The only DNA evidence at the scene was found on a bra strap collected
47 days after the murder when the crime scene had been totally compromised. Countless experts in crime scene examination have noted the poor working practices of the investigators. There is even video evidence of these practices, where blood gets on their gloves before they move to another location and do not change gloves.
All DNA from Knox was found in the bathroom she shared with Meradith. Rudys DNA was all over the scene.
This outlines some of the details:
The bra clasp
That's not entirely true. There was a knife found which had DNA of the victim on the blade, and Knox on the handle, although the DNA sample was limited.
Knox testified that a smear of her own blood in the bathroom was not there on the afternoon of the murder. Various bits of the bathroom tested for mixed dna profiling of diluted blood; which is totally possible in a house, I know.
There are lots of odd goings on with the footprints which seem to indicate that Knox's feet had blood over them. The court decided there was no other time when this could have happened other than during the murder/cleanup... I'm honestly not sure.
The whole thing just seems very iffy; there's tonnes of misreporting going on, Knox's story changed multiple times, was there actually a break in? I don't have an actual view as to whether she was involved or not but she certainly has done herself few favours if she is not.
A delay in collection also is not all that problematic in itself; DNA evidence is routinely used worldwide for items a lot older than that. The bra clasp was not moved from Meredith's room; how did Sollecito's dna get there at all? The only other sample of his DNA was on a cigarette butt in the kitchen. It's just odd, and doesn't seem to add up from any angle, guilty or innocent.
The low amount of defensive wounds also indicates it was likely that meredith was restrained while the killing was going on... not for sure that it was Knox and co, but interesting nonetheless.
In addition, this 'satanic ritual' crap that keeps coming up is not mentioned in court reports; it was first claimed by Sollecito's defence lawyers, and the prosecutor and judge both deny this being made as an allegation. The judge's conviction report makes zero mention of it and as such it was not taken into account when convicting.