Much is written about how criminal suspects, defendants, and undercover targets use ambiguous language in their interactions with police, prosecutors, and undercover agents. This book examines the other side of the coin, describing fifteen criminal investigations demonstrating how police, prosecutors, undercover agents, and complainants use deceptive ambiguity with their subjects, which leads to misrepresentations of the speech events, schemas, agendas, speech acts, lexicon, and grammar. These misrepresentations affect the perceptions of judges and juries about the subjects’ motives, predispositions, intentions, and voluntariness. Deception is commonly considered intentional while ambiguity is often excused as unintentional performance errors. Although perhaps overreliance on Grice’s maxim of sincerity leads some to believe this, interactions of suspects, defendants, and targets with representatives of law are adversarial, non-cooperative events that enable participants to ignore or violate the cooperative principle. One effective way the government does this is to use ambiguity deceptively. Later listeners to the recordings of such conversations may not recognize this ambiguity and react in ways that the subjects may not have intended. Deceptive ambiguity is clearly intentional in undercover operations and the case examples illustrate that the practice also is alive and well in police interviews and prosecutorial questioning. The book concludes with a summary of how the deceptive ambiguity used by representatives of the government affected the perception of the subjects’ predisposition, intentionality and voluntariness, followed by a comparison of the relative frequency of deceptive ambiguity used by the government in its representations of speech events, schemas, agendas, speech acts, lexicon, and grammar.