The Yale Law Journal

May 2019

The Voluntariness of Voluntary Consent: Consent Searches and the Psychology of Compliance

Criminal ProcedureConstitutional Law

abstract. Consent-based searches are by far the most ubiquitous form of search undertaken by police. A key legal inquiry in these cases is whether consent was granted voluntarily. This Essay suggests that fact finders’ assessments of voluntariness are likely to be impaired by a systematic bias in social perception. Fact finders are likely to underappreciate the degree to which suspects feel pressure to comply with police officers’ requests to perform searches.

In two preregistered laboratory studies, we approached a total of 209 participants (“Experiencers”) with a highly intrusive request: to unlock their password-protected smartphones and hand them over to an experimenter to search through while they waited in another room. A separate 194 participants (“Forecasters”) were brought into the lab and asked whether a reasonable person would agree to the same request if hypothetically approached by the same researcher. Both groups then reported how free they felt, or would feel, to refuse the request.

Study 1 found that whereas most Forecasters believed a reasonable person would refuse the experimenter’s request, most Experiencers—100 out of 103 people—promptly unlocked their phones and handed them over. Moreover, Experiencers reported feeling significantly less free to refuse than did Forecasters contemplating the same situation hypothetically.

Study 2 tested an intervention modeled after a commonly proposed reform of consent searches, in which the experimenter explicitly advises participants that they have the right to withhold consent. We found that this advisory did not significantly reduce compliance rates or make Experiencers feel more free to say no. At the same time, the gap between Experiencers and Forecasters remained significant.

These findings suggest that decision makers judging the voluntariness of consent consistently underestimate the pressure to comply with intrusive requests. This is problematic because it indicates that a key justification for suspicionless consent searches—that they are voluntary—relies on an assessment that is subject to bias. The results thus provide support to critics who would like to see consent searches banned or curtailed, as they have been in several states.

The results also suggest that a popular reform proposal—requiring police to advise citizens of their right to refuse consent—may have little effect. This corroborates previous observational studies that find negligible effects of Miranda warnings on confession rates among interrogees, and little change in rates of consent once police start notifying motorists of their right to refuse vehicle searches. We suggest that these warnings are ineffective because they fail to address the psychology of compliance. The reason people comply with police, we contend, is social, not informational. The social demands of police-citizen interactions persist even when people are informed of their rights. It is time to abandon the myth that notifying people of their rights makes them feel empowered to exercise those rights.

authors. Roseanna Sommers is a Harry A. Bigelow Teaching Fellow and Lecturer in Law, University of Chicago Law School. Email: Vanessa Bohns is an Associate Professor of Organizational Behavior, Cornell University ILR School. The authors wish to thank Ian Ayres, John Bargh, Paul Bloom, Adam Chilton, Andrew Crespo, Barry Friedman, Orin Kerr, Marianne LaFrance, Benjamin Levin, Tracey Maclin, Jonathan Masur, Richard McAdams, Janice Nadler, John Rappaport, Carol Steiker, Kate Stith, Lior Strahilevitz, Tom Tyler, Leaf Van Boven, Tess Wilkinson-Ryan, Gideon Yaffe, Crystal Yang, Jonathan Zittrain, and the editors at the Yale Law Journal. Ava Barnett, Kelly Jahnsen, David Navadeh, and Harry Trabue provided invaluable research assistance. This research is supported by NSF Grant #1823661, the Oscar M. Ruebhausen Fund, and the Wachtell, Lipton, Rosen & Katz Program in Behavioral Law, Finance and Economics.

The original dataset used in this Article is available at It is also preserved in eYLS, Yale Law School’s data repository, at