Abstract

Ideas of prevention (the prevention of harms, or of wrongs, or of crimes) have always played a significant role in accounts of the proper aims of a system of criminal law, but in recent years they have come to play a more prominent and disturbing part in developments in criminal law policies—most obviously, but by no means only, in the USA and Britain. Governments have sought to meet (or to be seen to be meeting) a range of perceived threats, such as terrorism, organised crime, and various kinds of sexual predation, by looking for more effective modes of prevention. Sometimes this involves expanding the criminal law to capture more types of preparatory conduct, or conduct (including various kinds of possession) that might facilitate the commission of target crimes; sometimes it involves expanding non-criminal provisions for preventive detention, or other kinds of restriction on the liberty of those thought to be dangerous (restrictions that may themselves be backed by criminal sanctio