In order to understand why the Italian "justice" system allowed Mignini to put so many people through hell, and to waste so much time and money, you must recognize that "Satanic ritual abuse" is meant in the sense of being repetitious, like a morning ritual, not in the sense of being ceremonial. SRA can consist of ANY FORM OF GRATUITOUS CRUELTY, as long as it remains hidden or can be explained as something else, and it's most effective against KNOWN INNOCENT PEOPLE such as Knox, Sollecito, and Lumumba, for simply being human. Mignini himself said that Knox was unknowingly part of a Satanic ritual, referring to what HE (and his fellow Satanists within the Italian "justice" system, and organized Satanism all over the world) were doing to HER and her sympathizers. "Guilters" don't really believe she's guilty - they're lying in order to torment her.
The main purpose of SRA is to open the perpetrator's soul to demonic possession, although they're naturally not told this. Crowley, in The Book of the Law, admitted that he could not admit the real reason for SRA: "Enough of because! Be he damned for a dog!" Instead, they're told they're on the path to wizardry, or they're fed Nietzsche (much of Nietzsche's writings, such as The Anti-Christ, were essentially channeled from Satan), and told that SRA is part of being a superman, or part of becoming a superman. They're told whatever it takes to lure them into the trap.
Hellfire Club-style orgies, which are intended to cultivate loveless abandon to one's lowest nature, serve as an entry into Satanism. Their purpose to to elicit possession by proto-humans who currently dwell in Satan's "underworld," and whom I suspect are what "Nietzsche" meant by "supermen." (Note that he considered humans to have no purpose except as a stage in the evolution of "the superman.") The differences between the various types of Satanic possession are beyond the scope of this exposition; suffice it to say that they all instill hostility toward humans.
Tellingly, Mignini did not try to suppress the orgies which reportedly take place in the Perugia area, even though he claimed to believe that they could involve murder. This is because his actual goal was to take murders (apparently committed by organized Satanism), and pin them on innocent people in order to destroy their lives and their minds. He does this by weaving lurid fantasy-versions of "Satanic ritual murder" which involve the murder victim and his (Mignini's) intended victims, and manufacturing evidence to link these fantasies to the real world. Then he and organized Satanism in general attack like piranhas, lying their butts off.
Kercher's killer Guede, I surmise, is also a Satanist. (He seems to enjoy dropping plausibly-deniable hints of this by holding his thumb and index finger extended, and his other fingers curled, thus forming a "666" from a certain perspective.) He probably murdered Kercher at the behest of organized Satanism, and possibly Mignini himself. This would explain Guede's immunity from prosecution for his crime spree leading up to the murder. After all, Mignini (an apparent figurehead for organized Satanism) needed a new murder, and new scapegoats, because his "Monster of Florence"-related "zealous prosecution" had been found to be "mistaken" and had been shut down. The "justice" system slapped him on the wrist for destroying so many lives, wasting vast amounts of time and money, and turning Italy upside down, but it actually did this to protect its image. In fact, the system was set up to serve as a playground for organized Satanism.
Kercher's murder was apparently also partly intended to serve as an advanced form of SRA for Guede, and to give him the impression that it was an initiation into black magic. Although Guede ended up in prison (not even the Italian police could ignore the massive amount of physical evidence against him), his sentence was dramatically reduced, supposedly "due to his age and his clean record." If his record was clean, it was only because the authorities looked the other way while he went on a crime spree leading up to the murder. The real reason is that he's apparently a member of organized Satanism, and of course, to torment Knox and her sympathizers. His lawyer is supposedly still trying to get him declared innocent, and if he actually does, I suppose the Italian government will buy him a luxury crib in some haven for Satanic fugitives from real justice. At least he's no longer homeless, and I haven't been able to find any indication that he is being subjected to SRA in prison, as were Knox, Sollecito, and Lumumba. (Sollecito recently claimed he was subjected to physical abuse during his initial "interrogation.") But Guede, the actual killer, is being treated with kid gloves and with SYMPATHY from the prosecutor!
Mignini is a Satanic monster disguised as a modern-day witch hunter, and he's apparently disappeared from the face of the Earth. But he hasn't given up on tormenting Knox yet, as indicated by the Kerchers' insane "crusade to find the real killers" combined with their threats of suing Knox.