Fourth Amendment law is sorely in need of reform. To paraphrase Justice Sotomayor’s concurrence in United States v. Jones, the idea that people have no expectation of privacy in information voluntarily shared with third-parties—the foundation of the widely reviled “third-party doctrine”—makes little sense in the digital age.

In truth, however, it is not just the third-party doctrine that needs retooling today. It is the Fourth Amendment’s general approach to the problem of “shared information.” Under existing law, if A shares information with B, A runs the risk of “misplaced trust”—the risk that B will disclose the information to law enforcement. Although the misplaced trust rule makes sense as a default, it comes under strain in cases where A and B have no relationship of trust and the only reason that A shares information with B is to obtain a socially valuable (and practically indispensable) service. In such cases, I argue that the doctrine should treat B as an “information fiduciary” and analyze B’s cooperation with law enforcement—whether voluntary or compelled—as a Fourth Amendment search.

The argument develops in three parts. Part I demonstrates that the Court has already identified two settings—if only implicitly—where fiduciary-style protections are necessary to safeguard constitutional privacy: medical care and hotels. When A is a patient and B is a doctor, and, likewise, when A is a guest and B is a hotel manager, the Court has been reluctant to apply the “misplaced trust” rule. Rightly so: the principle is mismatched to the underlying relationship. From there, Part II fleshes out the normative argument. Put simply, we do not “trust” information fiduciaries, in the everyday sense, at all. So it makes little sense—normatively, or even semantically—to speak of trust being “misplaced.” Rather, the information is held for the benefit of the sharing party, and its use should be constrained by implied duties of care and loyalty. Finally, Part III lays the groundwork for determining who are “Fourth Amendment fiduciaries.” The Article concludes by exploring various practical metrics that courts might adopt to answer this question.