Okay, mostly, I've been fascinated about them from an early age because they are at both complex and shallow at the same time. They can be a source of infinite evil, especially the ones who grew up in perfectly normal households, and then became Jeffrey Dahmer, or Ted Bundy-ish. A lot of them are broken, but a large block of them are just evil sons of bitches who need to be put down like the rabid dogs they are.
Because no, to understand all is not necessarily to forgive all. Sometimes it just makes it easier to find and kill the little bastards.
Nowadays, the only way to catch a serial killer is to get lucky. Any similarities between real serial killers and Criminal Minds is ... usually in the footnotes of the early episodes, where they told you what serial killer they were stealing from that week.
There's a lot of police work, there's a lot of forensics, and you have to have teams of cops continually drilling down on the manhunt until someone gets lucky. Or good. Usually both. Because the problems of catching serial killers is usually a matter trying together a connection between victims killed (most likely) by a total stranger. In a world where most people are killed in the middle of the night, in their own bedroom, by their nearest and dearest, murder by stranger is a great way to get away with it. Strangers on a Train works for a reason.
When I was designing Codename: UnSub, it was simple: how do you catch a serial killer, trained to be a professional assassin, in a city where half the population is psychotic, and there are no cops?
And then, to up the ante, I made certain that one of the victims has the power to end the world,
But, hey, no pressure.
One of the reasons I wanted to have this be a murder mystery is that mysteries have always been a snapshot of culture, and cultural assumptions. When Sherlock Holmes assumes that a man is a bachelor by a frayed button on a sleeve, it's a bit of a snapshot of 19th century Victorian London.
For Codename: UnSub, I decided that this nightmare San Francisco needed more personality, and more depth. I was going to spell out some of the sects and factions. Because in order to find one killer in a city of killers, Kevin Anderson is going to have to dig through plenty of insanity.
Obviously, I'm not going to get anywhere near as deranged as real life serial killers. There will be none of the Ted Bundy "strangled while being raped" victims. There will be no Dahmer cannibalism or pederasty. There will definitely be no Ed Gein "ashtrays made from human skin." There will be no "stab a victim in the gut and then have penile penetration of the wound."
We're just not going to go there.
There are sadistic murderers, there are sexual sadists. There are hunters who like the stalking of victims and do little about the kill. There are some who really like to take their time.
Though don't worry, if you want something gruesome, I can manage that. I've got a killer who basically likes to beat people to death. And fight them until they fall down. Then drag them to their feet and simply continue breaking things. And then, when they can't stand anymore, continue to break every last bone in the victim's body.
So, hopefully, serial killer fans will not be disappointed in just how much of a sick son of a bitch we have in this one.