How would they explain the gap?
Amanda Knox guilty - all because of a cartwheel
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How would they explain the gap?
Fulcanelli
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Also, because the police seized the diaries from all of the accused as evidence, so the public could hardly be lied to about what was in them as the ILE would be able to expose the lie at any point
Also, it must be noted, the original intent of Sollecito's lawyers was to submit his diary in his defence (clearly at a later time they changed their minds about doing so), as they believed they showed him to be innocent. Submitting doctored (edited) evidence would have been a crime.
stilicho
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I was mainly wondering what halides1 knows that Tagliabacci doesn't know. If they both know the same things then that battle was fought and lost in SEP 2009. If halides1 has some exciting new evidence that the defence teams don't have then it might be a good idea to explain how they differ.
We cannot know this until halides1 tells us.
Since they were in prison while the case dragged on I guess it was their time to waste. It seems bizarre though that they couldn't come up with a defence team who weren't too busy with other commitments to attend court. Is that why they didn't go and observe the DNA analysis as well? If I'm ever in that unfortunate position, I'll hire a lawyer who's only able to attend court on February 29th - I'll claim all the other days are his people's sabbath or something.
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Chris_Halkides
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Thompson
Stilicho,
From Professor William C. Thompson comes an example of cross contamination with relevance here:
“In one particularly interesting Australian case, DNA on the clothing of a murdered toddler named Jaidyn Leskie was linked, via a ‘cold hit,’ to a young ‘mentally challenged’ woman who lived hundreds of miles away and who, by all accounts, had never left her own village. Police could find no way to link the young woman to the Leskie murder and at first dismissed the ‘cold hit’ as an ‘adventitious’ (coincidental) match. However, a coroner’s investigation established that DNA from the young woman had been processed through the same laboratory at about the same time as the toddler’s clothing. The young woman had allegedly been the victim of a sexual assault involving a condom. Although laboratory personnel maintain that accidental transfer of samples between cases is impossible, it now appears almost certain that the young woman’s DNA from the outside of the condom accidentally contaminated samples from the toddler’s clothing.”
http://www.nacdl.org/public.nsf/0/6285f6867724e1e685257124006f9177
One can argue that the mentally challenged woman did indeed murder the toddler, but it seems at least equally probable that this was a case of cross contamination, despite the presumably good-faith protestations of the laboratory personnel. Professor Thompson gives a second example as well. One must bear in mind that about 1/1,000,000 of a sample of post-PCR DNA is enough to contaminate a pre-PCR sample.
Stilicho,
From Professor William C. Thompson comes an example of cross contamination with relevance here:
“In one particularly interesting Australian case, DNA on the clothing of a murdered toddler named Jaidyn Leskie was linked, via a ‘cold hit,’ to a young ‘mentally challenged’ woman who lived hundreds of miles away and who, by all accounts, had never left her own village. Police could find no way to link the young woman to the Leskie murder and at first dismissed the ‘cold hit’ as an ‘adventitious’ (coincidental) match. However, a coroner’s investigation established that DNA from the young woman had been processed through the same laboratory at about the same time as the toddler’s clothing. The young woman had allegedly been the victim of a sexual assault involving a condom. Although laboratory personnel maintain that accidental transfer of samples between cases is impossible, it now appears almost certain that the young woman’s DNA from the outside of the condom accidentally contaminated samples from the toddler’s clothing.”
http://www.nacdl.org/public.nsf/0/6285f6867724e1e685257124006f9177
One can argue that the mentally challenged woman did indeed murder the toddler, but it seems at least equally probable that this was a case of cross contamination, despite the presumably good-faith protestations of the laboratory personnel. Professor Thompson gives a second example as well. One must bear in mind that about 1/1,000,000 of a sample of post-PCR DNA is enough to contaminate a pre-PCR sample.
Fulcanelli
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halides1 said:
'It seems'...'maybe'...'probable'. And what does it have to do with 'this' case again? At most, all your case study suggests is that contamination is 'possible'. Didn't we all know that already?
The basis of your argument seems to be that contamination is possible. Because contamination is possible, we must therefore reject all DNA evidence against the pair.
The flaw of course, is that the 'contamination is possible' argument can apply equally to every single case in history where DNA has formed part of the evidence. The one exception in the history of humankind, it would seem, is Rudy Guede. Do I have it about right?
halides1,
Surely the key thing here is that he calls it a cold hit? He is talking about the odds of some random bit of DNA floating around in the lab contaminating the sample. This isn't at all the same as it being the DNA of somebody already involved in the case floating around around the lab and happening to contaminate the sample and none of the controls. The odds of that are, I hope you'll agree, very much lower.
Do you have any quotes that relate to the kind of scenario we are talking about rather than a hit against a DNA database?
Surely the key thing here is that he calls it a cold hit? He is talking about the odds of some random bit of DNA floating around in the lab contaminating the sample. This isn't at all the same as it being the DNA of somebody already involved in the case floating around around the lab and happening to contaminate the sample and none of the controls. The odds of that are, I hope you'll agree, very much lower.
Do you have any quotes that relate to the kind of scenario we are talking about rather than a hit against a DNA database?
You are again questioning the DNA on a hypothetical contamination basis. Where is your proof? Could be is not an argument, it's a hypothesis which needs to be backed.
Has the professionalism and diligence of the lab that did the analysis ever been called into question? And if so, why did the defense with its greater access to case information only speculate about possible contamination?
Carefully examine your own mind, do you believe it to be possible that the DNA analysis is evidence for Amanda Knox killing Meredith Kercher?
Has the professionalism and diligence of the lab that did the analysis ever been called into question? And if so, why did the defense with its greater access to case information only speculate about possible contamination?
Carefully examine your own mind, do you believe it to be possible that the DNA analysis is evidence for Amanda Knox killing Meredith Kercher?
Chris_Halkides
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not a cold hit
shuttit,
May I gently suggest that you have misunderstood what I meant? Both of the examples Thompson delineates were thought to be cold hits, but were more likely caused by contamination. Given the number of times Meredith's DNA must have been amplified, between evidence samples and reference samples, her DNA is among the most likely possible contaminants in the lab. Also, the references I gave indicate that contamination may or may not be an across-the-board phenomenon.
Chris
shuttit,
May I gently suggest that you have misunderstood what I meant? Both of the examples Thompson delineates were thought to be cold hits, but were more likely caused by contamination. Given the number of times Meredith's DNA must have been amplified, between evidence samples and reference samples, her DNA is among the most likely possible contaminants in the lab. Also, the references I gave indicate that contamination may or may not be an across-the-board phenomenon.
Chris
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Chris_Halkides
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On a knife's edge
To all,
Fiona wrote, “The generalisations from ‘experts’ who did not see all the evidence, and who have vested interests of various kinds, are not persuasive in this context.” If this is meant to refer to the signers of the open letter, it is clearly false; they included the electropherogram in their letter. Let’s examine this first.
There are four basic problems with the profile of DNA culled from the knife. The first is the weakness of the signals. The signals one typically observes are in the many hundreds or thousands of RFUs. Dr. Tagliabracci noted in a document linked and discussed here that the lower limit of detection is not less than 50 RFU. The document is in Italian and is available as a pdf file. In Darkness Descending, one of Italy’s top forensic scientists, General Luciano Garofano, noted that 100/150 RFU is usually considered to be the minimum. There are arguments in the literature about setting this threshold differently. Fine; this is an area of dispute, but consistency within the lab is equally critical, as discussed below.
Indeed, a second, more serious issue is that one should always set the threshold before doing the experiment. This limit was 50 RFU. Stefanoni herself wrote on a knife-related document, “too low.” Changing the limit after the experiment was done opens the door to bias. Here is where the warning from Rudin and Inman (message #2525) becomes pertinent. It is entirely appropriate and praiseworthy for textbooks to discuss good scientific ethics, the principles of which do not change with the seasons.
The third problem with this DNA profile is the appearance of two peaks in locus D3S1358, both of which have a signal-to-noise ratio of about twenty, and neither of which is part of Meredith’s profile. The fourth problem with this profile is that eight loci, D7S820, D16S539, D19S433, vWA, TPOX, D18S51, D5S818, FGA, have pairs of peaks in which the smaller peak is less than 70% of the height of the larger one. This value is typically 70-100% in a single source sample (Butler, Forensic DNA Typing, pp. 155-156). The problems noted above all support taking a conservative interpretation of the profile, as the signers of the open letter did. They refer to it as a “partial profile.”
If the profile is Meredith’s, the question is how did it arise. My comment #2519 quoted Dr. Johnson, who indicated that the DNA would be removed from the knife more quickly than the blood. Therefore, the lack of blood makes it impossible for there to be DNA on the knife, and the DNA that was observed has to arise from contamination from mechanisms similar to those documented by Professor Thompson (comment #2585). However, one might argue that it is only improbable that some DNA would remain on the knife. If one could support this latter interpretation, then one would be left with choosing between two events, contamination or DNA somehow escaping removal. General Garofalo wrote, “"Did they open the knife to see if blood had dripped between the metal part of the handle and the plastic? No? Pity. That would have been a sure place to find blood if there was blood. Secondly, they say it was cleaned with bleach. If an object is cleaned with bleach, there is no DNA left. And if any were left there would be the same amount of DNA belonging to Amanda Knox as to Meredith Kercher. Next to nothing…So the fact that there is a lot of Amanda Knox's DNA and a little of Meredith's doesn't sound logical to me.”
Dr. Donald Riley wrote (http://www.scientific.org/tutorials/articles/riley/riley.html):
(1) A partial profile essentially proves that one is operating outside of well-characterized and recommended limits.
(2) Contaminating DNA usually presents as a partial profile, although not always. For this reason, the risk that the result is a contaminant is greater than for samples that present as full profiles.
(3) A partial profile is at risk of being incomplete and misleading. The partial nature of it proves that DNA molecules have been missed. There is no way of firmly determining what the complete profile would have been, except by seeking other samples that may present a full profile.
Recall that we are dealing with a partial profile in this instance.
Recently, I was fortunate enough to discuss this case with a graduate of our department who is now a forensic scientist in a municipal police department. When I told her about the knife, she asked whether or not they had checked other knives from the drawer for DNA. That’s a good example of thinking like a scientist: This unperformed experiment would have shed light on whether or not contamination had occurred. The prosecution has not released the fsa files, an almost unheard of occurrence in DNA forensics. The open letter of 19 November 2009 noted their absence, despite comments here to the contrary, which only indirectly address the issue of their release. Analysis of these files might also shed light on possible contamination. To sum up, the failure to perform the analysis on other knives and the lack of independent review reduce the value of this DNA profile.
The authors of the open letter wrote, “There exists the real possibility that the low level, partial profile attributed to the knife blade is a result of unintended transfer in the laboratory during sample handling… No credible scientific evidence has been presented to associate this kitchen knife with the murder of Meredith Kercher.” That is more than sufficient to create reasonable doubt about the knife’s being involved in the murder, in addition to the other problems associated with this knife.
And to all a good night.
Chris
To all,
Fiona wrote, “The generalisations from ‘experts’ who did not see all the evidence, and who have vested interests of various kinds, are not persuasive in this context.” If this is meant to refer to the signers of the open letter, it is clearly false; they included the electropherogram in their letter. Let’s examine this first.
There are four basic problems with the profile of DNA culled from the knife. The first is the weakness of the signals. The signals one typically observes are in the many hundreds or thousands of RFUs. Dr. Tagliabracci noted in a document linked and discussed here that the lower limit of detection is not less than 50 RFU. The document is in Italian and is available as a pdf file. In Darkness Descending, one of Italy’s top forensic scientists, General Luciano Garofano, noted that 100/150 RFU is usually considered to be the minimum. There are arguments in the literature about setting this threshold differently. Fine; this is an area of dispute, but consistency within the lab is equally critical, as discussed below.
Indeed, a second, more serious issue is that one should always set the threshold before doing the experiment. This limit was 50 RFU. Stefanoni herself wrote on a knife-related document, “too low.” Changing the limit after the experiment was done opens the door to bias. Here is where the warning from Rudin and Inman (message #2525) becomes pertinent. It is entirely appropriate and praiseworthy for textbooks to discuss good scientific ethics, the principles of which do not change with the seasons.
The third problem with this DNA profile is the appearance of two peaks in locus D3S1358, both of which have a signal-to-noise ratio of about twenty, and neither of which is part of Meredith’s profile. The fourth problem with this profile is that eight loci, D7S820, D16S539, D19S433, vWA, TPOX, D18S51, D5S818, FGA, have pairs of peaks in which the smaller peak is less than 70% of the height of the larger one. This value is typically 70-100% in a single source sample (Butler, Forensic DNA Typing, pp. 155-156). The problems noted above all support taking a conservative interpretation of the profile, as the signers of the open letter did. They refer to it as a “partial profile.”
If the profile is Meredith’s, the question is how did it arise. My comment #2519 quoted Dr. Johnson, who indicated that the DNA would be removed from the knife more quickly than the blood. Therefore, the lack of blood makes it impossible for there to be DNA on the knife, and the DNA that was observed has to arise from contamination from mechanisms similar to those documented by Professor Thompson (comment #2585). However, one might argue that it is only improbable that some DNA would remain on the knife. If one could support this latter interpretation, then one would be left with choosing between two events, contamination or DNA somehow escaping removal. General Garofalo wrote, “"Did they open the knife to see if blood had dripped between the metal part of the handle and the plastic? No? Pity. That would have been a sure place to find blood if there was blood. Secondly, they say it was cleaned with bleach. If an object is cleaned with bleach, there is no DNA left. And if any were left there would be the same amount of DNA belonging to Amanda Knox as to Meredith Kercher. Next to nothing…So the fact that there is a lot of Amanda Knox's DNA and a little of Meredith's doesn't sound logical to me.”
Dr. Donald Riley wrote (http://www.scientific.org/tutorials/articles/riley/riley.html):
(1) A partial profile essentially proves that one is operating outside of well-characterized and recommended limits.
(2) Contaminating DNA usually presents as a partial profile, although not always. For this reason, the risk that the result is a contaminant is greater than for samples that present as full profiles.
(3) A partial profile is at risk of being incomplete and misleading. The partial nature of it proves that DNA molecules have been missed. There is no way of firmly determining what the complete profile would have been, except by seeking other samples that may present a full profile.
Recall that we are dealing with a partial profile in this instance.
Recently, I was fortunate enough to discuss this case with a graduate of our department who is now a forensic scientist in a municipal police department. When I told her about the knife, she asked whether or not they had checked other knives from the drawer for DNA. That’s a good example of thinking like a scientist: This unperformed experiment would have shed light on whether or not contamination had occurred. The prosecution has not released the fsa files, an almost unheard of occurrence in DNA forensics. The open letter of 19 November 2009 noted their absence, despite comments here to the contrary, which only indirectly address the issue of their release. Analysis of these files might also shed light on possible contamination. To sum up, the failure to perform the analysis on other knives and the lack of independent review reduce the value of this DNA profile.
The authors of the open letter wrote, “There exists the real possibility that the low level, partial profile attributed to the knife blade is a result of unintended transfer in the laboratory during sample handling… No credible scientific evidence has been presented to associate this kitchen knife with the murder of Meredith Kercher.” That is more than sufficient to create reasonable doubt about the knife’s being involved in the murder, in addition to the other problems associated with this knife.
And to all a good night.
Chris
Thankyou for the delicate way you put that halides1, I will rephrase.
How many different DNA profiles will be foating around that lab potentially contaminating things? It is certainly considerably less than will be contained within a DNA database, but it is still a lot. In the case of your examples a random DNA sample in the lab caused the contamination. In this case it was a sample relating to the case. The odds of this are very much lower.
In any case, if this kind of cross contamination is going on with any appreciable frequency it will be showing up as spoiled negative controls, incidents like the one you posted and failed audits. Presumably the defence will have investigated to see whether any of these things have happened? I take it the lab do log these kind of events in a way that would allow some kind of judgement to be made about the likelihood of contamination? The negative controls alone reduce the odds that it happened quite a bit.
I've become curious about how much time was actually spent in court on this trial; not that it's important, but it's hard to pin down.
We know that it began on January 16th and ended on December 5th. The Guardian says: "Trials in Italy proceed at a leisurely pace of, at most, two hearings a week and this one took eight months." I'm not sure where they get 8 months.
I also found this page, which contains an ABC news clip from September 14th, marking the resumption of proceedings after a two-month summer recess. Putting this all together and assuming two trial days per week apart from that summer recess, we get 78 days in court, stretched over 11 months.
Fulcanelli
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How come nobody 'else's' DNA got amplified? You see the catch 22? If you're going to argue that amplification beyond normal sensitivity amplified Meredith's DNA that was there purely as the result of contamination, you then have to explain that if that's the case, how it that it was contaminated with nobody else's DNA? How is that possible? And more importantly, is it even remotely probable? You not only have to explain how 'contamination' in general was probable, but also how that contamination happened to be Meredith's and also even more importantly, how nobody else's DNA was on there.
In a busy lab, if there'd been some failure in either the handling of the chain of evidence, or in lab protocols, we'd expact to see that knife contaminated with the DNA of every man and and his dog. At the very least, of several people. Yet, there was the DNA of only one, Meredith. What are the odds of that bullseye???
This is a point of plain basic logic. Scientists should be able to appreciate it.
Now, can we get back to the 'real' World please?!
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Sorry, Chris, this has been mentioned before and I still don't understand where the contaminant is supposed to be coming from on the other knives that would warrant this? Are you speculating that somebody has been in contact with the knives whose profile is sufficiently close to Merediths to provide the false match? Are you suggesting that members of the search team from Merediths appartment contaminated the team that searched Raffaele's apparment who then contaminated the knives?halides1 said:
I've asked before without being answered. Is it normal in the US/UK, or wherever else we can agree lives up to an acceptable standard in such matters, for the police to send audit/control items for analysis during cases like this? I genuinely don't know the answer to my question. If they do it's news to me, if not it seems to me that it weakens your point somewhat.
If the theory is that the knife/knives were sitting in the draw with this DNA on them then its a pity that the defence didn't take it upon themselves to have the other knives analysed. Perhaps they weren't allowed? or too much time had passed by the time they thought of it? Or like witnessing the DNA test, they didn't see the point?
You know, if the defence believed Raffaele's story about Meredith cutting herself on the knife, they should surely have hot footed it around to his appartment and swabbed things he thought she might also have touched/bled on. If the DNA on the knife survived, it might have survived elsewhere as well? A bit of DNA or even better, a fingerprint proving that she'd been there would help his case a lot. Maybe they don't have budget to do those kind of things? Or were they not allowed? I mean, if she'd cooked dinner there only a week earlier there is some hope of finding something isn't there?
There seems to be a theme here:
On the one hand we have the claim that it was negligent and deceitful of the italian police not to record the interviews when the defendents were only witnesses, on the other hand I'm told that in the UK it isn't procedure to record interviews with witnesses either (and I've heard nothing about what the rule book says in the US).
On the one hand the claim is that the proper thing to do would have been to send negative control cutlery from the draw to the lab for analysis, on the other hand I've certainly never heard of this being a standard thing to do and nobody seems to be forthcoming with evidence that it is.
On the one hand we have the claim that it was negligent and deceitful of the italian police not to record the interviews when the defendents were only witnesses, on the other hand I'm told that in the UK it isn't procedure to record interviews with witnesses either (and I've heard nothing about what the rule book says in the US).
On the one hand the claim is that the proper thing to do would have been to send negative control cutlery from the draw to the lab for analysis, on the other hand I've certainly never heard of this being a standard thing to do and nobody seems to be forthcoming with evidence that it is.
Dan O.
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You should read the thread and not just the last post. It's already been show that cross contamination in the labs occurs and that this can result in a match to a single profile.
Fulcanelli
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You should read the thread and not just the last post. It's already been show that cross contamination in the labs occurs and that this can result in a match to a single profile.
They weren't investigating the woman in the first place. If you get a random profile up and match it to a database of thousands or even millions of people, it's likely to match 'someone'. The more people that are being compared to, the higher the odds that someone is going to fit the profile. The DNA on the blade didn't pull someone out of a hat containing thousands or millions of profiles, it came up for Meredith Kercher, the girl that happened to be the murder victim and had prompted the whole requirement to examine the knife in the first place. Now...what are those odds?
And I wouldn't mind here, but halides1's case study is laced with words like 'maybe' and 'probably'. It hasn't even been established that it was indeed contamination and for all we know, the woman may have been the murderer.
You're comparing apples and oranges.
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Chris_Halkides
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detecting contamination
Shuttit,
Undoubtedly, most of the knives in the drawer would have been free of Meredith’s DNA (even if one were the murder weapon, not all of them could have been). Therefore, if several knives had shown DNA profiles from Meredith (or anyone other than Raffaele and Amanda, I suppose), one could be certain that contamination had occurred. To wit: If my hypothesis is that the chef’s knife is the murder weapon, then if Meredith’s DNA shows up on the steak knife, my hypothesis was falsified. The reason I did not answer your question earlier is that I am more at home discussing scientific methods than I am discussing what standard forensic practice is. Historically, the two have not always been the same.
If Meredith’s DNA had shown up on multiple knives, the contamination might come from handling the knife after handling one of Meredith’s possessions without changing gloves. However, it is also possible that contamination would have occurred in the lab. As I have noted before, the introduction of PCR into DNA typing has increased the possibility of contamination. I have also noted before that when contamination occurs, it is seldom possible to identify how it happened. A good analogy is that one can seldom pinpoint when one acquired the virus that produced a common cold; one just knows it had to happen somehow from one’s runny nose.
Chris
Shuttit,
Undoubtedly, most of the knives in the drawer would have been free of Meredith’s DNA (even if one were the murder weapon, not all of them could have been). Therefore, if several knives had shown DNA profiles from Meredith (or anyone other than Raffaele and Amanda, I suppose), one could be certain that contamination had occurred. To wit: If my hypothesis is that the chef’s knife is the murder weapon, then if Meredith’s DNA shows up on the steak knife, my hypothesis was falsified. The reason I did not answer your question earlier is that I am more at home discussing scientific methods than I am discussing what standard forensic practice is. Historically, the two have not always been the same.
If Meredith’s DNA had shown up on multiple knives, the contamination might come from handling the knife after handling one of Meredith’s possessions without changing gloves. However, it is also possible that contamination would have occurred in the lab. As I have noted before, the introduction of PCR into DNA typing has increased the possibility of contamination. I have also noted before that when contamination occurs, it is seldom possible to identify how it happened. A good analogy is that one can seldom pinpoint when one acquired the virus that produced a common cold; one just knows it had to happen somehow from one’s runny nose.
Chris
Fulcanelli
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How's it possible it was contaminated by Meredith's DNA, someone who didn't live there, yet not even Raffaele's or Amanda's (who did) or the maid's who cleaned there, or that of the police officer who retrieved it was on that blade?
Too far fetched. You need to give it up.
Dan O.
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Has it actually been proven that Meredith never visited Raffaele's apartment? Do we have a diary of every place Meredith visited while in Perugia?
But that aside, the most probable source of contamination is the amplified DNA from the 200+ samples collected at the cottage and analyzed in the same lab. The video we've seen shows a lab technician using a pair of metal tweezers to to collect the sample from the knife on a blotter. These were not disposable tweezers as required practice when doing LCN DNA testing. These were ordinary reusable lab tweezers. There is no tracking in the lab to follow how the tweezers were used in the previous weeks. They were probably washed between uses. But if washing were sufficient, there would be no DNA on the knife either.
So there it is. The DNA from meredith could have come from the knife -or- the DNA that was in the lab could have been transfered on the tweezers.
With these two options and no measurements of the contamination levels in the lab and no repeatability of the test, we are left with at best a 50/50 probability for each.
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