Book excerpt: Whether the accused is competent to stand trial, whether the plaintiff is competent to accuse, or whether a witness is competent to testify has had a long legal history. Such questions draw legal reasoning into areas of ethical reflection and scientific debate deeply rooted in the moral history of the United States. Mental competence has come to play a central and controversial role in proving guilt, and in evaluating the severity of a crime and its corresponding punishment. This compendium brings together the major legal precedents and legal commentaries that have defined the role of mental illness in criminal trials throughout U.S. history. The reprint collection considers, among other issues, the evolution of the Supreme Court's position on the insanity defense and mental retardation, how these affect one's competency to stand trial or be executed, and how these affect culpability and punishment. Each volume begins with an introductory essay, and includes both cases and commentary. Scholars as well as students will find these volumes a useful research tool.