Reporting findings from research on the impact of the Police and Criminal Evidence Act 1984 (PACE), this paper assesses the effectiveness of rights provided for suspects in police custody which were intended to counterbalance increased police powers. It discusses (1) the involvement in the detention and questioning process of parents, social workers, and legal advisers; (2) the procedures which regulate the detention and questioning of suspects before charge; and (3) the effectiveness of sanctions and supervision. It concludes that these safeguards have had a significant, although variable, impact. Factors that have limited this impact are assessed. Claims that suspects’ rights are excessively hampering the detection of crime are criticized.