This book investigates why, when, and how ordinary human beings hold some individuals guilty of crimes, but others less so or not at all. Why, for example, do the emotions of the accused sometimes aggravate a murder, making it a heinous crime, whereas other emotions might mitigate that murder to manslaughter, excuse a killing ("by reason of insanity"), or even justify it ("by reason of self-defense")? And what emotions on the part of jurors come into play as they arrive at their decisions?