It's interesting," he says. "I've worked on cases where burglars have crapped in the house - and I always ask the police whether it's soft or hard. They look at me like I'm absolutely mad. And I say, if it's soft, then it's somebody who's anxious, so you get a kid who goes and craps on the bed. And if it's really hard stool then it's an indication of somebody who's angry and bitter about what he's doing."