It's one of the most common assumptions in true crime, but the answer is more complicated than most people realise. In this episode of UNMARKED: Case Notes, I speak with Dr. Louis Schlesinger, Professor of Psychology at John Jay College of Criminal Justice and one of the world's leading experts on serial and sexual homicide. 

If you've ever wondered whether psychopathy is required for serial murder, or why some killers appear cold and calculating while others seem disorganised, impulsive, or deeply disturbed, this conversation is for you.