He should be something like a cross between the BTK and Zodiac Killers, both known for puzzling the cops with their MO the BTK killer in particular known for calling and taunting the police.
Yeah he liked to taunt the cops but Dennis Rader got caught because he was a fucktard who didn't understand computers.
He actually wrote the cops and asked if floppy disks were traceable. The cops responded (via the papers) "No", so he sent them one with more taunting. Naturally they used the metadata on the disk to track his psycho ass down.
Oddly enough after all he'd done Rader had the nerve to get upset that the cops lied to him.
Hardly a master criminal like The Riddler.