Utilitarian notions of public expedience and the public good have been used to justify the use of 'supergrasses' in Northern Ireland despite misgivings that self-confessed criminals go free or are given lenient penalties. In Northern Ireland, the majority of 'supergrasses' have been recruited during interrogation after arrest or sentencing. The types of people who have been recruited -- ruthless terrorists, the mentally unstable, and the weak-willed -- raise concerns about the strategy. 'Supergrass' inducements include money, a new job or identity, and immunity from prosecution. The 'supergrass' strategy represents a fundamental shift in policy by radically extending the role of the criminal law. The use of 'supergrass' evidence creates a climate of fear and distrust among terrorists and raises the possibility of innocent people being named by a self-confessed criminal who has everything to gain. Comparisons between the use of 'supergrasses' in England and Italy are not valid. In Northern Ireland terrorists have considerable public support; the proportions of the population engaged directly or indirectly in the violence are much greater; and the authorities lack adequate support and popular legitimacy. Although 'supergrass' strategy may not have been as successful as the authorities have claimed in reducing violence or putting terrorists out of action, it does provide counterintelligence. A total of 73 notes and references are listed.