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Does using a GPS device to track a suspect constitute a Fourth Amendment search?

On November 8th, the Supreme Court will hear oral argument in United States v. Jones, the case on whether installation and/or use of a GPS device on a suspect’s car to record the public places the car travels is a Fourth Amendment search or seizure. I wanted to offer my thoughts on the case, divided into two posts.

At the outset, here’s my bottom line: I’m not sure which side should win. On one hand, I don’t think use of the device should be deemed a search or seizure. On the other hand, I am genuinely divided on whether I think the installation should be deemed a search or seizure. Given these two positions, I don’t have an answer to whether the combined installation and use should be permitted without Fourth Amendment oversight (although I have a lot of views on better or worse ways to get to either result). Regardless of how the Court rules, however, I think a new privacy statute is needed to address both government and private-sector use of GPS surveillance.

On to the first post, on whether use of the device is a search.

I. The Inside/Outside Distinction

Let’s start with first principles. The text of the Fourth Amendment states that the Amendment protects security in “persons, houses, papers, and effects,” and the Fourth Amendment’s prohibition on unreasonable “searches” does so by protecting invasions into those private spaces. Over the years, the Supreme Court has developed a relatively simple line for distinguishing the invasions into persons, houses, papers, and effects that the Fourth Amendment regulates as “searches” from the investigative steps that the Fourth Amendment does not regulate. That distinction is the line between what I will call inside surveillance and outside surveillance: Surveillance of outside spaces is always permitted, while surveillance of inside spaces is a regulated “search.”

Consider a few examples. Government entry into a home is a search, as is entry into a car, or a sealed package, or a letter, or a person’s pockets. These are all intrusions into persons, houses, papers, and effects. They are all searches. On the other hand, surveillance in public places that does not enter into private spaces, such as watching someone on the street, looking at their faces, examining the outside of their packages, overhearing their voice, or following someone in a store open to the public, is not a search. These are not intrusions into persons, houses papers, or effects, and they are not searches under the Fourth Amendment.

Interestingly, you get these same results regardless of which version of the Supreme Court’s doctrine you apply. You get the same results whether you get these results under the “protected areas” test that preceded the 1967 Katz case, or the Katz “reasonable expectation of privacy” test that the Court has adopted since then. The results are the same: A search occurs when the government intrudes upon a private person, house, paper, or effect, but does not occur when the government merely observes something in a public space or in a space where the government is otherwise entitled to be. I will refer to this using the short-hand of inside versus outside surveillance, as I did in this article.

The fundamental distinction between inside and outside surveillance leads to some close calls, to be sure. For example, imagine the police approach a home, walk directly up to an open window, press their faces up to the window, and peer in to see what is in the room inside. Technically, that is surveillance from an open space, but functionally it is surveillance of the inside of the home. Is that protected inside surveillance, or unprotected outside surveillance? The Supreme Court has created the distinction between “curtilage” and “open fields” to answer that: The outside area immediately around the home that can be used to peer inside the home is treated as inside surveillance (curtilage) rather than outside surveillance (open fields). See United States v. Dunn. Similarly, imagine the police use a thermal imaging device to determine the exterior temperature of a wall on the home. Is that outside surveillance, as it is only of the outside of the wall exposed to the public, or is that inside surveillance, as it reveals information about the inside of home? It’s a tricky call, as the 5-4 decision in Kyllo v. United States reveals. But the basic point remains: The distinction between inside and outside surveillance is the basic building block of the Supreme Court’s “search” cases.

II. The Knotts and Karo Precedents from the Radio Beeper Era

How does this distinction apply to the use of government surveillance devices installed to determine the location of property used or controlled by a criminal suspect? The Supreme Court first grappled with this in two cases in the 1980s, United States v. Knotts and United States v. Karo. Both cases involved radio beepers provided by the government that the suspects did not realize were present and broadcasting their location. The technology was crude compared to today’s GPS technology, but it did the job: It enabled the government to know the location of the beepers, and thus, implicitly, the location of the suspects that the police wanted to follow.

Knotts and Karo reasoned that the way to translate the traditional Fourth Amendment protection to the era of high-tech radio beepers was to focus on the information that the surveillance devices revealed. Recall that the traditional Fourth Amendment rule was that the police could always watch a suspect in public (no search), but that they could not enter protected spaces without a warrant or some Fourth Amendment oversight (a search). Knotts and Karo together drew the same line for government-installed location devices: If the device is used to monitor a location in public, then no search occurred (Knotts), but if the device was used to monitor a location inside a protected space, like a home, then a search occurred (Karo).

To my mind, there is a lot of wisdom in the Knotts/Karo line. As I argue in a forthcoming article, it is a constant challenge for courts to adjust Fourth Amendment rules to maintain the level of constitutional protection as technology changes. I think Karo and Knotts did that quite well: They maintained the basic distinction between inside and outside surveillance by focusing on whether the information obtained was information about what was happening outside (the location of property out in public) or what was happening inside (the location of property inside a home). The facts changed, but the Knotts/Karo line maintained the same equilibrium of police power and privacy rights across that shift from one technology (visual surveillance) to another (radio beepers).

III. Does GPS Surveillance Justify A Departure from the Knotts/Karo Line?

That brings us to Jones. In Jones, a GPS device was placed on the suspect’s car. The trial court concluded that the evidence of the GPS device in the suspect’s garage had to be suppressed under Karo, but that the evidence of the GPS device in public was permitted under Knotts. Only the latter evidence, the evidence of the location of the car on the public street, is at issue in the Jones case. The basic argument of the defendant-respondent in Jones is that GPS surveillance is different from radio beeper surveillance, and that those differences justify a departure from the Knotts/Karo information-based approach. The gist of the argument is that GPS monitoring is just too invasive to be allowed without judicial oversight — the monitoring is too constant, too easily done, too continuous, and too detailed.

As I understand this argument, the basic move is to replace the inside/outside distinction with a different approach, one based on a more amorphous standard of what is very invasive. According to the respondent in Jones, the Fourth Amendment should not track inside versus outside: Rather, it should measure an overall amount of invasiveness. Under that approach, a person can have a reasonable expectation of privacy in open public spaces just as they can in private spaces. What matters is whether the manner in which the public or private surveillance is conducted is too invasive and creepy to go without Fourth Amendment protection, not whether the monitoring happens to be of public and open or private and enclosed spaces.

I think this is an unpersuasive argument, and that the Justices should reject it for three reasons.

First, the inside/outside distinction is too deeply rooted in text, history, and precedent for the Court to depart from it lightly. It’s such a cornerstone of the law that the Justices should not cast it aside without a good reason. Second, as I have argued in detail elsewhere, the inside/outside distinction serves an important function — one that would be maintained by retaining that distinction as technology changes:

The line between inside and outside also serves an essential function for Fourth Amendment law. The inside/outside distinction exposes to government observation some basic information about what people did and where they went while simultaneously shielding their most personal information from police scrutiny absent cause. This is true because individuals do not usually leave their personal or sensitive belongings out in the open. Instead, they hide them from view by putting them inside in an enclosed space. The inside/outside distinction therefore reveals where people are and where they are going while shielding their most private thoughts and speech from government view.

This division in turn ensures a basic balance of Fourth Amendment protection. If the Fourth Amendment protected everything, then the police would have great difficulty solving crimes; even walking down the street with eyes open would require probable cause. On the other hand, if the Fourth Amendment protected nothing, we would be inadequately protected against abusive government invasions of our homes and private spaces. The inside/outside distinction strikes one of several possible middle grounds. The police can watch a person out in public, but ordinarily they cannot enter the kinds of private spaces where individuals typically hide their more sensitive belongings.

Third, and of most interest here, rejecting the outside/inside distinction requires devising a new distinction. This proves surprisingly hard. Some line must be drawn, and rejecting the inside/outside distinction means that some new way of drawing the Fourth Amendment line must be created. (It is no answer to say that the “reasonable expectation of privacy” test provides that new way, as this is backwards; we’re debating how the “reasonable expectation of privacy” test should be applied, so saying that the test should apply doesn’t tell us anything.) Once you cast aside the inside/outside line, what replaces it? The respondent and amici briefs in Jones offer no persuasive answer to this question, for reasons I’ll get to in the next section.

IV. What Could Replace the Inside/Outside Distinction?

For the most part, the briefs for Jones (both parties and amici) don’t dwell on this question. They contend that the facts of this case are on the other side of the line from those of Knotts, but they never disclose what the line is. The GPS monitoring here is more invasive than the radio beeper in Knotts, the argument runs; It was more continuous, and cheaper, and was more detailed, and it occurred for longer. As a result, the government ended up with more information and there is a greater risk of abuse. On the facts, that is true. But I don’t see the the precise point at which Knotts turns into Jones under these efforts to distinguish the two cases. The briefs just argue that the line has been crossed somehow, at some point. Even the proponents of the argument can’t seem to identify with any specificity when that happened.

Some of the pro-Jones briefs suggest that identifying the precise line is unnecessary. Courts adopt vague standards all the time, the argument runs, so they can do so here. But I think that argument ignores the reality of modern criminal investigations. State, local, and federal agencies employ 870,000 law enforcement officers in the United States today. When those officers investigate cases, they often go right up to the line that the Constitution allows. If the Court announces to 870,000 officers that the radio beeper of Knotts is not a search, but the GPS device used in Jones was, many officers are going to push and prod and go just as far as they can to determine at exactly what point the Knotts territory runs out.

That’s a serious concern given that the programmable nature of location devices such as GPS devices. The GPS device in Jones recorded location every 10 seconds whenever the car was in motion. But that’s not an inherent feature of GPS devices; It’s just what this particular device was programmed to do. If the Court concludes that using a GPS set to record for 10-second intervals for a month is too long, how about a 1-hour interval for 20 days? How about a 20-minute interval for 10 days, then 5 days off, and then a 5-hour interval for 10 more days? How about filtering the location data so it is somewhat less precise, or a lot less precise, or only gives a very rough location of the device? The officers can program the GPS any way they like. If the Court rejects the inside/outside distinction and tries to adopt some generalized invasiveness approach, officers will just program the frequency, duration, and precision of their GPS devices so they fall just a hair short of the Jones line. I think that makes the need for a clear line particularly pressing, and the absence of such a line in the pro-Jones briefs particularly telling.

V. Conclusion

That brings me back to the Knotts/Karo line. For the reasons I explained earlier, I think the Knotts/Karo line provides a sensible way to translate the inside/outside distinction from the context of physical entry into spaces to the context of location devices. Given the absence of a feasible alternative — and the possibility of statutory regulation and constitutional regulation of the installation of the device, which I’ll address in my next post — I think the Court should stick with that line and conclude that use of the GPS device to record location of a car in public is not a Fourth Amendment search.

(cross posted, with some modification, at The Volokh Conspiracy)

Recommended Citation: Orin Kerr, Does using a GPS device to track a suspect constitute a Fourth Amendment search?, SCOTUSblog (Oct. 21, 2011, 3:09 PM),