This book examines how legal and policy actors negotiate the demands of controlling crime and respecting individual rights against a background of uncertain scientific knowledge. Bringing together insights from criminology, psychiatry, psychology, and law, it unpicks competing images of ‘dangerous’ offenders and the dilemmas they present. It does so by tracing the creation of a new group—‘dangerous people with severe personality disorders’—by policymakers in England and Wales in 1999—and by situating contemporary debates about ‘dangerous’ offenders within a historical context. Through a critique of sentencing law, mental health law, and human rights law, this book further examines an alluring narrative: that the state has a duty to protect the public from ‘dangerous’ individuals, but that it can protect the human rights of the ‘dangerous’ by providing them with rehabilitation opportunities. While human rights law is often invoked as a means of curbing the excesses of preventive justice, this book demonstrates that the European Court of Human Rights tends to legitimize coercive measures. Furthermore, the criminal law legitimizes the punishment of offenders with mental disorders by resisting psychiatric evidence that they are not fully responsible for their actions. But the law also has the resources to tackle these seemingly intractable dilemmas, and this book therefore puts forward modest reform proposals.