One day, well into the future, I'll write historical fiction. In fact, I already have some story ideas in mind, but the research and writing for the first book will take a good four-year stretch. Plus, I'm in no hurry to begin such ambitious work tomorrow. I have the Cameron Ballack series to finish, which means I'm living in the murder mystery world for a few more years.
All of which means a specific way of writing a novel. Crime fiction requires many things. You need a well-crafted story. You need to sit down and think through the array of characters, their own fictitious backgrounds. You need to plot out the flow, chapter-by-chapter--in some cases scene by scene and line by line. If part of a series, there are issues of flashback, foreshadowing, and things arcing from previous events into the present moment. But there's one aspect of writing crime fiction that has come more front and center than I ever dreamed: the construction of a believable villain.
Crime fiction requires a criminal. The murder mystery, a more focused subset of crime fiction, requires someone even more evil than a garden-variety criminal. You have to create someone cloaked in literary obfuscation until revealing him (or her) as the murderer. You have to hide the fact they are guilty but make the revelation of their actions make sense when disclosed to the reader.
A literary murderer--like onions and ogres--has layers...layers than can be developed in many ways. But one way I've tried to make it work in my stories is having the murderer reach out to me. Yes, you read that right. I write myself a letter to myself from the perspective of the murderer, detailing their background, their motives, their reasons, their excuses, their anger, their rage, and their pain. The letter gets quite personal and edgy, the more the better I think. The goal is to bring about a person who is calculating and strategic. Someone whom the reader might sympathize with, be ambivalent about, or dislike...it doesn't matter. But I want the "why" of the murder firmly fixed in the heart of the criminal. The more definitively I can lodge it deep in the killer's soul, the better character I have.
All of which is to say this is one way to pull this off. It may not work for everyone. And it might not be the best way to build a murderous character. When Litany of Secrets finally comes out this year, we'll see how productive a path it is. But I do find it to be a fun challenge, and as a writer you can't ask for much more than that.