And Frank's article said the killer escaped to England!
Personally I think it was not a good idea to have these convicts testify, but if they absolutely had to why did they not just drop Aviello? He completely contradicted the story of the other convicts so far as to even claim Rudy was also innocent. That only looked bad IMO and took away from any credibility any one of them may have garnered on the stand.
Because you (and many others) still don't seem to be able to grasp the situation properly. The defence's claim was this: there are two groups of people - a group of 4 (including Alessi), and Aviello - who have made potentially significant claims regarding this case. Neither the defence, nor the prosecutors, nor the police, nor the courts have any real idea just how accurate, truthful or reliable either of these claims is, mainly because the police and prosecutors declined to investigate properly when they first came to light, and because Judge Massei arbitrarily refused to let the claims be investigated in the first trial.
Therefore, the defence demanded that these claims were investigated in open court so that everybody could determine their veracity. The defence are not asserting that either or both of these groups of people are telling the truth - and nor have they ever made this assertion. Their view is that either one might be true, or both might be false, but until and unless the claims were subjected to official court scrutiny, it would be near-impossible to investigate them properly (i.e. courts have powers of investigation and subpoena that defence lawyers (or even prosecutors) don't have).
This request was all about allowing the claims to be properly investigated. What it emphatically was
not was the defence claiming that one or both of these claims was necessarily forming part of its defence against the murder charges. Obviously, if either of the claims turns out to have any substance, then the defence will likely use that information to its benefit. But if both claims turn out to be lies, then the defence will be satisfied that they were investigated properly and found to have no substance, and move on accordingly.
At the risk of repeating myself
ad nauseum, the is NOT the adversarial (prosecution vs defence) anglo-saxon justice system, where each side only produces witnesses who support that side's case. The Italian courts retain elements of an inquisitorial approach, and also have an investigative role to play in and of themselves. I wish people were able to understand the differences, and to therefore appreciate the real reason why the defence wanted these inmate witnesses heard and examined in court.