The United States Supreme Court’s understanding of police practices plays a significant role in the development of the constitutional rules that regulate officer conduct. As it approaches the questions of whether to engage in constitutional regulation and what form of regulation to adopt, the Court discusses the environment in which officers act, describes specific police practices, and explains what motivates officers. Yet the majority of the Court’s factual assertions are made entirely without support or citation, raising concerns about whether the Court is acting based on a complete and accurate perception. When it comes to policing facts, the Court too often gets it wrong. This Article explores the influence that the Court’s conception of policing has on the creation and modification of constitutional norms. It demonstrates that misunderstandings about law enforcement have led to constitutional rules that fail to align with the world that they were designed to regulate. Confusion about the facts upon which a rule is built creates a gap between the conceptual justification of the rule and its practical consequences, between the effect that the rule was intended to have and the effect it actually has. Thus, misalignment results in the under- or overregulation of officer behavior and, correspondingly, the under- and overprotection of liberty and privacy interests. This observation offers one explanation for why the Court’s constitutional pronouncements often fail to have the anticipated result. Having identified the effects that follow from basing a rule on a faulty factual premise, I explore ways to narrow the gap. When constitutional rules are predicated on empirical information, a more accurate understanding of police practices will better align those rules with reality, leading to both more precise constitutional rule making and more efficacious liberty protections.