In the first half of the 1980s a series of high profile and deeply controversial trials, some larger than any criminal proceedings hitherto seen in Ireland or the UK, took place in Northern Ireland on the evidence of "supergrasses" prepared to betray large numbers of their alleged accomplices in return for various rewards. This major scholarly study, which for the first time discusses supergrass trials in a broad criminological, historical, legal, and comparative context, will make a timely and enduring contribution to debates about security policy and anti-terrorist law enforcement in Northern Ireland and the rest of the United Kingdom.