Ummm, you have the chain of events backwards. Raffaele invented the "I pricked Meredith with the knife while we were cooking together, then I apologised to her" (my paraphrase) only after police had seized the Double DNA Knife. It was his reaction to realising that the police had the evidence.
As for a "random grab", if you look a images of Raffaele's kitchen cutlery drawer, you'll see that the Double DNA knife was the only one which could have been a useful weapon. Otherwise there was a bread knife and unthreatening normal table knives.
Well, he had a bunch of knives a whole lot more useful for cutting people than chopping onions, those would have been the obvious ones to check. However when did they get the forensics back? When did they 'know' Meredith's DNA was 'on' that knife? It's a minor point at any rate, I'm just speculating how they might have chosen that one which turned out to be so embarrassing to them.
Because, it wasn't the murder weapon, it didn't match the outline left, it didn't match most the wounds and the other could have been done by anything from a box-cutter to a broadsword--including the actual murder weapon. All that knife amounts to is evidence against the prosecution's rush to judgment. If by some unlikely transfer or contamination it actually bore Meredith's DNA, despite the prosecutions' unwillingness to prove that, it still couldn't have been used by Amanda or Raffaele in that room, as the absence of any other sign of them speaks volumes. Unlike logic, in this case absence of evidence
is evidence of absence.
What the bra clasp and 'murder knife' actually prove is that the prosecution was so desperate to tie them into that room they had to bring items from outside the room or those obviously contaminated. They also eliminate the possibility that there was Amanda and Raffaele's DNA in that room, the forensics team just missed it, statistically highly unlikely with all they found of Rudy Guede's but barely possible--until the bra clasp and 'murder knife' show what lengths they went to in the attempt to find something of Amanda's or Raffaele's in that room.
At any rate whatever was on that knife and bra clasp the one thing you know for sure it wasn't is evidence of murder. That would require evidence of Raffaele and Amanda at the scene, and the handful of picograms of whatever on the knife and clasp certainly doesn't qualify as anything but a desperate attempt to fool credulous people.
Your "obvious" description seems only obvious to FOAKers. Not even Amanda's lawyer Ghirga dabbled in speculation as to what the state of Filomena's room represented.
I don't understand what you're getting at. If there's a break-in and a girl killed, it takes a special kind of mind to come to the conclusion it had to be staged and when the 'evidence' of that is ridiculous assumptions like a burglar couldn't break in to a second story building they've failed in their quest to prove the counter-intuitive.
As for Satanism and esoteric rites, if you read the Massei report, you'll see that it was not mentioned once in the trial, nor in the formulation of the judicial opinion. That's good news, as that means that FOAKers and The Entourage can stop talking about Satan.
I'm talking about the initial 'theory' that Amanda, Raffaele and Patrick were arrested under. The one broadcast to the press.
Again, please review the facts. If the police "zeroed in" on Patrick, it was because Amanda had (falsely) accused him.
No, she didn't. She had the screws put to her for hours and finally succumbed to suggestion. They already had her phone wire-tapped, they already suspected Patrick. If they asked her about the SMS message and she replied who it was, then perhaps she spoke his name first, but that they claimed they had a kinky black hair, (which apparently never showed up in evidence) and were interested in that SMS and lied to her telling her they had video evidence of him going into the building shows who they were interested in.
The "several" people was the Swiss professor who had to be flown in for his testimony. In the meantime Amanda did not lift a finger to write yet another spontaneous declaration in order to deny what she had earlier stated to the police concerning Patrick murdering (according to her) Meredith.
Actually she did, and there's not much more she could have done all locked up like that. At any rate the idea that a professional police force moves on the 'repressed memory' of a traumatized girl heavily interrogated and lied to regarding 'evidence' of Patrick at the scene and her boyfriend claiming she wasn't with him is ludicrous. That they tried to 'blame' it on the twenty-year old girl is simply more evidence of CYA on the part of the Perugia police, and invites further inquiries on what else they tried to hide in the course of botching this investigation.