But in fact, Mignini never proposed any 'ritualistic' nor any 'Halloween-sect-like' scenario for the Meredith murder. There may be well erroneous sources; but none of these sources was in the courtroom, because the trial was hold behind closed doors; and in fact all these sources are British newspapers that seem to be relying on (as they interpret it) a source at La Repubblica, a journalist who himself explicitly states that he is reporting second-hand comments from Il Giornale dell'Umbria.
But when you look at the trial transcripts, there is nothing alike.
As for the Narducci case, I don't know first-hand because I never read the documents, but I never heard about a Satanic scenario involving that.
There has been a discussion about satanic scenarios during the MoF trials in Florence, because there were witnesses who brought that in and also in the investigation elments were found suggesting links with with Satanism, they are in the records but they plaid no role in the trials so far.
But I point out that the MoF case is not the Narducci case; Mignini had nothing to do with the MoF investigation and trials.
There was some element linking to Satanism that enetered also the Narduci case, because the Narducci case resulted from the merging of more than one case; the merge was requested by Florence, it was not Mignini's idea. One of the three original investigations (later merged into one) was a case of anonimous phone stalking against a woman in Perugia, which went on for years, by unknown people who called from telephone boxes in Tuscany mentioning Narducci's 'murder' together with 'sexual' and 'satanic' themes. Apart from this, which was obviously an original theme 'intrinsic' to the case, there has never been any 'satanic' scenario in the Narducci investigation.
A 'ritualistic' or sect-like scenario - albeit never formally proposed - is instead something much closer to what investigators hypothesized in the end. The MoF murders apparently were committed with the purpose of collecting fetishes, and such fetishes may have had some ritual or 'magical' use.