<i>Katz</i>'s Imperfect Circle: An Empirical Study of Reasonable Expectations of Privacy

Under Katz v. United States, the Fourth Amendment restricts government actions that infringe upon expectations of privacy that society recognizes as reasonable. This foundational test has long been criticized as circular, both because courts can shape the very expectations they seek to identify through their decisions and because governments can manipulate those expectations to expand the reach of their own power. But how do members of society decide what expectations are reasonable, and how do judges ascertain those expectations? And are expectations of privacy malleable even without deliberate manipulation? This Article shows that the circularity critique is both understated and overstated. We identify six different potential elements of Katzian circularity, some of which have never been examined—particularly those relating to the stickiness of precedent concerning changing technology. To test the import of these circularity elements, we conducted two empirical studies, one survey and one experiment. We found that individuals’ beliefs about whether expectations of privacy are reasonable are highly influenced by data about what others think. Telling a person that a majority (versus a minority) of people believe a privacy right exists significantly increases their belief in that right to privacy. We also found evidence that people tend to view the investigative uses of new technologies as particularly violative of privacy expectations. Yet, we found little evidence beliefs are influenced by legal precedent or government action—with one important exception. It seems court decisions do not commonly shape society’s expectations, nor do they reflect society’s expectations. The larger problem is that judges are likely to conflate society’s expectations with their own expectations. We show how turning the reasonable expectation of privacy inquiry into one hinging on scientifically-based research, rather than on judges’ unsound intuitions, would better fulfill Katz’s mandate and reflect societal consensus on these most fundamental constitutional principles. Altogether, this Article comprehensively charts the theoretical possibilities of Katzian circularity, empirically shows why and how the problem is likely to arise, and supplies a solution.