Television-serial serial-killers typically have high IQs. It's the part of the conceit that keeps the character from getting caught, so they can keep making ne

Television-serial serial-killers typically have high IQs. It's the part of the conceit that keeps the character from getting caught, so they can keep making new episodes. They're smart enough to stay one step ahead of the law, but the chief investigator is also smart, so the killer can never get more than two steps ahead. The possibility of getting caught out from just one misstep keeps the tension in the show. Real serial killers are average intelligence, chased by cops with average intelligence. They get caught for the same reasons that get other criminals collared. They get sloppy, and they fall into predictable patterns, or the cops get lucky. The only reason they can commit the same crime multiple times is that real investigative police work is difficult without CSI-style magical technology. Most people could formulate a simple set of rules that would keep their crimes separate from their public identity--until one of them hits a corner case and leaks critical information. Don't burgle houses with dogs. Always burn the clothes you wore. Never look inside the package. Use encryption and dead drops. Put thermite on incriminating storage devices. Never work the same postal code twice. Don't work with a pimp. Always pay the boss exactly what you owe. Don't surface the submarine until you get within 50m of the floating dock. Wives and kids are off limits. Don't spend your share conspicuously. Don't sample the goods. Don't talk about Project Mayhem. &c. &c. &c. It doesn't require mastermind-level plotting. The hardest part about crime is finding a person willing to do it. A lack of empathy goes a long way towards that, and an unwillingness to take responsibility for the consequences of one's actions gets even closer. The smart criminals don't murder people; instead they go into real-estate fraud, money laundering, and insider trading. The money is better and the prosecutions rarer.