Automatism is a notoriously difficult subject for law students, lawyers, and judges. This book explores the science and medicine of sleep disorders and examines how the criminal process deals with such disorders when presented as a defence. It lays out systematically, logically, and simply the legal doctrines and their implications for the use of expert evidence which is key to establishing automatism. It also looks at the medical conditions that can cause automatism and the expert evidence that will support a defence of automatism – in particular epilepsy, sleepwalking, and diabetes. Comparisons are drawn across a range of common and civil law jurisdictions. The book provides a useful expansion on the content of standard legal textbooks thus enabling a fuller understanding of the automatism defence. As such it will be a valuable resource for law students, lawyers, judges, and expert witnesses.