The American criminal justice system is based on the bedrock principles of fairness and justice for all. In striving to ensure that all criminal defendants are treated equally under the law, it endeavors to handle like-cases in like-fashion, adhering to the proposition that the same rules and procedures should be employed regardless of a defendant’s wealth or poverty, social status, race, ethnicity, or gender. Yet, exceptions have been recognized when special circumstances are perceived to have driven a defendant’s behavior or are likely to skew the defendant’s trial. Examples include the right to act in self-defense and to be appointed an attorney if you cannot afford one. Another set of exceptions, but ones that are much more controversial, poorly articulated, and inconsistently applied, involves criminal defendants with a mental disorder. Some of these individuals are perceived to be less culpable, as well as less capable of exercising the rights all defendants retain within the justice system, more in need of mental health services than criminal prosecution, and warranting enhanced protections at trial. As a result, special rules and procedures have evolved over the centuries, often without fanfare and even today with little systematic examination, to be applied to cases involving defendants with a mental disorder. This book offers that systematic examination. It identifies the various stages of criminal justice proceedings when the mental status of a criminal defendant may be relevant, associated legal and policy issues, the history and evolution of these issues, how they are currently resolved, and how forensic mental health assessments are conducted and employed during criminal proceedings.