Taken together, the Supreme Court of Canada’s recent judgments in R. v. Hart and R. v. Mack represent a coherent approach to confessions arising from Mr. Big operations. The Court has now recognized that these operations carry risks of generating evidence that is both unreliable and prejudicial, and of becoming abusive. Hart and Mack erect some safeguards for the accused in the Mr. Big context. The judgments should encourage police to exercise restraint in using the technique and courts to be more vigilant in assessing the resulting confessions. Even outside the Mr. Big context, the judgments may be relied on in future cases to place some limits on undercover operations. Finally, it is argued that the Court’s approach to the reliability problems of Mr. Big confessions carries the potential to enhance protections against wrongful convictions based on other forms of unreliable evidence. Hart can be read as recognizing trial judges’ discretion to exclude unreliable evidence, while Hart and Mack together suggest that both an exclusionary rule and a rule requiring cautionary jury instructions may be needed to respond to serious concerns about the reliability of prosecution evidence.