Welcome back, Machiavelli. I see your memory has failed you (again!). Here is where Massei renders Stefanoni on this point:
I see that someone
here has thoughtfully archived the actual testimony Massei paraphrased above:
Now if you read the rest of that page you'll see that in batch 4, well B11 showed a count of 34.30, meaning on the 34th cycle it registered human DNA as opposed to going 50 cycles without finding any which is what is supposed to happen, being as it's a negative control and there should be
no DNA in it at all. In addition there were over a hundred samples with human DNA where the results were withheld, some of those quite likely because they'd show the copious contamination in that lab which would show up employing
LT/LCN protocols. (...)
Let's stop here first, and answer this point alone to avoid too long posts.
Well, no, no no. I think you develop your own concept of “contamination issue”, and probably that's the problem.
It would be better instead to look at what Stefanoni says altogether; and it’s better to use the information for building arguments that make sense. Stefanoni says some other, very different things, where she explains how negative controls work, she explains that the possibility of contamination in reagents - whether you see it as "contamination" by a whole profile or instead by single drop-in allele - in negative controls, is something that can always happen. This kind of contamination happens, the possibility of contamination is something “normal”, therefore the negative controls are part of the work.
Let's quote Stefanoni (Oct. 4. 2008). Sorry, I must quote he testimony in Italian:
Stefanoni Oct. 2008. p. 50 said:
...Non condivido la metodologia, noi i controlli negativi li utilizziamo nella nostra pratica di laboratorio ma hanno un altro significato, li utilizziamo per esempio in qualunque fase di lavorazione dall'estrazione del campione biologico fino all'analisi elettroforetica perché? Perché in quel caso a noi interessano due cose: una vedere la bontà dell'esecuzione da parte dell'operatore sulle metodiche che prevengono un possibile inquinamento e quindi un possibile trasferimento di proprio D.N.A. dell'operatore al reperto, perché anche questo è possibile, inavvertitamente fare, nonostante tutte le precauzioni, e a tal scopo ogni operatore infatti è tipizzato cioè si conosce il suo profilo genetico in modo che se, come spesso accade, i profili genetici sono di persone ignote noi sicuramente possiamo escludere che quel profilo genetico ignoto non sia magari di un operatore tecnico o di un'altra qualunque persona che sia venuta a contatto con il campione stesso. Poi un altro controllo che noi mettiamo come negativo, che noi chiamiamo “bianco”, è un controllo che serve a verificare che praticamente, come dire, i reagenti utilizzati - perché si utilizzano reagenti chimici in tutte le fasi di lavorazione naturalmente, perché è un processo chimico sia l'estrazione che l'analisi del D.N.A. - non abbia esso stesso delle contaminazioni accidentali dovute a precedenti operazioni di prelievo, per esempio di una aliquota, perché i reagenti ovviamente non sono monodose, i reagenti devono essere presi ogni volta dall'operatore da una provetta, un tubino perché si usano in piccolissime quantità nell'ordine dei micro litri che ! sono un milionesimo di litro quindi una cosa assolutamente molto piccola per cui quella provetta viene utilizzata più volte, per cui il nostro controllo negativo, per esempio nella fase di amplificazione, è quella di osservare avendo messo tutti i reattivi chimici tranne il D.N.A., non mettiamo nessun tipo di D.N.A., che quel campione una volta analizzato non dà nessun segnale di D.N.A. ovviamente(...)
I don’t know what “contamination issue” would mean according to you (and I don’t think the defence lawyer has a precise, technical meaning in mind neither), but what I understand from Stefanoni’s explanation, is two things: first, that the contamination of a testing tube with an extra-profile (from a technician for example) or with the drop-in from an “aliquota” (a modicum, a small fraction) of the reagent that was used in the previous test with the same test tube, is to be considered relatively “normal” possibility (not something that you don’t meet for seven years). Second, as an implication of this, the meaning I understand she gives to a concept like “contamination issue”, is that you can deduce from what she explain, to say a DNA finding in the laboratory was due to “laboratory contamination” (there is an issue) is something that does not equate to mere “presence of an allele peak in a negative control”. You can well infer from what she says that, in order to say “this profile was contamination”, you need to have in your negative control something that yields a positive result that is significant, and possibly about the profile itself; it means that the profile extracted from the sample analysis (or most of it) is found in the negative control as well, so that you may conclude: the DNA did not come from the sample, it is found everywhere in controls so the reason must have been the reagent that was not “clean”.
I don’t think anything like that comes out anywhere in the DNA findings.
I also know that prof. Novelli testified that he analyzed a sequence of 105 tests carried on within a week with the machine that tested the knife, and he found no trace contamination. I also know that nobody, either Vecchiotti or the defences could disprove or dispute Novelli’s statement.
So, what I see is that you are making up technical meanings, creating conditions, which in reality they do not belong to the true technical meaning. You say "in a negative control and there should be
no DNA in it at all", and this appears to be just plain false. You use this false premise in order to build a conspiracy theory (at the same time, you delete parts from the meaning of what Stefanoni said). Don’t misunderstand me: by putting this objection to you about the flawed premise, I am not just limiting the focus on considering what Stefanoni says, I am not picking up the corret premise from Stefanoni alone; you could equally deduce the same, more correct premise regarding drop-in alleles in negative controls, by picking quotes from Vecchiotti as she quotes Caragine et al (translation of C-V report, p. 94):
C-V report p.94" said:
Moreover the experiments done have shown that, despite the scrupulous application of adequate protocols in order to minimize the possible sources of alleles drop-in within the laboratory, anyway we should always expect to observe a few extra alleles in negative controls.
You can see Vecchiotti quotes Caragine, saying - read carefully the wording - one should
always expect to find a few extra alleles in negative controls.
Always. This as for Caragine and Vecchiotti seems to agree.
Vecchiotti also pointed out that currently
no protocols have been developed in order to how to "count" the drop in alleles to the date in order to assess the quality of negative controls (p. 90):
(…) there has not been a discussion yet about the number of negative controls that should be analyzed in order to verify the randomness of the drop-in phenomenon (…)
So your first assumption, that "there should be no of DNA trace at all", not even a single drop-in allele in a negative control (I believe actually B11 is a negative sample rather than a negative control but it makes no big difference), is simply false. The ngative controls should have a good quality, but you should
always expect to find a few drop in alleles (this is what I can read in reports and testimonies).
Last thing, I point out that there are no DNA profiles that were "withheld". Not even one. All documentation about all results that was requested - and btw all of what was requested was requested anyway
late according to what the procedure code provides for - was all given. What was not given is what had just never been requested, certainly not within the timings and fashion in which it was offered according to the procedure code.