There is an interesting nuance to this, in February 2011 Kaosium posted
The Italian System is different in that it is a three tier procedure, or four to five in a sense. There's the initial 'Court of Freedom' or somesuch which determines if they have enough evidence to prosecute, then an initial trial, then an appeal trial de novo which means it's basically another whole trial unlike in our systems, then it goes to the Supreme Court where it must be ratified to ensure it's in total compliance with the law.
Assuming this is correct, with the annulment of Hellmann,
Nencini should have conducted an appeal trial de novo, since the initial appeal trial de novo ceased to exist, as the guilters like to emphasise.
So the question for them is do they regard Nencini as another whole trial? Maybe Machiavelli will help here.
An appeal is what we call an appeal, not a trial de novo.
However, an appeal it is not the same thing what the US system calls an "appeal"; that is more like something an Italian would call a "review".
The Hellmann verdict ceased to exist almost entirely, but the court hearings and documentation from the Hellmann appeal are part of the proceedings.
An appeal is different from a trial de novo, in that: 1) it usually incorporates the evidence and papers from the previous stage, and decides "on the papers"; 2) it starts from the presumption that rationale for the decisions from the lower courts on decisive elements were correct (needs to argument against previous findings and decisions if comes to different conclusions); 3) it starts from a presumption that evidence admitted was complete (needs to argument if decides to re-open a phase of evidence discussion on certain topics).
The Supreme Court does not only provide for "compliance with the law", but, so it puts it itself, also provides for "a standardization of interpretation of law and evidence". The word "Cassazione" means, more or less "destruction", from the verb "cassare", shred into pieces and throw away (destroys the judge's decisions that finds to be "sub-standard").
The initial courts are not called "Court of Freedom" (a Court of Freedom actually exists, but deals only with custody measures of detainees), they are called Preliminary Investigation Judges (the Investigating Judge, and the Preliminary Judge).
The Preliminary Judge can also decide on the verdict, if the defendants asks him so (it's called abbreviated trial). If this happens, the judges decides "on the papers", without admitting further evidence hearing sessions besides those agreed with the prosecution. The defandant can also ask for abbreviated trial under the condition that he/she could present some specific defensive evidence or call some defence witness.
There is also a "review" judge which operates subsequenty to the Investigating Judge in the investigation stage when suspects are hold under cautionary measure (reviews the conclusions of the Investigating Judge).
The Preliminary Judge accesses the files from the Investigating Judge hearings and may access the police interrogation files.
The Court may not access the the files from the preliminary stages instead (they are inadmissible).
Decisions of courts do become definitive even if not signed off by the Cassazione, if they are not appealed to the Cassazione after a scheduled period of time (usually about 45 days).