Your point about overlooking confessions is unrelated to what I implied. Most of us get tired in the wee hours of the night and are less able to think coherently.
Dr. Giobbi testified that he was mathematically sure he said to bring them both in. In addition, Raffaele's book notes that a policeperson put the name of a lawyer into his hand before the 5th. And (as Malkmus unearthed a long time ago IIRC) there was a report in an Italian media outlet on the 5th that started out "Ominous Words" and went on to say that it was not unlikely that a witness would become a suspect in the next few hours.(snip)
And I would add to that, from Burleigh's book:
Erika Pontini, who covered the case in Perugia for La Nazione of Florence and who was close to Officer Napoleoni, recalled, On the night of the fifth, we knew, journalists knew, something was going to happen. They thought Sollecito was the fragile link in the chain.