My claim is falsifiable and if it was shown to be wrong I would concede the point.
The factual aspects yes; but the 'fact' that something is unethical is not easily falsifiable.
Please find an example where testimony in the form of a letter was allowed to be read at a trial when the author of the letter was allowed to invoke his right against self incrimination to prevent his cross examination unless an obvious exception to the right to cross examine witnesses applies such as the death of the author.
But you guys are incredible. I don't know cases by memory (and this is not a common law system). What I wonder is why the decisions by Hellmann-Zanetti court and the Supreme Court are not enough for you to understand the procedure point.
Asking about cases about prosecution reading a letter is far beyond what should be necessary to understand: the right of a witness like Rudy Guede to remain silent is expressed by the code, art. 197-bis.
And while we are on the subject of Guede's refusal to submit to a cross examination because it would have tended to incriminate him: Huh? Did the judge interrogate him as to how his testimony might lead to self incrimination? The right not to testify because of the possibility that it might lead to self incrimination is not some sort of rule that can be invoked at the prosecutor's discretion. There is supposed to be a legitimate possibility of self incrimination. How could Guede incriminate himself for a crime that he had been convicted of and was essentially confessing to in the letter read at the trial?
But this is wrong; it seems like you are projecting the US fifth-emendment on the Italian law. But it's not the same. That the right to not answer by a witness in Italian law is
not directly related to possibility of self-incrimination like in the US law. I'd say it's very different in some aspects.
I would say the faculty of not answering in Italian procedure law is more 'difficult' for the witness/suspect to have it granted compared to the US, but it is much more powerful and extensive once the required status is achieved by the person.
In Italy, the faculty belongs only to formal suspects, defendants or convicted, while there is no protection from self-incrimination for simple witnesses. And it is very extensive, it includes a right to chose which questions not to answer, a right to lie, a right to make any kind of statements in every moment.
Now, the right to remain silent is not limited to topics which may lead to self-incrimination. It extends up to all topics for which the person cannot be obligated answer: note that we are talkinge about the right to remain silent of a witness, who has however achieved also the status of "defendant" in something connected. But as the status of defendant ends with the verdict, his right to remain silent about facts for which he was convicted is achieved permanently. He will keep the right to remain silent about those facts for his whole life.
He is not protected because of danger of self-incrimination. He is protected because of art. 194-bis paragraph 4. Nobody can obligate him to tell anything different from what he told as a defendant, nor to say anything about the topic for which he was convicted. Never. And forever.