This is pretty much what site administrator from PMF.net, Michael has written. I don't know how to do spoilers, so here it is:
"Just a thought out loud. As regular readers here will know, over the past year or so I have changed my mind about the murder from originally considering it to be a nasty prank/hazing gone wrong or gotten out of control, to premeditated murder. At least by Knox, and I felt "probably" also by Sollecito. I did not believe this was the case with Rudy and that remains the same. I have however, adjusted my view to now be certain in my own mind, that it was was also premeditated for Sollecito.
As some have may recall, I believe Rudy was only present at the start of the attack and for the sexual assault but was not present the whole way through. For a range of reasons, I adopted the theory that shortly after the sexual assault, which I think was mercifully brief (although, of course, still terrible for the victim just the same) and not carried out with any enthusiasm by Rudy, realising that this wasn't what he'd signed on for, wanted out and left Meredith's room to take up temporary residence in the large bathroom over the other side of the cottage. This transfer would have taken place before any blood was spilled. It was then some minutes later that Rudy was alerted by the scream, rnb from the bathroom to Meredith's room to be confronted by carnage.
I still hold to this theory. But, one element of it I am now questioning in light of my post a two posts upthread were certain pieces of the puzzle slotted into place for me. The element I am now questioning, is whether Rudy unilaterally removed himself from the room to the bathroom. I am now wondering, if he was actually instead sent by Knox and Knife Boy. I am asking this, as I feel Rudy was recruited to play a certain role and that was to help initiate the attack to subdue the victim and to then carry out a sexual assault (although, I feel the others wanted Rudy to go further then he did). Once that had happened, his job was done, he was no longer needed as the rest the other two could do themselves. Nor do I think was he was even wanted. He was not part of the pact and so at best, he would have been intruding on their final act. At worst, he could potentially have interfered or even tried to stop them, as he had not been told this was intended to be a murder. Moreover, Knox and Sollecito could feel safe in sending him elsewhere in the cottage and carry out their murder confident that Guede wouldn't later be volunteering information to the police, as they had made him take part in enough of the attack to ensure that under the strict definition of the law, he would be regarded as being as guilty as they (and there is no plea bargaining in the Italian system for felonies and capital crimes). It may still actually be the case that Rudy left the room unilaterally, but in that event, I feel that if he hadn't of done so of his own accord he would have been dismissed. He was never given a knife, as they never intended for him to be present or active in the final act.
There was one serious way the pair, who were in full control of the situation from the start of the attack right up to the murder itself, made a fatal error shortly after that would have ensured that eventually, they would be caught. I've never seen this discussed before now. This fatal error, was their failure to control Rudy in the immediate aftermath of the murder. Rudy attempted to help Meredith and in so doing, he got blood on his hands which he then transferred in the form of his fingerprints and DNA to the outside of Meredith's handbag while moving it and his bloody hand print with his fingerprints onto the pillow. In addition, his bloody shoe prints in the hall which while they specifically would not have the potential to lead to Knox and Sollecito being caught, they would provide important details about the context and narrative of the crime, which once they were caught, would contribute to convicting them. You see, the key evidence left at this point, was the DNA and fingerpints. Had Knox and Sollecito done a better job with their lies and alibis and so were not arrested on the 5th Nov, they still would have been doomed. All that was required was for either Guede's DNA or his fingerprints to be on file (it turned out, his fingerprints were indeed registered with his identity card application) then that would have directly led to Rudy's identification and arrest. Rudy's arrest would then have led to Knox and Sollecito's arrest, as one can bet facing the blame all alone he would have swiftly pointed the finger at them. As it turned out, this never needed to happen as Knox and Sollecito had failed to flesh out their alibis and they were arrested before Rudy. But it doesn't matter, even if they had of avoided arrest they were always doomed because they had made the mistake of allowing Guede to help Meredith and then right after, interact with items in the room leaving key evidence that would lead to his identification. This mistake, meant all their partial cleaning, staging and lies, even if dome competently enough to send the police off track, would always have eventually failed due to the presence of Rudy's fingerprints at the crime scene."