Can't really dispute much of what you're saying, since it's pretty much personal opinion and reflection. I will, however, address a few points:
Believe all you want, but you can't really expect rational people to follow down this same path of implausibility. OK, let's allow for the possibility that one piece of evidence is the result of contamination (and possibility is all it is, since there's zero proof that this is the case). But all the above evidence is the result of contamination?? What are the odds of so much key evidence being completely spurious? Just how unlucky can a person get? Sorry, but there's no way happenstance produces a string of false evidence like that all pointing the same way. So you're left with either it's all the result of a conspiracy (there's that word again), or...she did it.
Granted. But to do that with any efficacy, it isn't enough to present conceivable alternatives to individual pieces of evidence. You also must present a reasonable alternative scenario that explains all the evidence. In my opinion, thus far Knox supporters haven't even remotely come up with one.
And as far as Knox's lies are concerned, I think it's disingenuous to attempt to dilute their import with judicial trivialities. The fact is, she falsely (and quite voluntarily) accused someone she knew was innocent of Kercher's murder. The fact is, she did that for a reason. And the most obvious and plausible scenario is that she did it because she's guilty and attempted to divert police attention away from herself (which initially worked, however briefly). Sure, I suppose someone can come up with some extremely far-fetched alternate reason Knox might innocently tell such a lie, but it detracts not one iota from the fact that her lie is perfectly consistent with the police version of events, namely...she did it. Sorry, you just can't hand-wave this fact away, not if you're genuinely concerned with the truth.
Who said anything about all the key evidence being the result of contamination? Not me. And much evidence can be made to point in a number of differing ways - so to state that it all "points one way" is disingenuous and misleading.
It isn't the job of the defence to present an alternative scenario which explains away
all of the prosecution's evidence. I thought you might know that, from the surety of language used in your post. It's the job of the defence to construct reasonable alternative explanations for enough areas of the prosecution's evidence so as to introduce reasonable doubt in the case as a whole.
As an example, let's say that Mr A was on trial accused of murdering his wife. Mr A worked in an office 5 miles away from his home, and his wife was killed at 11am on a working day (time established definitively). Let's say that the prosecution offers only two pieces of evidence against Mr A (for the sake of simplicity), which comprise two witnesses:
Witness 1 lives opposite Mr and Mrs A's house. He says that he was mowing his front lawn that morning between 10.30am and 11.30am. He's sure of the time, since he went out to start mowing as soon as his favourite daily soap opera (which he never misses) finished at 10.30, and he knows that his front lawn takes an hour to mow. He says he saw Mr A arrive back at his house by car 20 minutes after he started mowing, and then he saw Mr A leave the house by car 15 minutes after that. He saw nobody else arrive at the house either by foot or vehicle during the period he was outside.
Witness 2 is a restaurant waiter who says that he overheard Mr and Mrs A arguing loudly and bitterly in his restaurant the evening before the murder. He says he heard Mrs A say that she was going to divorce Mr A and take him for everything she could get.
Now, let's say that the defence manages to successfully discredit Witness 2 (maybe they can show that his shift started after Mr and Mrs A had already left, so he must have seen another couple arguing). But if they can't discredit Witness 1's testimony in any way, it's quite likely that a jury would find Mr A guilty of murder. After all, Witness 1 provides strong evidence that Mr A returned to his wife's location exactly over the time of her murder, and left shortly after, and that nobody else was seen to come or go to/from the murder house over this period.
However, imagine if the
opposite happens: the defence manage to successfully discredit Witness 1 (maybe he was elderly and had confused his days; maybe the defence finds a local council employee who can prove that he was mending a street light outside Witness 1's house on the day of the murder between 10am and 10.50am and who can testify that Witness 1 was not mowing his lawn on that morning). But in this scenario, the defence cannot discredit or refute the testimony of Witness 2.
In this second scenario, the defence have once again discredited one area of the prosecution's evidence, but not the other. But this is where the relative importance of evidence comes into play. Without a witness who can place Mr A as the only person entering or leaving the murder house over the time period when Mrs A was killed, the prosecution's case sinks. Witness 2's testimony is interesting, but it's not any kind of proof of murder. Mr A would almost certainly be acquitted by a jury in this scenario.
Can you see now how it's not necessary for the defence to demonstrate fallibilities in
each and every piece of the prosecution's case in order to show reasonable doubt in the case as a whole?
