At the risk of repetition, it may be useful to emphasize one issue that some may find confusing.
When the ECHR uses the terms "suspect" or "accused" it defines those terms "autonomously" - that is, using it own meaning, which goes beyond the "formal" definition which may be used in a state's legal system.
First, a brief review of the relevant Italian law and the way it was apparently applied to Amanda Knox.
In the Italian legal system, according to the Italian Code of Criminal Procedure (Codice di Procedura Penale, CPP), a person becomes a formal suspect when a prosecutor records that person's name as a suspect in a crime in the log book reserved for such records. However, the CPP also recognizes that a person under questioning may be or become a suspect without such a recording.
CPP Article 63 provides, in a first case, that a person questioned as a witness happens to make an incriminating statement, that person becomes a suspect because of that statement as soon as that statement is uttered. Thus, according to that law, the questioning must be stopped, the person must be informed that investigations may be launched against him and that he is advised of his right to get a lawyer. His incriminating statement (which was made without a lawyer or the legally required warnings, including among others of his right to remain silent) may not be used against him, according to that law.
CPP Article 63 also provides, in a second case, for the possibility that the person being questioned as a witness should actually have been considered a suspect (but was not formally a suspect) from the beginning of questioning and, therefore, should have been questioned as a suspect: that is, in the presence of a lawyer and with the legally required warnings. In this case, if the person questioned makes an incriminating statement, the same actions must be taken by the authorities conducting the questioning as in the first case. However, in this second case, no statement from the questioning may be used against the person question nor any other person.
In the Knox case, the Gemelli CSC panel applied this CPP Article 63 to her 6 November 2007 interrogation statements, for the charges of murder and rape. Thus, the 1:45 am statement could not be used against Knox, and the 5:45 am statement could not be used against Knox or anyone else.
However, for the criminal charge of calunnia, the Gemelli CSC panel apparently allowed both of Knox's statements to be used against her. Gemelli did not (as far as I can tell) cite the jurisprudence (case-law) of the CSC regarding this decision, but rather invoked Memoriale 1, as a defensive document written by Knox of her own volition after the questioning, as bringing her interrogation statements into play. The Italian government, however, in its responses to the ECHR, apparently only invoked the general jurisprudence of the CSC as justifying the use of Knox's statement against her for the criminal charge of calunnia.
Now for the ECHR's definition of "suspect" based on its case-law. It is this definition which must be considered as applicable to all states of the Council of Europe, including Italy.
110. The protections afforded by Article 6 §§ 1 and 3 apply to a person subject to a “criminal charge”, within the autonomous Convention meaning of that term. A “criminal charge” exists from the moment that an individual is officially notified by the competent authority of an allegation that he has committed a criminal offence, or from the point at which his situation has been substantially affected by actions taken by the authorities as a result of a suspicion against him (see Deweer v. Belgium, 27 February 1980, §§ 42-46, Series A no. 35; Eckle v. Germany, 15 July 1982, § 73, Series A no. 51; McFarlane v. Ireland [GC], no. 31333/06, § 143, 10 September 2010; and, more recently, Ibrahim and Others v. the United Kingdom [GC], nos. 50541/08 and 3 others, § 249, ECHR 2016).
111. Thus, for example, a person arrested on suspicion of having committed a criminal offence (see, among other authorities, Heaney and McGuinness v. Ireland, no. 34720/97, § 42, ECHR 2000‑XII, and Brusco v. France, no. 1466/07, §§ 47-50, 14 October 2010), a suspect questioned about his involvement in acts constituting a criminal offence (see Aleksandr Zaichenko v. Russia, no. 39660/02, §§ 41-43, 18 February 2010; Yankov and Others v. Bulgaria, no. 4570/05, § 23, 23 September 2010; and Ibrahim and Others, cited above, § 296) and a person who has been formally charged, under a procedure set out in domestic law, with a criminal offence (see, among many other authorities, Pélissier and Sassi v. France [GC], no. 25444/94, § 66, ECHR 1999‑II, and Pedersen and Baadsgaard v. Denmark [GC], no. 49017/99, § 44, ECHR 2004‑XI) can all be regarded as being “charged with a criminal offence” and claim the protection of Article 6 of the Convention. It is the actual occurrence of the first of the aforementioned events, regardless of their {recorded?} chronological order, which triggers the application of Article 6 in its criminal aspect.
Source: SIMEONOVI v. BULGARIA [GC] 21980/04 12/05/2017
37. The Court .... recalls in this regard its consistent jurisprudence that the concepts of "criminal charge", "accused of an offense" or "accused" in paragraphs 1, 2 and 3 of Article 6 of the Convention must be 'to be understood as having an 'autonomous' scope in the context of the Convention, and not on the basis of their meaning in domestic law (Adolf, cited above, § 30, Simeonovi v. Bulgaria [GC], No. 21980/04, §§ 110-111, May 12, 2017). The prominent place that the right to a fair trial occupies in a democratic society argues for a "material" rather than "formal" conception of the "accusation" governed by Article 6 of the Convention; it directs the Court to look beyond appearances and to analyze the realities of the proceedings at issue as to whether there was an "accusation" for the purposes of Article 6 of the Convention (Adolf, cited above, ibid.).
Source: STIRMANOV v. RUSSIA 31816/08 29/01/2019
(Translated from the French by Google with my help.)
Thus, for Knox v. Italy, the ECHR "raises the question" but does not explicitly rule whether Knox was already a suspect (by its definition) at the beginning of the 5/6 November 2007 interrogations. On the other hand, it points out that Knox was certainly a suspect following her first (1:45 am) statement, that is during the interrogation session that produced the 5:45 am statement. In this last ruling, the Chamber judgment conservatively avoids a thorough investigation of the circumstances of the first interrogation while maintaining agreement with the Gemelli CSC panel judgment. However, the ECHR case-law does not allow the use of a statement made without a lawyer to serve as the sole evidence in a criminal conviction, even when the alleged crime is the statement itself.
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