In preparation for NaNoWriMo 2010, I read a book called The Evil That Men Do by Stephen Michaud, a study of serial rapists and killers, written in collaboration with Roy Hazelwood, a pioneer in FBI profiling. I knew that, even as she was gifted (read: cursed) with the ability to fight evil, my main character was also going to become a powerful magnet for evil. And it seemed logical that, since she was a cute young woman with a job that involved working in a semi-seedy neighbourhood, often late at night, she would become a magnet for the type of men Hazelwood spent his career profiling.
One of the things I found most fascinating about this book was the fact that until relatively recently, sex crimes like rape were almost impossible to analyze, because nobody wanted to do it. When Hazelwood started his career, anyone who was interested in trying to understand the motivations behind such crimes were considered perverts, especially by fellow law enforcement officers. So the intimate interrelationship between sex criminals and killers went long unacknowledged. And yet, many serial killers begin their careers as rapists. What begins as a desire to dominate women (and, more rarely, men) often culminates in the desire to take a life.
Hazelwood was unique in his day in noticing that not all rapists and killers are alike. He made important key distinctions between chaotic, spur-of-the-moment, opportunistic serial murderers, and those who were meticulous planners.
The discipline of serial killer profiling opened up a whole new world (or maybe dark underbelly) to writers. Killers are useful in our fiction, and may even be the focal character. Jeff Lindsay's Dexter series of books depends on playing the line between the cultural fascination with killers and fantasies of vigilante justice.