This study traces the transition of treason from a personal crime against the monarch to a modern crime against the impersonal state. It consists of four highly detailed case studies of major state treason trials in England beginning with that of Thomas Wentworth, first Earl of Strafford, in the spring of 1641 and ending with that of Charles Stuart, King of England, in January 1649. The book examines how these trials constituted practical contexts in which ideas of statehood and public authority legitimated courses of political action that might ordinarily be considered unlawful - or at least not within the compass of the foundational statute of Edward III. The ensuing narrative reveals how the events of the 1640s in England challenged existing conceptions of treason as a personal crime against the king, his family and his servants, and pushed the ascendant parliamentarian faction towards embracing an impersonal conception of the state that perceived public authority as completely independent of any individual or group.