Massei’s reasoning on the clasp looks worse and worse each time I read it. He wrote, “Moreover, they [note: Stefanoni’s explanations and answers] were also considered acceptable by the defendants’ defence teams themselves for the greater part of the results which the Forensics biologist had obtained. This refers in particular to all the traces, but not just those, of Rudy Guede, the results of which were fully accepted and in relation to which the defence teams had insisted on the theory of Rudy Guede’s responsibility and, it must be added, Dr. Stefanoni (in examining specimen 165B) did not change either the methodology or the interpretive criteria.”
The first problem with his argument is that it ignores that the clasp was a mixture, unlike many of the other samples, and mixtures are more subjective in interpretation. The second problem is that Dr. Tagliabracci is not Rudy Guede’s expert witness and may never have seen the electropherograms related to his trial. I cannot speak for Dr. Tagliabracci, but I accept the DNA forensics evidence provisionally because I have never seen it myself; if it were as flawed as the clasp profile, then the DNA evidence against him would be equally weak.
More generally, the pro-guilt advocates and Barbie Nadeau have an argument that runs something like the one offered by Massei: You accept the (DNA, shoeprint, footprint) evidence against Guede, yet the same forensics team that collected evidence against him collected evidence against Knox and Sollecito. Therefore, you are being inconsistent in rejecting the latter evidence. The errors in this forensic fallacy ought to be made explicit: First, it ignores when the evidence was collected. The forensic data made Guede a suspect, but Sollecito and Knox were already suspects by the time the forensic data were interpreted. Thus cognitive bias could only come into play for Knox and Sollecito, but not for Guede. Second, the pro-guilt argument pretends that all forensic evidence is equal in quality, but we know that this is not the case with the bra clasp or the knife profile. Third, this argument could be extended to pieces of evidence that was initially contested, but no longer are. For example, the prosecution could have said to the defense that the defense accepts that Guede’s shoes made the prints in the hallway; therefore, it should accept that Sollecito’s shoe and Amanda’s shoe each made a print in Meredith’s room. Yet it is now clear that
all of the prints belong to Guede; even Massei does not definitively attribute to Sollecito the shoe print ILE formerly did.
The fallacy becomes more obvious when one considers the converse. One could argue with equal validity that ILE’s forensics team was wrong about the shoe prints; therefore, they are automatically wrong about everything concerning Knox and Sollecito. If that argument does not make sense, then neither does Massei’s.
