>V2
I'm no psychologist / psychiatrist but I could only hazard to guess that the murderer / fetishist can compartmentalize one action from another such that to him how he acts in 'normal life' is quite separate, indeed maybe even a separate person from his evil life & thus he can't allow in his mind a collision between the two to occur. The interview part I saw to me was him realizing that the collision was about to occur and he was trying to find a way to keep them apart. The detective was showing him the way to keep them apart was to admit what had happened.
To 'normal' people obviously the things are not separate at all but once the guy is satisfied that admission satisfies his own fears he then makes the admission.
It's very disturbing to watch it but fascinating.