I am listening to it now. DW seems to perceive that they don't believe him, but sounds honest and straightforward. He acts like he just wants to help the police, get this over with, and get home. What a naive sucker. They (police) probably kept going out of the room to keep from laughing. The more he talked (or anyone for that matter) the more they had to try and trip him up.
Whether you believe it or not, I can get you and two 'interviewers' in a room, and can end up having you in tears and totally broken. The key is usually that the accused thinks that if they keep talking, they will give police that one answer that will satisfy them, and allow them to go home. The police are using little tricks right now (as I am listening) to keep DW talking, without really telling him he can't go. The big trick is the "well, Dave, you are lying and if you can't prove otherwise, we got ya". "Now, you can go home, we won't arrest you".
He trusted them. He was more naive than people that believe that the police don't arrest you if you are innocent.