What Makes an Expectation of Privacy “Reasonable”? A Response to Chief Justice Roberts

During the oral argument a few weeks ago in United States v. Jones, Chief Justice Roberts had some very interesting questions about the Fourth Amendment’s “reasonable expectation of privacy” test. I fear that the Chief Justice’s questions may reflect a common misunderstanding of the test. In this post, I wanted to explain the Chief’s possible error, and explain how I think the reasonable expectation of privacy test is supposed to work.

I. The Possible Misunderstanding

The questions that grabbed my attention seemed to assume that the “reasonable expectation of privacy” test asks an empirical question — that a Fourth Amendment expectation of privacy is “reasonable” when reasonable people expect privacy. Just before the relevant exchange, Deputy SG Michael Dreeben had argued that using a GPS device on the suspect’s car could not have infringed the suspect’s reasonable expectation of privacy because it only revealed the suspect’s location in public. The Chief Justice responded:

CHIEF JUSTICE ROBERTS: I give you that, that it’s in public. Does the reasonable expectation of privacy trump that fact? In other words, if we ask people, do you think it’s — it violates your right to privacy to have this kind of information acquired, and everybody says yes, is it a response that, no, that takes place in public, or it simply the reasonable expectation of privacy regardless of the fact that it takes place in public?

MR. DREEBEN: Well, something that takes place in public isn’t inherently off limits to a reasonable expectation of privacy. That’s essentially the holding of Katz. You go into a phone booth, you’re in a public; making your calls within the phone booth is subject to a reasonable expectation of privacy. But this Court, with full awareness of that holding, in Knotts and in Karo recognized that surveillance of a vehicle traveling on the public roadways doesn’t fit that description.

CHIEF JUSTICE ROBERTS: You can see, though, can’t you, that 30 years ago if you asked people does it violate your privacy to be followed by a beeper, the police following you, you might get one answer, while today if you ask people does it violate your right to privacy to know that the police can have a record of every movement you made in the past month, they might see that differently?

A similar point came up later in the same argument when counsel for Jones argued that “society does not expect” monitoring like GPS monitoring and therefore it violates a reasonable expectation of privacy. Chief Justice Roberts responded by asking how we know what people think is a violation of privacy:

CHIEF JUSTICE ROBERTS: How do we tell? I mean, I don’t know what society expects. I suppose if you ask people do you think it’s a violation of privacy for the police to do this for no reason for a month, maybe they would come out one way. If you asked the people do you think the police have to have probable cause before they monitor for 5 minutes the movements of somebody they think is going to set off a huge bomb, maybe you get a different answer.

Interestingly, Chief Justice Roberts had a similar line of questioning during the April 2010 oral argument in City of Ontario v. Quon, which raised a question (that the Court ultimately did not answer) of whether people have a reasonable expectation of privacy in text messages. Quon was a police officer who had been given a text pager by the city; he had been told that he could use the pager for personal messages but that the city would audit the messages and that he had to pay for any overage charges caused by his personal messaging. The city ultimately did audit the messages, read them, and use them to embarrass Quon, and Quon claimed that this violated his Fourth Amendment rights. Chief Justice Roberts’ questioning again went to what privacy a reasonable person might expect:

CHIEF JUSTICE ROBERTS: Well, we are dealing with Mr. Quon’s reasonable expectations, right?

MR. RICHLAND: Yes, yes.

CHIEF JUSTICE ROBERTS: And even with the written policy, he has the instructions — everybody agrees — you can use this pager for private communications.

MR. RICHLAND: That’s correct.

CHIEF JUSTICE ROBERTS: We’re not going to audit them. Right? That’s what he said. He has to pay for them. Right? Now, most things, if you’re paying for them, they’re yours. And this — it particularly covered messages off-duty. Now, can’t you sort of put all those together and say that it would be reasonable for him to assume that private messages were his business?

It’s important not to make too much of questions at oral argument, of course. Sometimes oral argument questions are designed to play devil’s advocate, or to point out problems to other Justices. But my sense from both arguments is that Chief Justice Roberts may understand the “reasonable expectation of privacy” test to pose an empirical question: The Court determines when an expectation of privacy is “reasonable” by asking whether a reasonable person would expect a privacy right in those circumstances.

I think this understanding is incorrect, although I come across it often: Indeed, I have encountered it sufficiently often that I have responded to it here before. But given that the issue keeps coming up, I wanted to explain a bit more why I don’t think it’s correct.

II. What Makes an Expectation of Privacy Reasonable?

The trick to understanding this problem is that the phrase “reasonable expectation of privacy” is a legal term of art that shouldn’t be applied literally. As the Court explained in United States v. Jacobsen, “[t]he concept of an interest in privacy that society is prepared to recognize as reasonable is, by its very nature, critically different from the mere expectation, however well justified, that certain facts will not come to the attention of the authorities.” Put another way ,a reasonable expectation of privacy is not the same as the expectation of privacy of a reasonable person. This point is clearer and less counterintuitive if we use the alternative articulation of the Katz test. The Court uses “reasonable expectation of privacy” and “legitimate expectation of privacy” interchangeably, but I think the latter term is less confusing and more revealing about what the test is and how it should be applied.

So if an expectation of privacy isn’t reasonable (or “legitimate”) when a reasonable person would have that expectation, when is it reasonable (or “legitimate”)? I think the most helpful explanation in the caselaw was authored by then-Justice Rehnquist in Rakas v. Illinois:

Obviously, however, a “legitimate” expectation of privacy. by definition. means more than a subjective expectation of not being discovered. A burglar plying his trade in a summer cabin during the off season may have a thoroughly justified subjective expectation of privacy, but it is not one which the law recognizes as “legitimate.” His presence, in the words of Jones, 362 U.S. at 362 U. S. 267, is “wrongful”; his expectation is not “one that society is prepared to recognize as reasonable.'” Katz v. United States, 389 U.S. at 389 U. S. 361 (Harlan, J., concurring). And it would, of course, be merely tautological to fall back on the notion that those expectations of privacy which are legitimate depend primarily on cases deciding exclusionary rule issues in criminal cases. Legitimation of expectations of privacy by law must have a source outside of the Fourth Amendment, either by reference to concepts of real or personal property law or to understandings that are recognized and permitted by society. One of the main rights attaching to property is the right to exclude others, see W. Blackstone, Commentaries, Book 2, ch. 1, and one who owns or lawfully possesses or controls property will, in all likelihood, have a legitimate expectation of privacy by virtue of this right to exclude.

Expectations of privacy protected by the Fourth Amendment, of course, need not be based on a common law interest in real or personal property, or on the invasion of such an interest. These ideas were rejected both in Jones, supra, and Katz, supra. But, by focusing on legitimate expectations of privacy in Fourth Amendment jurisprudence, the Court has not altogether abandoned use of property concepts in determining the presence or absence of the privacy interests protected by that Amendment. No better demonstration of this proposition exists than the decision in Alderman v. United States, 394 U. S. 165 (1969), where the Court held that an individual’s property interest in his own home was so great as to allow him to object to electronic surveillance of conversations emanating from his home, even though he himself was not a party to the conversations. On the other hand, even a property interest in premises may not be sufficient to establish a legitimate expectation of privacy with respect to particular items located on the premises or activity conducted thereon. See Katz, supra at 389 U. S. 351; Lewis v. United States, 385 U. S. 206, 385 U. S. 210 (1966); United States v. Lee, 274 U. S. 559, 274 U. S. 563 (1927); Hester v. United States, 265 U. S. 57, 265 U. S. 58-59 (1924).

Rehnquist sharpens the analysis significantly in this passage, I think. He points out that the test isn’t about empirical expectations; that it’s not just a circular question; that it has to be rooted in some outside source; and that no one outside source is dispositive. Further, Rehnquist starts off the list of possible outside sources that can make an expectation of privacy reasonable: property is one, and “understandings that are recognized and permitted by society,” whatever that may mean, is another.

Back in 2006-07, I wrote an article that went through all of the Court’s “expectation of privacy” cases and developed a comprehensive list for what sources the Court has relied on: I called the article “Four Models of Fourth Amendment Protection,” as I found four different kinds of arguments (what I called “models”) that the Court has used to justify expectations of privacy. More broadly, that article tried to explain why the Court has used the different explanations, and why no one explanation suffices: The test for what is a search has to distinguish less invasive types of law enforcement steps from more invasive types of steps, all in a world in which the facts of investigations are constantly changing and new facts are arising, and no one test seems to do that in a way that can be readily administered in a complex court system.

Of course, that doesn’t mean that reliance on the four models is ideal, although as I explain in the article, I do think it has a lot of unrecognized benefits. And as I have explained more recently, it does facilitate the needed equilibrium-adjustment in cases that involve new technologies. But at a minimum, I think this does explain why the Court does not and should not apply the “reasonable expectation of privacy” test simply by asking when a reasonable person would expect privacy.