Abstract: The mid-twentieth century witnessed a boom in policing against homosexual cruising, the practitioners of which relied on a set of robust defense tactics to avoid detection by strangers. Frustrated by the difficulties of catching suspected cruisers, police departments developed a variety of surreptitious, deeply intrusive surveillance tactics for monitoring public bathrooms. Yet while necessitated by the insularity of modern cruising culture, these surveillance tactics were legitimized in court partly through judges’ very skepticism of that culture. Weighing the utility of clandestine surveillance against its intrusion on innocent citizens, judges frequently justified surveillance by characterizing cruisers as sexual predators eager to expose themselves to innocent victims. From inception to conviction, the utility of clandestine surveillance thus depended partly on an epistemic lag between the arms of the criminal justice system: a disconnect between the police’s sensitivity to contemporary homosexual practices and judges’ continuing insistence on an older paradigm of perverse predation.