My recollection is that the murderer there isn't really convinced he committed a perfect crime but frequently is panicked and pushed to extremes by suspicion th

My recollection is that the murderer there isn't really convinced he committed a perfect crime but frequently is panicked and pushed to extremes by suspicion that he's being toyed with (and in particular, the detective was intentionally making him ride a roller coaster of more or less suspicion of this)?