The discrepancy that has long fascinated me is randomness. In mysteries, the murder is always intentional. There may be a red herring body thrown in, someone killed by accident or design to throw off the sleuths, but ultimately, the murderer has a motive. An actual, definable reason why Miss Scarlet wants Mr. Boddy dead. That can be a real struggle for the crime fiction writer, because for all the variations on a theme, all credible motives boil down to Love and Money. (There used to be a third motivator, Shame and Reputation, but that died the day the Jerry Springer Show went on the air.)
But in studying real crime, one of the first thing that strikes you is the randomness of it. Someone was walking down the wrong street. Stopped at this red light instead of that one. Spilled a drink on a guy at the bar. There was a woman who was killed in nearby Scarborough, Maine by two drifters. They took $20 off her body and her 10-year-old minivan. When they were caught, they said they just picked the first person who came out of the supermarket where they were panhandling.
The idea that one could be a victim for no other reason than walking out of the Shop 'n Save is terrifying. And I suspect it's why both crime fiction and true crime writers focus on elaborate schemes involving spurned lovers or disputed inheritances. The reader gets a great deal of satisfaction, not just from following the thread of clues through the labyrinth, but also from the thought that it couldn't happen to me. I didn't marry a con man, I didn't embezzle from my boss, I didn't hang around with gangsters at nightclubs. It couldn't happen to me.
I became particularly fascinated by the role of randomness in crime after reading Judgment Ridge: the True Story of the Dartmouth Murders by Dick Lehr and Mitchell Zuckoff. In January 2001, Half and Susanne Zantop were found slashed to death in their Etna, New Hampshire home. The two were long married, popular professors at Dartmouth, with no obvious enemies or looming financial difficulties. The deaths shocked and horrified northern New England and became one of the largest investigations ever undertaken by the NHSP Major Crimes Unit.
I won't spoil the investigation for you—the book is well worth reading for it's depiction of the careful, meticulous policing that broke the case—but the murderers are a matter of public record: two teenage boys with knives and an almost unbelievable disconnection with reality. They picked the Zantops to rob and kill because there was no dog barking at the couple's isolated house.
Judgment Ridge directly influenced one of my own books. I wanted to see exactly how close to that terrifyingly random killing I could get and still meet the genre expectations of mystery. (I won't tell you which one it is. If you've read it, you'll know.) I still find myself flirting with that edge, and I wonder, do mystery readers always need a motive for murder? Or are they ready for truly realistic crime in their novels? After all, there's no reason given for Col. Mustard or Mrs. White to commit murder, They were there. The lead pipe was there. That was enough.