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?

The authors argue persuasively that U.S. law is out of touch with the way that jurors' "commonsense justice" works and the way they judge culpability. This disconnect has resulted in some inconsistent verdicts across different types of cases and thus has serious implications for whether the law will be respected and obeyed.

Problems arise because criminal law has no unified theory of emotion and culpability, and legal scholars often seem to misunderstand or ignore what psychologists know about emotion. The authors skillfully show that the law's culpability theories are (and must be) psychological at heart, and they propose ways in which psychology can help inform and support the law.