Reasonable Expectations of Privacy and Novel Search Technologies: An Economic Approach

The “reasonable expectation of privacy” test, which defines the scope of constitutional protection from governmental privacy intrusions in both the United States and Canada, is notoriously indeterminate. This indeterminacy stems in large measure from the tendency of judges to think of privacy in non-instrumentalist terms. This “moral” approach to privacy is normatively questionable, and it does a poor job of identifying the circumstances in which privacy should prevail over countervailing interests, such as the deterrence of crime. In this paper, I develop an alternative, economically-informed approach to the reasonable expectation of privacy test. In contrast to the moral approach, which treats privacy as a fundamental right, the economic approach views it as a (normatively neutral) aspect of self-interest: the desire to conceal and control potentially damaging personal information. On this view, privacy should not be protected when its primary effect is to impede the optimal deterrence of crime. Legal protections against governmental surveillance, however, may in other cases enhance social welfare by encouraging productive transactions, diminishing the costs of non-legal privacy barriers, and limiting suboptimal policing practices, including discriminatory profiling and the enforcement of inefficient criminal prohibitions. Economics and public choice theory can also help to minimize decision-making error by predicting which legal actors – police, legislatures, or courts – are best placed to make optimal trade-offs between privacy and crime control. I first describe the United States and Canadian supreme courts’ reasonable expectation of privacy jurisprudence and canvass its chief inadequacy: the vagueness of the “public exposure” and “intimacy” doctrines that the courts have used to decide whether to regulate novel search technologies. I then outline the economic approach to the reasonable expectation of privacy test. Next, I apply this approach to two technologically advanced search tools: infrared imaging and location tracking. This analysis suggests that courts should recognize a reasonable expectation of privacy in the latter case, but not the former