Reading the comments on Rudi's blood reminded me of Massei's logic on the clean-up. You know stuff wasn't there so it must have been cleaned up. In this example he must have bled so they must have found it or at least it must have been there. It made me wonder at what point Stef decided to stop producing evidence for the unknown perp and how she covered up what was found after that perp was in custody.
He [GUEDE] was cut.
It either happened during the attack, as he said, or sometime later as you seem to want to believe on the basis of a witness who said merely that he spent 30 minutes watching tv with Rudy the next day and didn't notice any cuts.
The evidence doesn't require an immediate, active conspiracy, as you seem to be suggesting. Let's look at the where Rudy's blood likely was:
1. Knife handle: The imprint on the bed sheet was not tested for DNA. Incompetence.
2. V-Swab: No test for blood done; Stefanoni much later testified that the DNA was from skin cells, without explaining that she had no way to determine this or allowing that it could have been blood. Incompetence/Dishonesty.
3. Palm print: Not tested for DNA. Incompetence.
4. Purse: This was blood positive, and showed a mixture of Rudy/Kercher DNA. Fine.
5. Bloody towels: Not tested before spoliation. Incompetence.
6. Bra, Kercher's trousers, sweatshirt, handprint on wall: Need to further research these.
7. Downstairs: Suppressed. Dishonesty.
8. Stuff in Rudy's flat: Some blood positive; much suppressed. Dishonesty.
So, by my tally, most of the above is attributable to incompetence, except the results from the vaginal swab, Downstairs and Rudy's flat.