giuliano magnini admitted to us, even without any evidence, he knew almost the moment he arrived and laid eyes on amanda knox and raffaele, they were involved in the murder. >> prior to the forensic investigation, prior to everything really, your intuition or your detective knowledge led you to amanda knox and rafaelle sollecito? >> translator: after the first few weeks we were convinced because of the behavior of the amanda, that they were both involved in a crime. >> reporter: but almost immediately after the arrests, he had a problem. the third suspect, patrick lamumba, had an air tight alibi. he was in his crowded bar that night. he could not have been involved. then the actual forensic tests came back.