I'm pretty familiar with this case having read a couple of books about it and followed both of the websites listed and a few others.
I would say there is 0 chance of Knox or Sollecito being involved in the murder at all. They have no motive. The prosecution completely failed to show that they had ever participated in "sex games" together or with different partners in the past. There is no evidence of either of them at the crime scene at the time of the crime. None of their past behaviors make them likely candidates to commit this type of crime. Ev...
Why? What negative result follows when you assign probability zero to something? I haven't consciously experienced any so far.