Aviello has multiple charges of calunnia:
http://www.repubblica.it/cronaca/2011/05/21/news/omicidio_meredith-16566127/
http://www.umbria24.it/meredith-aviello-%C2%ABho-detto-cose-false-concordate-con-gli-avvocati-di-sollecito-in-cambio-di-soldi%C2%BB/52791.html
This is your own theory. And this, with all due respect, is only your opinion, which you are free to have.
You can quote case-law, but you are not really bringing a foundation for the interpretation of ECHR principles on the basis of your legal doctrine.
In fact between me and you there is an apparent a clash between legal doctrines. I maintain that you doctrine is unfounded and unreasonable. I maintain it is false under the principles or ECHR. It is not that that you don't cite cases, it's that your categorization of them is wrong.
On the other hand, whilt the ECHR does not have a specific precedent for calunnia, the Italian Cassazione does specifically address the calunnia with reference to the concept of "right of a suspect to defend himself", stating that the calunnia is not an action "covered" by the guarantees, rights and protections of the defendant (or suspect) which include a right to remain silent.
There are - by the way - also other kinds statements that would be "not covered" thus punishable as crimes themselves even if released within a police interrogation, for example: revealing classified information or military secrets, declaring false ID info, presenting a false document number, providing false information as a police informant. Those are crimes. If you commit them, you can hardly invoke the protection of the ECHR stating that they didn't let you talk with your lawyer first.
You place the calunnia within the set of the "statements", while I place calunnia among the "crimes", not covered by the clause of protection of suspect's rights.
This - if it was a serious matter - would be a clash between legal doctrine. Your 'doctrine' maximixes one specific right, acknowledged by ECHR, and makes it become absolute. You do not just apply it to the activity of releasing statements that fall within the rights of a defendant or suspect, you extend it to any statement.
But in fact, your doctrine is unreasonable; rights and principles are not absolute, they limited by the existence of other conflicting rights and principles.
Beyondf this there is also a point of common sense, not just about rights but also about likeliness and opportunity:
Amanda Knox fingered the "village black man", she accused someone who was obviously innocent, multiple times, declining the accusation in multiple ways (interrogation, statement, written memorials with insinuations against multiple people, refusal to declare) while she carved an innocent role for herself. This is not something that typically an innocent person would do.
Anna Donnino testified that Amanda Knox made a statement, not that the police prepared one. Anna Donnino was a reliable witness. Then Amanda Knox wrote further false accusations and held a prolonged deceitful conduct. And judges found that Knox's statements were malicious.
You are making up everything here. There is no "failure" to provide anything, and there is nothing "indicative". But there is a testimony by Anna Donnino, and witnesses are credible.