During the course of my investigations as a forensic psychiatrist, I have profiled and/or interviewed more than eighty serial killers. When I speak to them or to members of their families, it is always my policy to have each of them sign a legal release form that allows me to use what they tell me for scientific purposes. Some of the letters and interviews from the people I have profiled appear in this book. They’re presented here not for the purpose of titillation but to help the reader understand the theories that I put forth in this book.