Part V in a series on the Knox/Sollecito case
Meredith Kercher’s bra clasp was separated from her bra, presumably by the murderer. The first problem with the bra clasp in this case is the fact that it was not collected as evidence until about 47 days after the crime, on 18 December 2007. This might not matter if the crime scene had been secure. However, someone had moved the clasp had from its original location (by a meter in some estimates). Someone had broken into the house on two separate occasions in early 2008, after the clasp was in police custody. The lack of control over the bra clasp alone might be enough to disqualify it as evidence.
A second problem is that the clasp became dusty because it was found in a pile of clutter. Human epithelial cells are a major component of dust; indeed, dust itself has recently become of forensic interest (http://www.newscientist.com/article/mg19826584.200-telltale-dna-sucked-out-of-household-dust.htm). A third problem with the clasp is that it was handled with dirty gloves. Here is a video that documents this fact, as well as the dust on the clasp itself:
The glove might have touched the same door or door handle that Raffaele Sollecito used when he attempted to break the door down after Meredith’s murder. This is one possible route of secondary DNA transfer. In addition, note how it was treated in a second video:
The clasp should have been handled with disposable tools. Moreover, the clasp is being passed to and fro unnecessarily, and even put on the ground, both of which increase the likelihood of contamination. One wonders why the clasp is being put on such an elaborate display.
The mixture of DNA
The clasp had Meredith’s profile as the strongest component. A relatively weak component (200 relative fluorescence units) appears to be Raffaele’s DNA. There are reports of DNA from at least three other people (http://www.dailymail.co.uk/news/article-1234298/Amanda-Knox-The-troubling-doubts-Foxy-Knoxys-role-Meredith-Kerchers-murder.html
The 19 November 2009 letter coauthored by Drs. Hampikian and Johnson said, “Transfer of Raffaele’s DNA to the clasp could have occurred through several innocent means as a result of his DNA being in the apartment or via Amanda’s clothing or belongings. DNA testing cannot determine how biological material was deposited onto an item of evidence: whether by direct deposit, or by secondary transfer through an intermediary. DNA testing cannot determine how long biological material may have been on an item, or whether contamination occurred during collection.”
The presence of a mixture leads to several questions. First because I cannot envision how so many people could have handled the bra clasp directly, I think that indirect transfer of DNA is the more likely explanation. Second, it is difficult to see why the three individuals who deposited DNA on the clasp should not be considered potential suspects. Third, suppose that the police had taken other dusty items into evidence at the same time as the bra clasp. If these had been utterly clean of DNA, the results on the clasp would carry more weight. From what I can gather, no such items were taken into custody on the same day.
The lack of other DNA
At a pretrial hearing Mr. Sollecito’s defense team argued that the lack of his DNA on the bra itself is significant (http://www.telegraph.co.uk/news/3255101/DNA-on-Meredith-Kerchers-bloodied-bra-was-due-to-lab-contamination-claims-Sollecito.htmlhttp://www.telegraph.co.uk/news/3255101/DNA-on-Meredith-Kerchers-bloodied-bra-was-due-to-lab-contamination-claims-Sollecito.html), “But defence lawyers used a mannequin's bust and a white bra to argue that it would be impossible for Mr Sollecito's DNA only to have ended up on the tiny clasp and not the rest of the bra if he had touched it or handled it.”
The Hampikian/Johnson open letter said, “Neither Raffaele Sollecito’s nor Amanda Knox’s DNA was found on: the remainder of the bra that was found with the victim, other items of victim’s clothing, objects collected from the room where the victim was found, or in samples from the victim’s body. These evidentiary samples were all collected the day the body was discovered.”
The lack of Sollecito’s or Knox’s DNA on anything in Meredith’s room except the bra clasp is hard to square with an attack that the prosecution claims to have lasted at least 20 minutes.
The main issues I have with the clasp are that it must have been handled by at least one unknown person, that it picked up dust during the 47 days, and that there are deposits of DNA from other individuals on it.
The Johnson/Hampikian letter deserves the last word: “Handling and movement of this sample has compromised its probative value. The laboratory results for this sample cannot reliably be interpreted to show that the DNA of Raffaele Sollecito was actually on the bra clasp at the time of Meredith Kercher’s murder, and it does not establish how or when this DNA was deposited or transferred.”