forensic bias
But my response wasn't to a claim of investigator bias, but to contamination and the point still stands. If Amanda's and Raffaele's evidence was all contaminated, why wasn't Rudy's also?
You've also yet to prove investigator bias. Moreover, the basis of your claim isn't fully correct in any case. A large amount of Rudy's evidence wasn't processed until after his arrest...it took them over three months to process all the forensic evidence from the case.
I also fail to see why just because they had Amanda in custody, that means evidence collected or examined would be done with bias. And as far as I'm aware, Dr Stefanoni hadn't even met Amanda or Raffaele. She didn't care whether they were innocent or guilty. Her sole job was to analyse the data.
I also can't see 'how' bias can come into play. It's either Amanda's DNA on the knife handle and Meredith's DNA on the blade, or it isn't. Even the defence don't dispute it isn't. It's either Raffaele's DNA on the clasp or it isn't. The footprints are either a match fro Amanda, Raffaele and Rduy or they are not. It's either Amanda's DNA mixed with Meredith's blood or it isn't...and so on.
Fulcanelli,
With respect to contamination, there are several factors to consider. First, I have long pointed out that contamination can be sporadic, which (among other things) makes negative controls less useful than they would be otherwise. Second, I have not seen the electropherograms with Rudy’s profile. If they contain the same problems as are in Meredith’s profile on the knife and Raffaele’s presumed profile on the bra clasp, then the caveats I have raised about these two items carry over to the other samples. Third, the evidence against Guede is fundamentally between Guede and his lawyers versus ILE. If they did not dispute the data, I cannot offer a different opinion without more data. Fourth, contamination is not the same thing as secondary transfer, as I made clear to Stilicho many months ago on the previous thread. I am not sure that the bra clasp, for example, was contaminated; both secondary transfer and evidence tampering exist as possibilities.
With respect to showing investigator bias, please see my previous comments on evidence item 164. Dr. Stefanoni stopped testing on this sample, yet she continued with the knife. Do you have a better explanation than investigator bias?
Investigator bias can come into plays in many areas of forensics, as the citations I have previously given (Koppl's "CSI for Real," for example) demonstrate. One is in the use or misuse of a suspect’s reference profile to interpret an evidentiary sample, as Dan Krane and colleagues discussed (
Journal of Forensic Sciences. 2008;53(4):1006-7). The interpretation of mixed DNA samples is also not completely objective. I have given citations on this subject within the last couple of months, and the disagreement between Dr. Stefanoni and the more conservative Dr. Tagliabracci as discussed in the Massei report illustrates this problem nicely. One way in which bias can come in is to diminish the importance of real peaks because they do not fit Raffaele’s profile, as Dr. Tagliabracci implied that Dr. Stefanoni did (see my comment last week or so).
The DNA testing started as early as November 9, 2007. Although it may have been completed after other forensic testing was, that does not alter the fundamental principle that forensics of various hues showed that Guede was in Meredith’s room and elsewhere when he had no business being there. By the time of the initial DNA testing, the police had declared the case to be closed and paraded the suspects through the old town of Perugia. The police, PM Mignini, and Dr. Giobbi had all put down their markers with respect to Amanda and Raffaele. In addition, it is incorrect to say that Dr. Stefanoni’s sole job was to analyze the data. She also took part in collecting the data. She asked for and received special permission to do so, a departure from normal policy (IIRC, Darkness Descending mentions this).
When the investigators fail to collect footprint references from Laura and Filomena and then want me to believe that Amanda made them, I call bias. The lack of obtaining reference DNA from them is almost equally mystifying.
Bias also comes into play in other ways, such as how one
interprets the data, as much as anything. It may have led Stefanoni and others to impart a significance to the mixed DNA samples that simply is nonexistant.
It has to be among the most unsurprising results of all time that Amanda’s DNA was found in her sink. I would have been a little surprised it if had not. If someone still wishes to claim that the mixed DNA samples mean anything, I would ask them to interpret the significance of samples 93 and 95, which are mixed samples of Raffaele and Amanda, from Raffaele’s flat.