Chapter 14 - Forensic Psychiatry, Substance Use and Mental Illness

Abstract

This chapter focuses on the relationship between substance abuse and addiction, and competence to stand trial and affirmative defenses. Psychoactive substances (substances) are chemicals that affect the way an individual feels, thinks, behaves, and functions on an interpersonal and social level. Alcohol, illicit drugs, and certain prescribed drugs can produce acute intoxication or withdrawal, and lead to substance abuse or addiction (dependence). An affirmative defense is a plea to justify that an act was at least legally permissible, such as self-defense, or an excuse that admits the act was wrong but argues that the defendant should not be blamed for it in such situations as duress, insanity, automatism, entrapment, or necessity. In general, the law across the United States to date has prohibited the use of insanity defenses by addict defendants facing serious criminal charges. This stance is, however, at odds with the prevailing view of the medical and mental health community in the United States, which has largely recognized that addiction is, in fact, a mental illness. Competency to stand trial is probably the most common evaluation done by psychiatrists for the court system. The Supreme Court defines competency to stand trial as the ability of a defendant to have a rational and factual understanding of the proceedings against him or her, and to assist and consult with an attorney with a reasonable degree of rational understanding.