This book examines the role of civil law in determining mental capacity over a five hundred year period in England and in New Jersey.The influence of civil law on the history of madness has not hitherto been of major academic investigation. This body of law, established and developed over a five hundred year period, greatly influenced how those from England's propertied classes understood and responded to madness. Moreover, the civil law governing the response to madness in England was successfully exported into several of its colonies, including New Jersey. Drawing on a well-preserved and rare collection of trials in lunacy in New Jersey, this book reveals the important ties of civil law, local custom and perceptions of madness in transatlantic perspectives. This book will be highly relevant to scholars interested in law, medicine, psychiatry and madness studies, as well as contemporary issues in mental capacity and guardianship.