Kind of sickening how he builds up his ego and tells him he loves him. Seems like that kind of treatment could potentially skew the accuracy of the confession. “Hmm, I like being loved and praised and fed milkshakes here in prison, I’m going to keep talking, even if it isn’t true!”
Maybe sometimes it's better to get very unreliable information and try to confirm it independently, the classic example being if they say something only the killer would know like where the body is buried.