No, you are right, Hellman does not cite the specific evidential basis for his findings but it cannot be inferred that those findings are not grounded in evidence. Where else, aside from the defence expert, can he have got all that stuff about her mental state? After setting it all out, he says:
However, this Court does not find that there is any significant objective evidence that, when she made her spontaneous statements and wrote her note, Amanda Knox was in not only a situation of considerable psychological pressure and stress but also even in a condition of not intending or wishing; so that, having accused of such a serious crime a person whom she knew to be innocent, she must in any case be held responsible for the crime of calumny, the constitution of which does not require any specific purpose from a psychological point of view, such as shifting the blame off of oneself [conseguire la propria impunità] (an aggravating circumstance alleged [here]). Generic criminal intent [il dolo generico] is sufficient, thus including the aim of escaping from a particularly oppressive personal situation.
I am guessing questions about her mental capacity were put to her expert and that he was not able to go so far as to say she lacked the ability to form criminal intent. We need a transcript of his evidence.
Another take on your highlighted clause. Hellmann is subtly referring to any violation of CPP Articles 188 and 64 para. 2. He's saying that even if the police violated these laws, Amanda Knox must be responsible for her speech under their interrogation (and immediately afterwards). These procedural laws prohibit altering the "moral freedom" of self-determination of a person. IMO, the highlighted statement by Hellmann is a clear reference to this alteration of a person's self-determination, in which the person is made to say something against his or her own wishes or intent. Also to be noted, in CPP Art. 64, para. 3, the warnings not given to Amanda during her questioning. In CPP Art. 64, para. 3-bis, it is disclosed that statements made under questioning may not be used if the witness is not warned. Thus, if the Italians obeyed their own laws, but acknowledged that they had failed to give these warnings, since Amanda was not warned, the statement she allegedly gave naming Lumumba could not itself be used against Lumumba!
CPP Article 188 Moral freedom of the person during evidence gathering
1. Methods or techniques which may influence the freedom of self-determination or alter the capacity to recall and evaluate facts shall not be used, not even with the consent of the person concerned.
CPP Article 64 General rules for questioning
2. {Same text as Article 188}
3. Prior to the questioning, the person must be warned that:
a) his statements can always be used against him;
b) {except for identification information} he has the right to silence, but the proceedings will in any case continue their course;
c) if he makes any statement on facts concerning the liability of others, he will become a witness in relation to those facts {unless the other is a co-accused}.
3-bis. If the provisions of para. 3 (a) and (b) are not fulfilled, the statements made by the person questioned shall be excluded. If the person questioned is not warned according to para. 3 (c), the statements that he may have made on the facts regarding the liability of others shall not be used against them, and he shall not become a witness in relation to those specific facts.