In fact I am specifically talking about lines of defence.
Reasonable doubt is a criterion for the judge, but it is also a possible line of defence. And this is what I am talking about.
Because I am talking with advocates, who are basically pushing a defensive argumentation.
Such argumentation is theoretically a possible defensive argument.
What I am saying is that the arguments brought by the advocates are not effective a holding this line of defence.
Things like criticising the fact that Stefanoni didn't prove she had clean gloves, is not a kind of argument capable of producing a reasonable doubt.
So the general rule: a mere observation about the fact that pieces of circumstantial evidence are not perfect, itself is not a logical argument for reasonable doubt.
It is not true that the accusation (prosecution but also judges and parties, not prosecution alone) must overcome reasonable doubt on single pieces of evidence. The concept of reasonable doubt applies only to the comprehensive set of the whole evidence, whereas the existence of limits or imperfections of the single pieces of evidence, itself is not an argument capable to hold back against the set of evidence overall.
A set of imperfect pieces of information - pieces that have "holes" - under the logical point of view, is perfectly able to support a conclusion that has no doubt nor holes.
This is a rule of logical inference, and it is the concept at the root of circumstantial evidence.
See highlighted parts. Machiavelli, you are mixing logical categories, but then what else is new.
It is up to any collector of evidence to be used at trial to demonstrate that protocol was followed. But please note how you change the logical goal-posts above. No one is arguing for perfection (so there goes your strawman argument).
There is ALWAYS the possibility that even following protocol produces contamination.... however, if the protocols could be shown to be followed, even that evidence so collected would be admissible - albeit challengable on other grounds.
What is unique about this case is that obviously (proof being the Scientific Police's own video, for pete's sake) that protocol was NOT followed. Even you have to find a way to justify an obviously dirty glove....
Your explanation is that the clasp contaminated a formerly clean glove!!!
(Let's just leave that jaw-dropper for a minute so that the point in question does not get lost! But I cannot believe your "narrative of the crime" includes a contaminated/dirty bra-clasp soiling an otherwise clean forensic-glove 46 days later!!!!)
You are correct about one thing. The concept of "reasonable doubt" belongs to the whole.... but it also means that if one or maybe two key pieces of circumstance cast doubt on the whole, then (in most jurisdictions) a trier of fact would be required to acquit on that alone.
So - it is illustrative the way you need to argue to try to finesse this point. No one is arguing for perfection. Even protocols allow for the possibility that all can be followed to-the-letter, and contamination can still sneak through, through some unknown means. (And, no, the defence is NOT required to explain how, if, indeed, contamination is found.)
The "evidence set of the overall" can, and often does in democratic systems, be ruined by one or two bits of circumstance which tend to cast doubt on the whole. True, "reasonable doubt" is applied to the whole, but reasonable doubt requires that the whole be able to withstand the doubts any one bit of contrary evidence contributes.
Which is my way of saying - man oh man, you have a strange way to try to bolster your point by choosing Stefanoni's glove as the analogy.