tag:blogger.com,1999:blog-8731849270338485723.post4436809994939398578..comments2024-01-31T03:00:37.150-05:00Comments on View-from-Wilmington: DNA transfer in StrangulationChris Halkideshttp://www.blogger.com/profile/14933976220776524122noreply@blogger.comBlogger46125tag:blogger.com,1999:blog-8731849270338485723.post-43946221717182841962010-08-22T14:04:00.544-04:002010-08-22T14:04:00.544-04:00To all,
I updated this post after discussing thes...To all,<br /><br />I updated this post after discussing these issues with a forensic nurse. Her comments strengthen the case that swabbing for DNA is justified in cases of attempted strangulation.Chris Halkideshttps://www.blogger.com/profile/14933976220776524122noreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-65751726535238983202010-08-02T06:49:08.092-04:002010-08-02T06:49:08.092-04:00"The problem in discussion was indeed that ac...<i><b>"The problem in discussion was indeed that according to Tagliabracci the DNA on the bra clasp was not enough to have a reliable test. And Stefanoni suggested Comodi to say that instead it was the perfect quantity, being 1.4 nanograms. An ideal quantity. But that revealed a problem: why nobody else knew that measure?"</b></i><br /><br /><a href="http://perugia-shock.blogspot.com/2009/07/day-of-rebellion-for-knox-and-sollecito.html" rel="nofollow">Stefanoni has info the defense did not get</a><br /><br />It makes me wonder what other, possibly exculpatory information she is still holding back.RoseMontaguenoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-45297612528151601572010-07-27T12:43:15.484-04:002010-07-27T12:43:15.484-04:00I think it is very difficult, perhaps impossible, ...<i>I think it is very difficult, perhaps impossible, to predict when a partial profile shows up and when a full profile shows up. The trouble with relying on testimony is that you are relying on someone's memory, which may be faulty. I would rather see laboratory notebooks and various types of files.</i><br /><br />Chris, you and I are both in agreement here. I would definitely like to see laboratory notebooks and various types of files. <br /><br />I would assume that when Stefanoni testified in court she had access to that information via her laptop or notebooks so hopefully she didn't have to rely on memory. <br /><br />ChristianaAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-71880886660195648522010-07-27T09:14:14.492-04:002010-07-27T09:14:14.492-04:00Christiana,
I think it is very difficult, perhaps...Christiana,<br /><br />I think it is very difficult, perhaps impossible, to predict when a partial profile shows up and when a full profile shows up. The trouble with relying on testimony is that you are relying on someone's memory, which may be faulty. I would rather see laboratory notebooks and various types of files.Chris Halkideshttps://www.blogger.com/profile/14933976220776524122noreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-74202479572862701702010-07-24T16:53:36.785-04:002010-07-24T16:53:36.785-04:00Christiana,
I posted a quote regarding this in the...Christiana,<br />I posted a quote regarding this in the next thread regarding the only two female reference samples she had (Amanda and Meredith). You can take that as may be, I have seen this elsewhere just unable to pin it down at present.<br><br />Sefanoni has testified and I think it is clear from her testimony that standards and protocols were not followed for testing LCN DNA. The procedures she followed were completely contrary to protocol and her testimony only confirms this. <br><br />The knife as the murder weapon only works if there is another knife or two involved which has not been proven. The prosecution theory that Amanda carried this around in her bag for protection has not been proven or even shown that it is somewhat likely. The idea that they would get rid of all the other evidence and yet put the knife back in the drawer to use the next time they cooked is a bit whacked. <br><br />As far as the bra clasp goes the video I posted is convincing to me that they "expected" big things from it. That is purely subjective but the way it was left for weeks, moved around somehow, and handled during this video showing the return for this evidence does not inspire me with much confidence in the veracity of the result obtained.RoseMontaguenoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-82137818982954235432010-07-24T13:59:47.858-04:002010-07-24T13:59:47.858-04:00What if one of those partial profiles could be att...<i>What if one of those partial profiles could be attributed to Stefanoni's DNA profile or the DNA profile of one of the Lab Techs? That would certainly be a significant developement. Of course, if you only look for a match with the four reference samples you have (Amanda, Meredith, Rudy, Raffaele) it limits you as to the result. It is either one of theirs or unknown.</i><br /><br />What is known about the partial profiles? Were they degraded profiles (perhaps from being washed with other clothes)? If the partial profiles were from one of the forensic lab technicians would they not be more than partial profiles? And do we know that they were not compared against the profiles of the lab technicians? <br /><br /><i>This is why I think the argument I hear stating that if contamination is not proven then it does not exist is a complete pile of rubbish. My point is you can't find contamination if you don't look for it, so avoiding contamination reports is fairly easy if you overlook the obvious things that may show contamination.</i><br /><br />That is why it would have been important for a representative of the defense to have been at the lab during the testing to see that proper procedures were followed. So we rely on what was testified to in court. I have no reason to believe Stefanoni lied in her testimony concerning procedures that were followed. <br /><br />ChristianaAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-63383889798974143932010-07-23T09:34:27.638-04:002010-07-23T09:34:27.638-04:00What is known of the other three profiles on the b...<b>What is known of the other three profiles on the bra clasp? How partial are they? I believe one has been somewhat attributed to Amanda but even that is in dispute. If it is possible that the profiles are very partial would not the fact that Sollecito's DNA was a full profile be important?<br /><br />Christiana</b><br /><br />What if one of those partial profiles could be attributed to Stefanoni's DNA profile or the DNA profile of one of the Lab Techs? That would certainly be a significant developement. Of course, if you only look for a match with the four reference samples you have (Amanda, Meredith, Rudy, Raffaele) it limits you as to the result. It is either one of theirs or unknown. <br><br />This is why I think the argument I hear stating that if contamination is not proven then it does not exist is a complete pile of rubbish. My point is you can't find contamination if you don't look for it, so avoiding contamination reports is fairly easy if you overlook the obvious things that may show contamination.RoseMontaguenoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-57225298018930134722010-07-22T18:58:32.948-04:002010-07-22T18:58:32.948-04:00Christiana,
The electropherogram that I saw was h...Christiana,<br /><br />The electropherogram that I saw was hard to interpret because the peaks were small. So I do not know how partial or complete they were. I do not think that one can tell much about the how the DNA was deposited by whether the profile is partial or complete. The studies I cited would seem to bear this out. Raffaele's profile is stronger than the partial profiles, IIRC, but it is also weaker than Meredith's; therefore, it is difficult to see why the intensity difference is important in one case but unimportant in another.Chris Halkideshttps://www.blogger.com/profile/14933976220776524122noreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-73758826861971499932010-07-22T18:47:08.561-04:002010-07-22T18:47:08.561-04:00Specifically with respect to the bra clasp, the ex...<i>Specifically with respect to the bra clasp, the exact identities of the other three contributors is important but so is the fact that their DNA is even there. If we accept that their DNA was deposited innocently, how can we be sure that Sollecito’s was not also deposited innocently? The same question should be asked in regards to the mixed profiles found in the sink, as Rose Montague noted above.</i><br /><br />Chris,<br /><br />What is known of the other three profiles on the bra clasp? How partial are they? I believe one has been somewhat attributed to Amanda but even that is in dispute. If it is possible that the profiles are very partial would not the fact that Sollecito's DNA was a full profile be important?<br /><br />ChristianaAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-80183151931763002632010-07-22T18:34:55.312-04:002010-07-22T18:34:55.312-04:00Odeed,
Naturally I am glad to have someone with w...Odeed,<br /><br />Naturally I am glad to have someone with whom to discuss the DNA forensics, even if it is someone with whom I disagree. I welcome different opinions as long as all remains civil.Chris Halkideshttps://www.blogger.com/profile/14933976220776524122noreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-50263450351920748982010-07-22T11:30:59.058-04:002010-07-22T11:30:59.058-04:00Odeed,
With respect to strangulation or restraint...Odeed,<br /><br />With respect to strangulation or restraint, holding someone so tightly that they cannot escape being stabbed with a knife is not the same thing as striking a child, which is the subject of the study in the abstract you cite. <br /><br />With respect to LCN and the kitchen knife, most of the problems originated with the fact that Stefanoni did not know that the sample from the knife had so few copies of DNA. Therefore, she concentrated the sample and dropped the peak threshold from at least 50 RFU to 20 or fewer RFU, to compensate for doing only 28 cycles of PCR, not the typical 34 cycles. It is bad science to change your criterion in the middle of an experiment, and Rrudin and Inman’s “Introduction to Forensic DNA Analysis” (p. 121) specifically cautions, “It is important to have some predetermined limit to distinguish what is signal and what is noise.” In addition, one would have to perform negative controls at the same threshold for the experiment to have any validity, and there is no evidence that Stefanoni did this in the material given to the defense.<br /><br />LCN tests are generally performed twice, and only those alleles showing up in both are scored. There was not enough material for this critical retest. LCN testing is typically done is special facilities equipped with positive air pressure, lighting that destroys DNA and other safeguards against contamination. Such facilities do not appear to have used in this case.<br /><br />For the reasons given above, what Stefanoni did was not standard LCN, and another problem is that her technique has never been judged in a peer-reviewed publication. If she did attempt to publish a paper on this technique, other scientists would be able to critique her work. Thus there is no contradiction between accepting standard LCN while rejecting or criticizing Stefanoni’s homemade version of it. <a href="http://www.sciencespheres.com/2009/10/lcn-dna-profiling-part-ii-watch-where.html" rel="nofollow">Dr. Mark Waterbury</a> does a good job of summarizing these problems.<br /><br />Finally, referring to this ordinary kitchen knife the “double DNA knife” is misleading. DNA cannot be interrogated as to when it was deposited. The presence of Amanda’s DNA on the handle means nothing, because there is an innocent and logical explanation for its being there: she cooked with it.<br /><br />You did not understand why I brought up the Perugia Murder File discussion board. They have a good comment policy, but the site administrators don’t enforce it evenhandedly. I would not tolerate coarse language or rudeness directed toward you and more than I would tolerate it from you. Your attempt to rationalize your earlier sarcastic comments rests on a misinterpretation of what I said in regards to strangulation, as I discussed above. Even in cases where you are (or at least may be) correct, you could learn a thing or two from Rose Montague. When she disagrees, she takes care to do it in a manner that does not demean the other person. Finally, sarcasm is even less justified when a commenter has been wrong. A better course of action would be to concede certain points and move on to others where one has made a better case.Chris Halkideshttps://www.blogger.com/profile/14933976220776524122noreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-60922955089452078122010-07-22T11:28:11.914-04:002010-07-22T11:28:11.914-04:00Odeed,
No, the goalposts have not moved at all, b...Odeed,<br /><br />No, the goalposts have not moved at all, but you may not be putting the pieces together correctly. The prosecution’s theory is what they showed in their animation: Amanda grabbing Meredith by the neck and Rudy and Raffaele later holding her by the arms, as described in the first paragraph of the blog entry. This version of the events indicates that DNA might transfer from the three individuals onto Meredith, as I said in my comment at 6:24 PM on 18 July. There is no getting around the fact that sufficient DNA for forensics might be transferred, especially when one considers the prosecution’s theory of an escalating assault. If DNA can be recovered from certain parts of Meredith’s body, why not other parts?<br /><br />Many of your comments assume that ILE chose not to swab the nape or wrist area because of their knowledge that the profiles might be weak or mixed. In other words, you are assuming that ILE did know of the strangulation studies available at that time, a point that you have previously contested. If they did know, then their pessimism with respect to strangulation and restraint contrasts sharply with their optimism about the knife, when Stefanoni went ahead with the experiment when her DNA quantification test read that it was too low. But a further problem is your implicit assumption that these areas of Meredith’s body were not tested. What if they were tested and came back negative?<br /><br />With respect to the bra clasp you leave out the important fact that Sollecito’s profile was between 5- and 10-fold weaker than Meredith’s. You also ignore the fact that Sollecito’s appeal (approximately on pages 144-145) is questioning whether all of the alleles are his. See the portion of the appeal document beginning with the sentence, “Finally, with regard to the interpretation of DNA profiles extracted from track 165B, the sentence has fallen into a serious and irreparable mistake.”<br /><br />With respect to the analysis of mixtures, you did not comment upon the quotes I provided in a different blog entry. DNA forensic expert <a href="http://www.washingtonmonthly.com/features/2010/1003.bobelian.html" rel="nofollow">Peter Gill</a> said, “If you show 10 colleagues a mixture, you will probably end up with 10 different answers.” With reference to [the Puckett case] case Dan Krane made an important point, “There is a public perception that DNA profiles are black and white. The reality is that easily in half of all cases—namely, those where the samples are mixed or degraded—there is the potential for subjectivity.”<br /><br />Specifically with respect to the bra clasp, the exact identities of the other three contributors is important but so is the fact that their DNA is even there. If we accept that their DNA was deposited innocently, how can we be sure that Sollecito’s was not also deposited innocently? The same question should be asked in regards to the mixed profiles found in the sink, as Rose Montague noted above.<br /><br />To be continued.Chris Halkideshttps://www.blogger.com/profile/14933976220776524122noreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-26956203829600196432010-07-22T07:04:13.475-04:002010-07-22T07:04:13.475-04:00Finally, regarding the posts here and elsewhere, I...Finally, regarding the posts here and elsewhere, I actually joined PMF after posting my first few comments here, and I am aware of others (from either side of the debate) style and substance, but it has not influenced the way I post.<br /><br />In one of my two posts (to date) on PMF forums, I described your blog being authoritative, and yourself as taking a teacher role and the readers as "students" (paraphrase), I should include that I have found your posts to lack any objectivity and on occasion hyperbole when criticizing prosecution.<br /><br />As for my sarcastic reply to Randy, I realised after posting that maybe I should of rephrased it better, but I cannot apologise for it when you make comments such as<br /><br />"The prosecution’s theory predicts that DNA might be deposited in specific locations on Ms. Kercher’s body, and I have suggested that they should have tested their hypothesis."<br /><br />No where has the prosecution made this claim, and this is the first time you have suggested that they did. In your article you correctly summarize the prosecution theory that Kercher was held, and this is because of the nature of the wounds and lack of DNA under her fingernails.<br /><br />This is blatant shifting the goalposts, blaming the prosecution for your theory, and was probably in the back of my mind that you would this when I posted the sarcastic comment.odeednoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-14836719075346814862010-07-22T06:17:02.506-04:002010-07-22T06:17:02.506-04:00In regards to the double DNA knife, I don't th...In regards to the double DNA knife, I don't think I have made any claims to the accuracy/reliability of the profiles found, if anything I am raising the point that you have previously opposed the LCN methods used to test the knife, which does not seem to be any different to the Wiegand 1997 study did in amplifying the DNA profiles.<br /><br />I did not ignore your assertion that in the real world strangulation would leave more DNA than in the studies, you have not proven it. In fact the Wiegand study you cite simulated strangulation on the upper arm so more force could be applied, studies using inanimate objects found low DNA, other studies into assault found little or no DNA http://www3.interscience.wiley.com/journal/120716418/abstract, and the studies methods were to maximise DNA transfer but real world cases have more variables to be concerned with, which is why I am not surprised to see that there is legal cases you can find.odeednoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-35462665552298145632010-07-22T05:04:04.922-04:002010-07-22T05:04:04.922-04:00In regards to the five profile found on the bra cl...In regards to the five profile found on the bra clasp, from what I have read the profiles on consisted of the full DNA profiles of Kercher, and the full profile of Sollecito, and I don't think that the defense disputed that.<br /><br />There were also 3 other profiles, and these remained unidentified, I believe that the defense expert testified that one may have been from Knox, which suggests they were partial profiles.<br /><br />There are plenty of science and legal articles covering interpretation of mixed and partial profiles, and the probabilities involved. Unfortunatley I did not save them for future reference, but one case study I remember was of the Arizona DNA offender database, where 9 loci produced 144 matches in a 65000 person database.odeednoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-34135604781721445142010-07-20T18:18:57.638-04:002010-07-20T18:18:57.638-04:00This New York corrections site
discusses the init...This <a href="http://www.correctionhistory.org/northcountry/html/knowlaw/strangulationinvestigation3.htm" rel="nofollow">New York corrections site </a><br />discusses the initial investigation of strangulation, partly from the point of view of the 911 dispatcher in cases of possible domestic violence. Under the section “medical documentation” it lists “DNA typing of epithelial cells.” It is difficult for me to believe that this refers to obtaining a profile of the alleged victim; therefore, it is more likely to refer to a profile of the alleged assailant. However, greater detail would be helpful, and I will pass it along if I learn something more.Chris Halkideshttps://www.blogger.com/profile/14933976220776524122noreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-57823668676612208142010-07-19T18:24:10.387-04:002010-07-19T18:24:10.387-04:00Odeed,
You are new here, and it is understandable...Odeed,<br /><br />You are new here, and it is understandable that you might assume that this discussion forum is similar to PMF. It is quite different. I ask everyone here to treat each other and their arguments with civility and cordiality. You don’t have to agree with me or anyone else here, but sarcasm indicates disrespect. I have often referred to myself as a student of the Duke lacrosse case; the same term holds for the Cameron Todd Willingham case and the Kercher murder case. In my mind, all of us here are students of this case; no one here is the teacher. Yet as one of the finest scientists I ever met said, “All of us are smarter than any of us.” All of us can learn from one another; no one has the right to use vulgar or belittling language toward anyone else. As long as you act in accordance with these principles, your comments will be welcome here. I don’t ask people to leave because they disagree with me, but I reserve the right to ask that they leave if they are disagreeable.<br /><br />The prosecution’s theory predicts that DNA might be deposited in specific locations on Ms. Kercher’s body, and I have suggested that they should have tested their hypothesis. Your argument boils down to the notion that ILE is not at fault if they did not swab: If they had, they might have generated a partial profile, LCN DNA, or a mixed profile. This position assumes the result before doing the experiment. You ignore the fact that some of the profiles in one study were complete, and you give no reason why a partial profile should be considered an uninterpretable result. Moreover, you continue to ignore the reasons why one might expect more DNA to be transferred in a real-world strangulation than in a simulation. In addition, as Randy correctly pointed out, if you don’t do an experiment, you have no data at all. I would prefer to have some data than no data. <br /><br />You have misunderstood my concerns with respect to the LCN knife profile, many of which are based on the Johnson/Hampikian open letter. One problem with the knife profile is the intensity of the peaks; most are below 50 RFU, and some are as low as about 20 RFU. This is the lowest peak threshold I have ever seen. What would happen if all of the DNA profiles from this case used such a low threshold? A second problem is that LCN is typically performed in dedicated laboratory spaces with features designed to minimize contamination. Stefanoni gave no indication of taking special precautions in her work on the knife. As I have said before, LCN is typically performed twice or even three times to account for alleles dropping in or out. All of these are problems specific to the knife, not general problems of LCN profiling.Chris Halkideshttps://www.blogger.com/profile/14933976220776524122noreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-65100150142984708592010-07-19T08:05:33.976-04:002010-07-19T08:05:33.976-04:00The DNA sample in the sink was also a mixture it a...The DNA sample in the sink was also a mixture it appears: From Amanda's appeal:<br /><br /><br /><i>"4. Finally, we must bring an additional scientific data that contradicts the<br />Grounds.<br />From reading the electropherograms for tracks mixed Knox - since Kercher<br />analyzed here can not exclude the presence of an additional track<br />Biological attributable to third female subject.<br />Dr. Stefanoni said:<br />Ø could not exclude a third person because it profiles<br />very balanced (May 22, 2009 hearing transcript, p.. 222).<br />Ø In that case there may be a third person<br />always female but the same features in<br />this mixture(May 22, 2009 hearing transcript, p.. 229).<br />Ø And she mixed in genetic profiles that relate to the Knox preclude us<br />was a third person? R - This is what I was trying to<br />say. I can not just exclude (hearing transcripts<br />hearing May 22, 2009, p.. 222).<br />Ø These couplings are different so that I can include other<br />people than those already present. This bit is u n 'and the say ...<br />Here of course we talk about compatibility because there are<br />certainly alleles of the victim and Knox, precisely with<br />this combination can not be excluded that there are<br />more ... (transcripts holding a hearing May 22, 2009, p..<br />225).<br />The presence of a third person was also represented by undetectable<br />consultant to plaintiff, Dr. Torricelli.<br />Ø here is a track mixed with the presence surely<br />at least two profiles, there are small peaks that can assume<br />possibly other appearances (June 6, 2009 hearing transcript, p..<br />101).<br /><br />The possibility of a third female person might have<br />lead to Laura Mezzetti and Filomena Romanelli, the other two tenants<br />dwelling.<br />The Scientific Police, however, was not available to the genetic profiles of<br />two other young people.<br />The Stefanoni confirmed at the hearing:<br />Ø D and also had the DNA of other girls who lived in<br />house could also detect the DNA of a third or a fourth<br />girl who lived all saw in the house and used all the<br />same sink? A - If you could see the genetic profiles could<br />compare, that's me in advance I can not say, I can not suppose<br />(Hearing Transcript May 22, 2009, p.. 226)."</i>RoseMontaguenoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-27115337115699254652010-07-18T16:00:35.990-04:002010-07-18T16:00:35.990-04:00Odeed,
If you examine the electropherogram of the...Odeed,<br /><br />If you examine the electropherogram of the knife, you will see that within any given locus, the two alleles differ in peak height by as much as 3-fold, when ideally they should be equal. The inequality of peak height is due to stochastic effects from the low number of DNA templates. Moreover, the peak heights are as small as about 21 RFU. Therefore, the argument that the forensic police did not swab Meredith’s wrist or neck because they did not want to deal with weak samples and/or stochastic effects does not cut much ice with me.<br /><br />I was intrigued by your comment, “and mixed profiles, as you should be aware, is a defense lawyers wet dream, with regards to DNA evidence.” The bra clasp has DNA from several unknown individuals, yet the jury apparently still accepted it as good evidence. Does this not go against your claim?Chris Halkideshttps://www.blogger.com/profile/14933976220776524122noreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-278062974923044942010-07-18T12:23:35.519-04:002010-07-18T12:23:35.519-04:00Christiana,
In situations where the alleged victi...Christiana,<br /><br />In situations where the alleged victim is female and the alleged perpetrator is male, forensic scientists sometimes use <a href="www.promega.com/profiles/801/ProfilesinDNA_801_06.pdf" rel="nofollow">YSTR </a><br /> testing. YSTR testing specifically examines the DNA from the Y chromosome, to circumvent having to look for a small amount of DNA from the alleged perpetrator in a sea of DNA from the alleged victim.<br /><br />Forensic DNA typing has a stronger scientific foundation that most subdisciplines of forensic science. However, there are many complexities that I have only begun to appreciate. It is interesting that about half of all forensic DNA profiles are either a mixture or are a partial profile. Experts do not always come to identical conclusions when analyzing mixtures, as I mentioned in a recent post. The analysis of mixtures is the subject of a number of scholarly articles. A good place to start might be the resources (pdf files and powerpoints) at www.bioforensics.com.<br /><br />My impression is that the amount of DNA to be expected varies with the specifics of crime, among other variables.<br /><br />ChrisChris Halkideshttps://www.blogger.com/profile/14933976220776524122noreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-42252077213099359932010-07-18T08:06:41.096-04:002010-07-18T08:06:41.096-04:00Anyone,
Is it true that mixed profiles are diffic...Anyone,<br /><br />Is it true that mixed profiles are difficult to reference especially if they are of a male/female mixture? <br /><br />It seems I have read (not sure where) that the female DNA masks the male DNA and more sensitive testing needs to be done to extract the male DNA from the mixture (and even that testing is not always successful in extracting a male profile). I do not know how difficult it is to separate mixtures when both are female DNA.<br /><br />I'm beginning to think DNA of a crime scene is much more complicated and fragile than what I previously thought. While it is advantageous to have much DNA from the crime scene to point to a suspect does there exist the possibility you will have very little, even from a particularly brutal crime?<br /><br />ChristianaAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-89307015258480914232010-07-18T06:44:06.592-04:002010-07-18T06:44:06.592-04:00I note the hand waving away of the fact that this ...I note the hand waving away of the fact that this area still be studied. You even include Lowe 2002 which even states in the abstract "...further investigations are underway in order to further add to understanding of the issues of DNA transfer and persistence.", I have no idea how you expect the police to see into the future.<br /><br />@Randy, it is well known that DNA can be obtained from saliva (it's actually common to find saliva around the face and neck area), but it isn't something which Halkides was suggesting, maybe he will in part XX of his classes, along with explanation of how the assailants licked Kercher's wrists to restrain her.odeednoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-52202775721160990862010-07-18T06:11:31.351-04:002010-07-18T06:11:31.351-04:00Lowe 2002 found that full DNA profiles were recove...Lowe 2002 found that full DNA profiles were recoverable one hour after washing, as far as I am aware non of the studies were immediately carried out after washing.<br /><br />Further more, washing hands decreases the chance of mixed DNA profiles, and mixed profiles, as you should be aware, is a defense lawyers wet dream, with regards to DNA evidence.<br /><br />Take Weigand 1997 study, 4 STR loci would be a probability of 1:60000 of an individual match (in the Italian population), Graham/Rutty 2008 found 1-4 alleles of offender DNA which would be a significantly less chance of a match than Weigand.<br /><br />Include the problems LCN and stochastic effects when interpreting mixed profiles, then you have very weak evidence, which is why I am not surprised that you have yet to find any legal cases which would confirm your theory.odeednoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-28123336755690786282010-07-18T05:16:55.756-04:002010-07-18T05:16:55.756-04:00halides1,
Van Oorschot 1997 found that the DNA re...halides1,<br /><br />Van Oorschot 1997 found that the DNA recovered from surfaces touched was relatively high (upto 150 ng) and profiles were recovered using standard STR, Ladd 1999 repeated the study with the similar techniques but discovered that the DNA was low (upto 15ng) and that the profiles recovered were close to background noise and therefore uninterpretable.odeednoreply@blogger.comtag:blogger.com,1999:blog-8731849270338485723.post-25027418996828667892010-07-17T14:10:29.592-04:002010-07-17T14:10:29.592-04:00Odeed,
Let’s examine handwashing and its effect o...Odeed,<br /><br />Let’s examine handwashing and its effect on completeness of recovery. Figure 1 in the 2002 study by Lowe et al. shows that the percentage of a full profile of DNA rises over the course of minutes to hours after handwashing. Good shedders show the most differentiation from poor shedders at 15 minutes. Therefore if a study of DNA deposition incorporates a handwashing step a few minutes before the DNA is deposited, it will probably result in less complete profiles than if no handwashing were done. This observation, coupled with the fact that the studies cannot match the combination of time and pressure of an actual strangulation, contradict your claim that “the lab methods chosen were to increase the probability of offender/victim transfer.”<br /><br />The 1997 paper by Wiegand and Kleiber only looked at the CD4, FGA, TH01, and VWA loci. The relatively long period of time, 48 hours, between the strangulation and the finding of the body, might have decreased recovery in this actual case study. The 2002 study by Rutty used either 28 cycles of amplification or 34 cycles. The 2008 study by Graham and Rutty used 28 cycles, except when assessing shedder status.<br /><br />With respect to LCN, I have some reservations with respect to the standard LCN technique. However, my main issues with LCN in the Knox/Sollecito case is that the knife profile was generated with an inferior version of LCN. Dr. Tagliabracci’s argument to the effect that Raffaele’s profile on the clasp was below at least one threshold for LCN raises the question of why it was not run at least twice, as is typical for LCN forensic typing.Chris Halkideshttps://www.blogger.com/profile/14933976220776524122noreply@blogger.com