Watching through this it's interesting that Howard keeps getting minor details wrong, and the guy will continually correct him on minor details from earlier in the story.

Robin will ask Clay a question but Howard will answer it but incorrect in some way and he'll correct him. Then they'll get into one of these sidetracks and then will address Clay again with another incorrect statement (He said the woman he killed was 16) and the dude corrected him again after some time had passed.

I'm guessing it's intentional on Howard and Robin's. It doesn't feel staged it feels too mundane, and radio stations all the time would get calls by people claiming they were serial killers so I'm sure they had some sort of protocol that would happen before they could even get to air. Plus I would think they'd get in some serious trouble if they staged this call themselves.

Howard also cuts him off when the guy tries to get into more lascivious details, he'll immediately put him on the defensive about what makes him so angry and then try and glean more information from him. It's interesting to see how he's literally verbally sparring with the guy getting him to open up and then hitting him with a jab when he does.