The GPS Device: Law Enforcement’s Dirty Little Secret?

This Sunday, the New York Times reported on a recent trend–prosecutors’ growing use of a defendant’s Global Positioning System device (e.g., cell phone, car, among others) to prove the defendant’s location. For instance, prosecutors in suburban Chicago used data from a defendant’s GPS device in his car to place the defendant at the scene of a murder. To be sure, tracking a person’s location is common-place in criminal investigations. But my colleague Renée Hutchins (who is quoted in the NY Times article) cautions that law enforcement should be allowed to acquire GPS data only by getting a warrant. In her recent UCLA Law Review article entitled Tied Up in Knotts? GPS Technology and the Fourth Amendment, Hutchins develops that argument.

Here is the Article’s abstract:

Judicial and scholarly assessment of emerging technology seems poised to drive the Fourth Amendment down one of three paths. The first would simply relegate the amendment to a footnote in history books by limiting its reach to harms that the framers specifically envisioned. A modified version of this first approach would dispense with expansive constitutional notions of privacy and replace them with legislative fixes. A third path offers the amendment continued vitality but requires the U.S. Supreme Court to overhaul its Fourth Amendment analysis. Fortunately, a fourth alternative is available to cabin emerging technologies within the existing doctrinal framework. Analysis of satellite-based tracking illustrates this last approach.

The Global Positioning System (GPS) allows law enforcement officials to monitor an individual’s precise movements for weeks or months at a time. GPS technology not only is substantially different than anything the Court has previously considered, but also is a substantial threat to fundamental notions of privacy. By illustrating how, with only minor tweaking, existing Fourth Amendment law can effectively rein in intrusive applications of this one emerging technology, this Article begins to construct an analytical framework that can be applied more broadly to future technological enhancements.

This Article begins by reviewing the science and capabilities of GPS-enhanced surveillance. It concludes that satellite-based tracking is a powerful investigative tool that enables authorities to monitor the movements (both indoors and out) of an unlimited number of people for weeks or months at a time. This Article then examines the Court’s historical treatment of technologically enhanced surveillance, and shows that the intrusiveness of an emerging technology is critical to its constitutional treatment. Considering the intrusiveness of GPS-enhanced tracking, this Article concludes that the unfettered use of such surveillance is inimical to fundamental Fourth Amendment principles. The most defensible treatment of GPS tracking under the existing analytical framework is that it is a search and, as such, must be preauthorized by a warrant issued only upon probable cause.

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9 Responses

  1. Orin Kerr says:

    Considering the intrusiveness of GPS-enhanced tracking, this Article concludes that the unfettered use of such surveillance is inimical to fundamental Fourth Amendment principles. The most defensible treatment of GPS tracking under the existing analytical framework is that it is a search and, as such, must be preauthorized by a warrant issued only upon probable cause.

    Isn’t this another way of saying that Knotts was wrongly decided? I think it’s really pretty hard to square that doctrinal outcome with existing law and Knotts in particular.

  2. Renee Hutchins says:

    “Isn’t this another way of saying that Knotts was wrongly decided?” I don’t think so. It would certainly be easier to make the case that GPS tracking deserves warrant protection if we were writing on a blank slate. But, even operating with Knotts as a precedent, I think you can tease out enough to justify a warrant requirement for GPS tracking devices. Knotts reaffirms the Court’s presumptive treatment of sensory-enhancing v. extra-sensory devices. So, it begins with the presumption that devices that merely mimic human sensory perception are non-searches. Because the beeper in Knotts did little more (according to the Court) than mimic an officer’s visual tracking of the target it was deemed a non-search. And, while I think you can fairly quibble with that determination, if you accept it to be true, the question then becomes does GPS do anything more than mimic visual tracking. For me, the answer to that question has to be yes because the type of information collected by GPS tracking is qualitatively different than what beeper technology can do. Finally, even if you assume that GPS and beepers provide basically the same type of information, i.e., they are qualitatively indistinguishable, there can be little argument that they are worlds apart in terms of the quantity of information revealed. As the Court has said, when assessing intrusiveness (and the need for warrants) both quality and quantity count.

  3. Orin Kerr says:

    Thanks, Renee.

    If I can inquire a bit, what exactly is the information that a GPS reveals that a beeper does not that triggers the Fourth Amendment? Karo & Knotts focus on precisely what information is revealed, not the capacity of the device to reveal in the abstract. Thus, in those cases, a warrant is needed when a beeper reveals information about the inside of a home (karo) but not information that could be obtained in public (knotts). What’s the information that a GPS reveals that brings their use into the category of Karo rather than Knotts?

  4. Renee Hutchins says:

    I’ll take your second question first — doesn’t the Court look at information actually revealed, not information potentially revealed, to determine the extent of 4th Amendment protection. No. The way I read the decisions they set rules that guide police conduct as officers walk into the unknown future of any particular stop/search even though the cases themselves are necessarily triggered by and therefore grounded in a post-occurrence analysis of settled facts. So, an officer’s hand into a pocket on any given day is a search whether it comes out empty or not. Indeed, in Karo, the government argued that the rule established would require warrants every time a beeper was attached to a small mobile object. The Court’s response wasn’t “no, that’s not what we mean,” the Court’s response was “so what.”

    The differing results in Karo and Knotts are, I think, better justified along the lines of home v. everywhere else. The home has always enjoyed heightened 4th Amendment protection. And in Kyllo, the Court declared that the home is so special it is not subject to the intrusiveness analysis typically applied in other circumstances. Assuming that as the baseline, I read Karo as saying, even a technology that we’ve deemed to be just sense-enhancing (and therefore its use a presumptive non-search) will be treated differently when used inside a home.

    Okay, first question second. Because I tend to favor warrant protection I believe there is a qualitative difference between a technology that allows an officer to closely follow a single target and a technology that allows an officer to remotely track hundreds of targets simultaneously with pinpoint accuracy. But, I also concede that a fair argument can be made that the difference is really more quantitative than qualitative. Assuming that is true, though, even quantitative differences are important in the eyes of the Court. Intrusiveness doesn’t just consider what type of information is being disclosed, it also considers how much (think Dow Chemical or the drug field test cases). And, that is what draws a clear line between beepers and GPS devices, no?

  5. Orin Kerr says:


    Thanks for responding. I think the problem is that you are assuming that Fourth Amemdment principles that apply in one setting (Terry stops) apply in another (beepers). They don’t. The Fourth Amendment is highly localized: Very different rules apply in different settings. I explain this in detail in my article “Four Models of Fourth Amendment Protection” which runs through the four most common approaches. This is relevant because it means we can’t look to Terry stops to see what is consistent or inconsistent with Knotts and Karo: We need to look to the specific language of Knotts and Karo.

    As for your view that how much information is relevant under the Court’s cases, I disagree with that claim. Your examples are actually of the type of information mattering rather than the amount. The trick in Dow Chemical was that nothing too sensitive was obtained; in Jacobsen, the trick was that the information was limited only to whether or not drugs were present. In both cases, the Court rested the conclusion on the nature of the information obtained. I call this the private facts approach to Fourth Amendment protection in my Four Models paper, and I think it’s consistent with Knotts and Karo (as explained in the paper).

    As for your view about there being a presumption that sense-enhancing devices are non-searches (at least outside the home), I don’t see that in the Court’s cases. I don’t know of such a presumption; my sense is that the cases come out that way because the information is viewable to a member of the public, and thus is, in the Court’s view, not sufficiently deserving of privacy. Isn’t the same true with GPS information? My only experience with GPs is with a car, and it seems to operate just like a beeper. (Maybe I misunderstand the tech…)

  6. Renee Hutchins says:

    I completely agree, the Court does treat different settings differently. In the context of enhanced surveillance (and I use that term very loosely to include any implement, even dogs) the Court has said that the “intrusiveness” of the conduct matters. So, as early as Katz, the Court considered that the listening device at issue there revealed not just the volume of Katz’s voice or the number he dialed, but also “the words he uttered into the mouthpiece.”

    The Court’s concern about the type of information being revealed is played out in case after case following Katz. So, in Caceres, the Court gave extended discussion to the fact that the recording device was essentially a mechanical substitute for an agent’s contemporaneous notes. And, just a month later, the Court approved use of the pen register in Smith because it was “the modern counterpart of the operator who, in an earlier day, personally completed calls.” And in Kyllo, at least one distinction between the majority and dissenting outcomes is that the majority thinks the type of information revealed is not of the type that would ordinarily be available to human observation while the dissent contends that the information about internal temperatures could have been discerned by the unaided human senses.

    With regard to amount, I think your discussion of Dow Chemical and Jacobsen is certainly one possible characterization, but not the only one. In Dow Chemical the Court discussed “type” by equating the camera at issue there with “a simple flyover with naked-eye observation,” i.e., the information uncovered is the type of information the human senses can discern. The Court then turned from that discussion to a fuller discussion of not just type (naked-eye observations) but amount. Specifically, the Court talked about the “particularity” of the information contained in the photos. That the Court was referencing the degree of detail and not the nature of information seems clear from the Court’s subsequent comment regarding a potentially different outcome if more detailed photography was possible.

    Turning to Knotts a similar appreciation for the relevance of quantity seems apparent in the Court’s acknowledgement that it’s decision was not intended to authorize “twenty-four hour surveillance of any citizen.” In other words, if some device came along (like GPS) that allows much more information to be revealed than a beeper does (even if that information is arguably of the same type), Knotts by the Court’s own admission does not sanction its warrantless use.

    Lastly, regarding the contention that the Court typically treats sense-enhancing technology as a non-search, I think you’re right the Court has never been explicit in its endorsement of this view. But, it’s just beneath the surface of virtually every enhanced surveillance case the Court has decided. For a fuller discussion, see my article, Tied Up in Knotts? GPS Technology and the Fourth Amendment, 55 UCLA L. Rev. 409 (2007).

  7. Orin Kerr says:

    Thanks, Renee.

    I guess I’m still not sure exactly what the information is that a GPS reveals that a beeper doesn’t. Maybe I just misunderstand GPS technology, but it seems to me like pretty much just a beeper system. It’s a cheaper beeper system than ever before, more common and easier to implement (which cuts both ways, I think — more surveillance may mean more likely to be regulated, while more common arguably means less likely to be regulated under Kyllo), but ultimately just means for determining the physical location of the device just as in Knotts and Karo.

    You’re right about the line in Knotts about not authorizing total surveillance of the person, but it seems to pack a lot into that statement to say that GPS surveillance is an example of that 24 hours surveillance and therefore requires a warrant. In Karo a year later, the Court clarifies that what matters is what the device collects, not what it has the capacity to collect. If that’s right, the fact that location information comes from a GPS system instead of a beeper shouldn’t make a difference. The question should be how the device is used, not the capacity of the device in the abstract.

    Or so it seems to me. Anyway, thanks for the exchange.

  8. Richard Carey says:

    I am currently a Paralegal student that is looking on attending Law School. I have a current assignment, which is based on an actual case in Massachusetts that is going to the MA SJC, Commonwealth v. Connolly SJC-10355. April 2009 date for argument. Via Amicus Curiae

    In this case the Issues to be heard are:

    1. Challenge to the validity of a search warrant authotrizing GPS monitoring of the defendants vehicle

    A) whether GPS tracking constitutes a search or seizure relating to the Fourth Amendment.

    B) whether the defendant lacked a reasonable expectation of privacy in the movements of his vehicle on a public way.

    C) whether the execution of the warrant was valid under MA G. L. c. 276, s. 3A.

    This case differs from that of Garcia in the fact that the police did have a warrant.

    In my research I am finding Katz, Knotts, Karo, Kyllo, Lopez, McIver.

    I have reviewed the New modification to Rule 41, in the federal rules of criminal procedure.

    The Mock brief that I am required to write will be from the Appellee, the Government. In short I will argue That the lower court was correct in allowing the GPS monitoring, The Gps monitoring did not constitute a Search and Seizure under the Fourth Amendment, and was allowable under the MA G.L.c.276 s. 3A.

    There is little or no current “State Case Law” on this subject so Iwill be pointing to Case Law from other jurisdictions, and the Federal Courts. If you know of any “on point” case law that I should include in my research would you consider pointing me in that direction.

    I would very much like any assistance you might be able to provide. As a student I am looking on developing a list of experienced colleagues aspart of my “phone-mail” list.

    Thank-you for your time and best wishes for your career in the Law.


    Richard Carey