DNA Evidence

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The DNA Review

Stefano Conti and Carla Vecchiotti, DNA experts from the Sapienza University of Rome were asked to review the DNA evidence. Specifically they were asked to review the knife that was alleged to have been used to murder Meredith Kercher and a piece of Meredith's bra on which Raffaele's DNA was discovered. Because the evidence had degraded over the three and a half years since the original tests were done it was determined that Conti and Vecchiotti would be unable to redo the original DNA tests.[1] As such the expert's role was limited to reviewing the records from the original testing that was done under the direction of Patrizia Stefanoni.

The review was delayed but finally released and it was very critical of the work of the forensic laboratory under Patriza Stefanoni. This was widely reported but the content of the 145 page review did not live up to the media hype. Despite what was reported the DNA review did not "decimate" the DNA evidence. The DNA evidence had already been examined by nine experts including multiple defence experts. The idea that multiple defence experts would have failed to see major defects in the DNA evidence is simply not realistic. Despite that the media greeted the Conti-Vecchiotti review with unquestioning acceptance. It is impossible for anyone who has read the review and is familiar with Conti and Vecchiotti's testimony to believe that the DNA review had any impact on the reliability of the DNA evidence.

The Knife

Conti and Vecchiotti's criticism of the knife was two pronged. They start by claimed that since the DNA was LCN DNA it should not be accepted as reliable. They argue in the alternative that if Meredith's DNA is there it is likely from contamination.[2]

The issue of contamination is fairly easy to address. There are two ways that contamination could have happened - contamination at collection or contamination at the laboratory. The forensic team that searched Raffaele's appartment had no personel in common with the forensic team that searched the cottage. This makes contamination during collection impossible. Contamination at the laboratory would have been more of a concern except that no material related to Meredith murder was tested in Stefanoni's laboratory for the six days prior. Confronted with this fact that the lab had Carla Vecchiotti confirmed that contamination at the laboratory was not possible.[3]

For a detailed discussion of the The Double DNA Knife

The Bra Hook

The criticism of the bra clasp amounted to criticizing various minor procedural errors carried out during collection of evidence and extrapolating from that "anything is possible." This is a very weak argument. For example, one of the violations that the Reviewers point out is that a technician is seen not wearing a hairnet. While that is a lapse it can not be used to argue that it would lead to Sollecito's DNA appearing on the bra clasp. This is the core of their argument but none of the lapses they highlight have any possibility of leading to Sollicito's DNA ending up on the bra clasp.

What Conti and Vecchiotti are asking is for the court to accept that since these relatively minor lapses occurred then maybe even worse lapses occurred that we are not aware of. There is no reason to accept this assumption especially since Conti is unable to give an answer to what such a violation would look like other than "anything is possible." This is not something that a court will accept. If Conti and Vecchiotti could establish a possible but route for contamination that would go a long way to causing some doubt on the reliability of the DNA but they don't do this. Contamination given the lack of a source for Raffaele's DNA and given the quantity of DNA makes Conti and Vecchiotti's claims of contamination too improbable to accept.

Conti and Vecchiotti also claim that Stefanoni was incorrect to classify some peaks as stutters. They base this on a strict mathematical application of the height threshold. This is not generally accepted by DNA analysts but Conti and Vecchiotti present it as if it is.

For a Detailed Discussion of the Bra Clasp

Additional Criticism

Failed to Compare Stefanoni's Work to the Standards of the ENFSI

The first criticism is that Conti and Vecchiotti did not do the task they were assigned by the court. The role of the DNA review was to determine if Stefanoni adhered to the standards of the accepted regulatory framework. Instead Conti and Vecchiotti embarked on a task of creating their own standards pieced together from various academic sources. Stefanoni maintained that she adhered to the guidelines of the ENFSI and that Conti and Vecchiotti's criticism that she did not follow the procedures of some other body is not relevant. Conti and Vecchiotti are not members of the ENFSI[4] which makes their selection by Judge Hellmann difficult to understand. The purpose of the DNA review was to assure that Stefanoni adhered to the ENFSI and as such should have been done by someone who was certified by that regulatory body.

Suspicion of Defence Interference

One of the first things that sticks out about the Conti-Vecchiotti Report is that they source numerous US sources[5] that have no relevance to a murder that happened in Italy.

This quickly led to suspicion that Conti and Vecchiotti were being fed information by Knox's defence team.[6]


  1. Squires, Nick."Amanda Knox appeal receives fresh impetus from forensic review" The Telegraph 24 March 2011.
  2. Kington, Tom Amanda Knox DNA appeal sparks legal battle by forensic experts The Guardian 24 July 2011.
  3. Staff. [http://www.repubblica.it/cronaca/2011/07/30/news/meredith_processo-nuovo-19812721/ "Meredith, periti Dna in aula Il coltello non fu lavato"] la Repubblica 30 July 2011
  4. Kington, Tom Amanda Knox DNA appeal sparks legal battle by forensic experts The Guardian 24 July 2011.
  5. Kington, Tom Amanda Knox DNA appeal sparks legal battle by forensic experts The Guardian 24 July 2011.
  6. Kington, Tom Amanda Knox DNA appeal sparks legal battle by forensic experts The Guardian 24 July 2011.