Tuesday, July 20, 2010

To those who believe that Amanda Knox and Raffaele Sollecito are guilty, I issue a challenge.

Part 20 in the Knox/Sollecito case

Francesco Maresco, lawyer for the Kercher family, said after the verdict last December, “We are teaching the whole world and the United States how to collect, analyse and evaluate scientific technical aspects of the case.”

I have previously discussed how the electronic data files are used by independent experts in criminal cases. Those arguments are especially compelling in the murder of Meredith Kercher, in which the amount of DNA in two of the most important pieces of DNA evidence fall near or into the low copy number (LCN) range. The profile from the bra clasp is also a mixture, and it is well known that the analysis of mixtures introduces subjectivity into the analysis. I have also previously given my reasons for believing that these critical files were never released to the defense teams. Since that time some additional information has become available that puts this question to rest.

Raffaele Sollecito’s appeal documents indicate that his defense expert Dr. Pascali requested the raw data in 2008 (presumably the electronic data files). This request was prior to the preliminary hearing, and the lawyers supported their request with a reference to article 415. They also requested the log files. The judge granted the defense teams the right to forensic information in the summer of 2009 that they had been denied until that time. However, the prosecutions did not fully comply with this order, according to a source close to the defense, and this was one of the things that precipitated the defense teams’ asking for a mistrial in September of 2009.

An open letter coauthored by Dr. Elizabeth Johnson and Professor Gregory Hampikian noted that the prosecution failed to release the electronic data files (.fsa files) to the defense. Since the time of the letter’s release on 11/19/09, some have assumed that these two DNA forensic scientists were unrelated to the case and therefore had no standing to ask for these files. This argument is false. An article written by Fiona Ness on 25 April 2010 indicates that Professor Hampikian is a consultant for Amanda Knox’s defense team. As such, he has every reason to request the operating procedures of the lab, as well as the electronic data files that produce the electropherograms.

“The importance of DNA evidence in a conviction is highlighted in one of Hampikian’s cases - that of US student Amanda Knox. Knox was convicted of the murder of British student Meredith Kercher after a high-profile trial in Italy in 2009. Knox’s conviction was partly based on a sample of her DNA discovered on a knife found in the house. However, Hampikian says he is appalled by the standard of DNA evidence used by the Italian courts to convict Knox in the case. ‘The amount of DNA present is far below the normal cut-off for many labs that I know of. A one off spurious piece of DNA evidence shouldn’t be treated as a gold standard profile from a high-profile source. The issue of this low-template DNA sample is really troubling me.’ Trying to obtain the evidence to have it retested, however, is proving difficult. ‘The discovery rules in Italy are different to what I’m used to. It’s fairly routine in the US that I send a request and get what I want. But in the Knox case I haven’t been able to get a copy of the standard operating procedures of the lab and without that, it’s hard to see if they even followed their own guidelines.’ Evidence, Hampikian says, is a matter of science, to be reviewed, not protected.” (emphasis added) An article in the Irish Times confirms that a professional relationship exists between Professor Hampikian and the Knox family.

The words of an anonymous forensic DNA expert unconnected with the murder of Meredith Kercher are apropos here. This individual said with reference to a different case, “Honest differences of opinion by qualified experts should be welcomed by the Court. This can only be accomplished if the independent expert is provided full and complete discovery by the government.” Keith Inman and Norah Rudin gave ten ways to improve forensic science. Number five was “Provide transparency. Secrecy and gamesmanship are inappropriate to the work of the forensic scientist. All laboratory notes, data, results, procedures, logs, and records should be open to controlled
and appropriate scrutiny.”

To those who believe Ms. Knox and Mr. Sollecito are guilty, I respectfully issue a challenge: Join me in calling for the release of all of the forensic information that the defense has been denied until now. Some among you have argued that the Italian authorities should not release any more information than that demanded by Italian law. However, it is conceivable that Italian law is not yet settled on the question of whether or not to release the electronic data files. If it is not, why should the precedent be against full disclosure rather than in support of full disclosure? If the case against the defendants is as strong as you say it is, you have nothing to fear. On the contrary, your certainty would be stronger if the release and examination of these files produced nothing.

To the Italian authorities I respectfully issue a related challenge: Make good on Mr. Maresca’s claim. Show the world that forensic evidence is to be shared with the defense. At that point the analysis will be complete. Provide the electronic data files (.fsa files), and the instrument log files, and include the contamination log files if they exist. Then and only then will you indeed be showing the world the right way to treat forensic evidence.

Tuesday, July 13, 2010

DNA transfer in Strangulation

Part XIX in the Knox/Sollecito case

Update 1, 22 August 2010

I communicated with an anonymous forensic nurse about their domestic violence program. If an alleged victim complained of an attempted strangulation, complained of a partner’s grabbing their arm, or showed bruising or redness, they have been swabbing that area for DNA, for two years. Positive results in at least one case helped to convict someone. This information confirms the reasonableness of swabbing Meredith’s body in appropriate places, although the bruise on the nape of Meredith’s neck may have been the result of her being thrown against the wall (as some have theorized). We do not know whether swabbing the bruised areas was done or not.

PM Guiliano Mignini’s reconstruction of the murder of Meredith Kercher was shown to the jury in the form of an animated video. In his speculation Amanda Knox grabbed Meredith Kercher by the throat and slammed her against a wall. The video superimposed actual shots of Meredith’s bruises with Amanda’s animated hand to imply that Amanda’s action produced the bruises. Later, Rudy Guede and Raffaele Sollecito held Meredith’s arms back, and Amanda stabs her (Barbie Nadeau, Angel Face, p. 160). In forensics professor Carlo Torre’s reconstruction of the crime, the single assailant grabbed Meredith by the throat and stabbed her. The area under Meredith’s chin and her nape were bruised; the former bruising was the result of the knife and the latter when the assailant put Meredith down.

Although Mignini’s theory of the crime suggests a much longer amount of contact between the assailants and victim than does Torre’s, both imply contact. None of Amanda Knox’s DNA was found in Meredith’s bedroom or on her body. Raffaele Sollecito’s DNA was found on a bra clasp (although the defense contests this piece of evidence) but not the bra itself. Rudy Guede’s DNA was found in several places, including on the sleeve of Meredith’s sweatshirt. Let us examine some forensic DNA studies to see if they shed any light on this tragedy.

The study by Wiegand and Kleiber gives a case study in which DNA evidence was collected 48 hours after a strangulation. They wrote, “Strangulation marks were clearly visible on the neck of the victim. Epithelial cells could be removed from the neck of the victim using separate cotton swabs for the left and the right side of the neck. Only the swab from the right side could be typed and included the pattern of the suspect (Fig. 3), a result which corresponded to the autopsy findings (the right neck side showed a higher intensity of bleeding in the muscles than the left side indicating a more intensive pressure against the right side). Altogether clear results could be obtained using four STRs (TH01, VWA, FGA, CD4) demonstrating the high utility and sensitivity of the method described.” These authors also conducted simulated strangulations, and they reported a success rate of better than 70%.

The simulated strangulation study in 2002 by Rutty used both SGMplus and LCN amplification. The simulated strangulation experiment was done with periods between the force and the sampling were 1, 5, 10, 15, 30, and 60 min, 2, 3, 4, 5, 6, 7, 8, 24, and 48 h and 3, 4, 5 and 10 days. When the author used SGMplus, he observed a full profile of the offender 7 out of 29 times, and always in the presence of the victim’s profile. When the author used LCN all 17 experiments yielded offender profiles, with the majority being partial profiles. Dr. Rutty wrote, “Of the test neck swabs, 19 yielded positive amplification results using SGMplus, 12 showed a victim-only profile and 7 a victim and offender profile with a full offender profile detectable up to 6 h after contact. When LCN was used (17 tests) all showed the offender to be present for all time periods i.e. up to 10 days. In the majority of cases it was a partial offender profile with the majority of the amplification result being a full victim profile.”

Dr. Rutty stated that “When considering the apparent time periods of DNA survival, passive transfer of the offender’s DNA onto the victim’s neck could also explain the presence of offender DNA several days after contact.” This study did not break down the results by time periods between simulated strangulation and DNA collection; therefore, it is difficult to draw firm conclusions based solely on the data presented.

A 2008 study by Graham and Rutty reexamined the question of DNA transfer to and from strangulation victims with an emphasis on innocent DNA transfers that might deposit DNA on the neck of a victim. In 24% of samples collected showed nonself DNA on the simulated victim from third party sources. The authors believe that such DNA transfers might confuse an investigation.

Finally, it might be helpful to return to the subject of primary and secondary DNA deposition. The study by Lowe and coworkers in 2002 looked at DNA transfer from a good DNA shedder to a poor DNA shedder to an object. By definition transfer was secondary from the good shedder, and transfer was primary from the poor shedder. When mixtures were observed, secondary transfer from the good shedder provided the major component, not primary transfer from the poor shedder. This study illustrates the dictum that one generally cannot infer the mechanism of how the DNA was deposited from the DNA itself. Along with the study by Graham and Rutty, this work suggests caution in the interpretation of nonself DNA on the body of the victim of strangulation. A similar caution should also be applied in the interpretation of DNA on the bra clasp.

In addition to the case study discussed by Wiegand and Kleiber, there are a small number of news reports of strangulations that mention DNA. One is from greater Detroit, and another is from Chicago. However, these articles do not specify the place on the body that was tested for DNA. In addition to the possibility that DNA was collected from the neck, it is possible that the victim’s fingernails contained the perpetrator’s skin cells or vice versa.

There are no reports that ILE found anyone’s DNA on Meredith’s bare wrists or her neck, and it is unclear whether or not the forensic police swabbed for DNA in these areas. It is also unclear whether some areas on the neck would have been free enough of Meredith’s blood to allow swabbing for the assailant’s DNA. Nevertheless it is difficult to see why the forensic police should not have swabbed the nape of Meredith’s neck or her wrists. If they did and found nothing, it would be strongly exculpatory, although it might fall short of proof of innocence due to uncertainties over collecting enough DNA or collecting it quickly enough after the murder. If the forensic police failed to swab these areas, it would suggest that they did not do as thorough a job as one would wish.

P. Wiegand and M. Kleiber, “DNA typing of epithelial cells after strangulation,” International Journal of Legal Medicine (1997) 110 :181–183. abstract

G. N. Rutty, “An investigation into the transference and survivability
of human DNA following simulated manual strangulation
with consideration of the problem of third party contamination,” International Journal of Legal Medicine (2002) 116 :170–173.

A. Lowe, C. Murray, J. Whitaker, G. Tully, P. Gill, “The propensity of individuals to deposit DNA and secondary transfer of low level DNA from individuals to inert surfaces.” Forensic Science International (2002) 129(1):25-34. abstract

E. A. M. Graham and G.N. Rutty, “Investigation into ‘normal’ background DNA on adult necks: implications for DNA profiling of manual strangulation victims.” Journal of Forensic Science, (2008) 53(5):1074-82. abstract