judgement. The court at the original Knox/Sollecito trial was satisfied that the standards of the laboratory were adequate in this respect. Will the appeal court take the same view? Will it feel obliged to hold the police scientists to higher standards in light of the review?

If the procedures in place (an actually implemented) in the lab are found to satisfactory, that is not necessarily all there is to it. There are checks on contamination that can be carried out but were not in this case, perhaps in part owing to the small quantity of material being studied.

Ideally, as was conceded by Stefanoni in the original trial, the sample should have been broken into two or more portions to be tested separately. Assuming that similar results would have been replicated on at least two occasions, this would have shown contamination to be less likely.

As a further precaution, the presence of some type of organic material might have been established. Now, it may be felt that the victim’s DNA is the victims DNA. What does it matter whether it came from blood, or skin or whatever? However, if the presence of some particular type of cell were known, then this would provide an indication against the idea that the results were contamination. Stefanoni seems to have performed a test for blood which was negative, and then proceeded on the basis that the sample was too small for the test to have worked properly.

It seems likely that dividing the sample simply wasn’t possible and, although Stefanoni may now wish that she had been more thorough in determining the biological nature of the material she was dealing with, that lapse is probably not enough in itself to invalidate her results.

A bigger problem to my understanding (although the review doesn’t stress it in the way I might have expected) is the issue of how control tests were performed. Standard procedure is to run negative controls, where the test is performed on a saline solution or something else not expected to contain any DNA, so as to check for the presence of contamination already present in the equipment or tube. A positive control should also be run, on a sample whose properties are known, in order to check that the equipment is behaving as it would be expected to (a bit like checking your bathroom scales using a bag of sugar).

These control tests should really be performed not only at the start of testing for each sample, but also when an amplification is performed on a sample. This is particularly important for the negative control, because of the possibility that the amplification will reveal contamination that may not be evident prior to the amplification. But Conti and Vecchiotti report that they see no evidence that this was done. Perhaps the bench will be satisfied if Stefanoni performed the controls without saving them electronically and is able to confirm that no problems were observed. But there’s a clear problem here for the prosecution if it emerges that the controls were not performed.

The most important things for discussion at the next hearing on 25 July will, I think, be the quality of the procedures in place in the police lab for reducing the risk of cross-contamination between samples and the issue of whether or not adequate controls were performed on the knife-blade sample. The reliability of the knife as a piece of evidence in the case really relies on those two things going in the favour of the prosecution.