Sherry F. Colb

D.C. Circuit Holds that Month-Long Police GPS Monitoring Triggers Fourth Amendment

By SHERRY F. COLB
Wednesday, September 15, 2010

Last month, in United States v. Maynard, the U.S. Court of Appeals for the D.C. Circuit held that the Fourth Amendment "reasonable search" requirement applies to police when they track the movements of a person's car via an attached GPS device. In so holding, the D.C. Circuit joined a growing list of federal appellate courts that have opined on both sides of the question whether GPS-tracking constitutes a "search" for purposes of the Fourth Amendment's prohibition against unreasonable searches and seizures.

This question is likely to reach the U.S. Supreme Court before long, and it asks about the nature and extent of privacy that the Constitution grants us against government intrusion.

Reasonable Expectations of Privacy

In the 1967 case of Katz v. United States, the Supreme Court held that attaching a recording device to a public pay telephone to record conversations triggers the Fourth Amendment protection against unreasonable searches and seizures. The Court reasoned as follows: "[A] person in a telephone booth may rely upon the protection of the Fourth Amendment. One who occupies it, shuts the door behind him, and pays the toll that permits him to place a call is surely entitled to assume that the words he utters into the mouthpiece will not be broadcast to the world."

Technological advances have all but eliminated the phone booth, but the legal test that emerged from Katz lives on. To assess whether a method of surveillance qualifies as a Fourth Amendment "search," courts ask whether an individual who is engaged in the sort of activity at issue, under the circumstances in which he is placed under surveillance, has an expectation of privacy that society is "prepared to recognize as ‘reasonable.'" Stated differently, a "search" that triggers Fourth Amendment requirements (such as a prior warrant, probable cause, or reasonable suspicion) is something that invades a "reasonable expectation of privacy."

The word "reasonable," when applied to Fourth-Amendment-protected privacy expectations, generally has one of two meanings. The first and primary meaning is that the expectation is empirically sound: A person acting under the circumstances would be realistic in expecting to go unobserved.

If you leaned out of your window on a crowded street, for example, and loudly told your friend a secret about yourself, then your expectation of privacy in that confidence would be unreasonable, in this first sense. A police officer on that street accordingly would not be required to articulate any special justification for listening to what everyone else on the street could easily hear. As the Court has said, "the police cannot reasonably be expected to avert their eyes from evidence of criminal activity that could have been observed by any member of the public." Understood in this way, the Fourth Amendment protects against government intrusion upon the privacy that we could all realistically expect to have in the absence of state intervention. It thus leaves in place what we already have from our neighbors but does not prevent police from observing what is otherwise out in the open.

A second approach to the reasonableness of privacy expectations is to give the word "reasonable" a normative cast. Even though it might be unrealistic to expect privacy from one's neighbors under a particular set of circumstances, it might nonetheless be the sort of expectation that people in a free society ought to be able to have. If so, then the police might need to obtain a warrant to intrude in a manner that neighbors not only could, but routinely do.

One example would be police entering a house that is regularly subject to break-ins and invasions, because of the neighborhood and because of the residents' inability to afford an alarm system or a powerful enough lock for the door. The house's residents would, as a matter of empirical reality, have no good reason to expect privacy from other people. Yet the police must nonetheless obtain a warrant to enter the home and investigate, notwithstanding regular entries by non-governmental intruders.

Precedent for GPS Tracking -- and the Difference Between Single-Trip and Long-Term Monitoring Via GPS

The Supreme Court has not yet specifically ruled on the use of GPS tracking to monitor an individual's comings and goings, although several courts of appeals (including the Ninth Circuit, the Seventh Circuit, and the D.C. Circuit) have. The Supreme Court has, however, ruled on a related issue in United States v. Knotts. It held there that attaching a (much less technologically-advanced) tracking device to a container (which the target of the investigation purchased), and thereby monitoring the whereabouts of the car into which the container was placed, is not a search -- so long as the monitored car remains on the public streets, where it could be visually observed by anyone. The tracking device in Knotts did not broadcast its precise whereabouts (in the manner of a GPS), but it emitted signals that were picked up by a radio held by police who were following the targeted vehicle.

In concluding that such beeper monitoring did not constitute a Fourth Amendment search, a majority of the Court said that "[v]isual surveillance from public places … would have sufficed to reveal all of these facts [uncovered with the beeper] to the police. The fact that the officers in this case relied not only on visual surveillance, but also on the use of the beeper to signal the presence of [their target's] automobile to the police receiver, does not alter the situation." Stated differently, the Court said, "[a] person traveling in an automobile on public thoroughfares has no reasonable expectation of privacy in his movements from one place to another."

According to the Court, so long as someone is out in public, where anyone can see him, he has no reasonable expectation of privacy in his location. From this statement, one can infer -- and courts have inferred -- that a GPS device similarly invades no reasonable expectation of privacy, as long as its target is out in public. As in Knotts, in other words, what police are monitoring is something that is already observable with the naked eye by the public at large.

As the D.C. Circuit says, however, in distinguishing between Knotts and Maynard, twenty-four hour surveillance for extended periods of time is quite different from assisting police in following a vehicle on a trip from point A to point B. The D.C. Circuit notes in its opinion, for example, that the respondent's brief in Knotts specifically expressed the worry "that should [the Court] adopt the result maintained by the government, twenty-four hour surveillance of any citizen of this country will be possible, without judicial knowledge or supervision."

In response to this stated concern, from which the Supreme Court itself quoted in Knotts, the Justices said that "if such dragnet-type law enforcement practices as respondent envisions should eventually occur, there will be time enough then to determine whether different constitutional principles may be applicable." From this language, the D.C. Circuit concludes that the Supreme Court reserved for a later date the question now presented by long-term GPS monitoring.

But what is the affirmative argument for considering GPS surveillance an invasion of a reasonable expectation of privacy? The D.C. Circuit makes that argument well. It says that even if someone is likely to observe your car going from one place to another (perhaps by following you), the odds that anyone will be in a position to observe you in all of your travels for an entire month, as the police did to the respondent via GPS in Maynard, are very slim: "[T]he whole of a person's movements over the course of a month is not actually exposed to the public because the likelihood a stranger would observe all those movements is not just remote, it is essentially nil." The relevant probability of such observation occurring, absent police intervention, is, according to the D.C. Circuit, not the probability of somebody seeing the person each time he drives; it is instead the probability of the very same person seeing the driver on all of those occasions.

And why should that matter? If there will, in fact, be people observing you every time you drive on the public thoroughfares, then why is it important that the people will not be the same from one time to another? The answer, as the D.C. Circuit explains, is that "the whole reveals far more than the individual movements it comprises." Further, "[p]rolonged surveillance reveals types of information not revealed by short-term surveillance, such as what a person does repeatedly, what he does not do, and what he does ensemble…." It is empirically reasonable, in other words, for a person to expect "each of [her] movements to remain ‘disconnected and anonymous.'"

How Efficiency Itself May Render a Police Technique Invasive

The D.C. Circuit's arguments amount to a claim that the efficiency of the GPS, which allows it to assemble disparately-scattered "public" data, makes GPS monitoring objectionable. We reasonably rely, in other words, on the general anonymity that we enjoy, even in public. When a technology breaches that anonymity, it violates our privacy interests.

This argument is an appealing one. Most of us would find alarming the notion that our whereabouts from morning to night are being tracked by the police (or, in fact, by anyone). We would not, by contrast, find it surprising to learn that someone we know happened to see us somewhere, out in public, on one particular occasion (e.g., "Didn't I see you at Food For the Planet on Saturday?").

One problem with this argument is that the Supreme Court has not always accepted it in the past. In its 1971 decision in United States v. White, for example, the Court rejected a version of this argument in confronting the case of an informant conversing with an unsuspecting target while wearing a wire, and thus simultaneously transmitting the target's every word to the authorities.

In dissent, Justice Harlan said that "[t]he argument . . . that it is irrelevant whether secrets are revealed by the mere tattletale or the transistor, ignores the differences occasioned by third-party monitoring and recording which insures full and accurate disclosure of all that is said, free of the possibility of error and oversight that inheres in human reporting…. Much off-hand exchange is easily forgotten  and one may count on the obscurity of his remarks, protected by the very fact of a limited audience, and the likelihood that the listener will either overlook or forget what is said, as well as the listener's inability to reformulate a conversation without having to contend with a documented record." (Emphasis added).

In other words, according to Justice Harlan, the very efficiency of electronically monitoring and transmitting a consensual conversation (between an informant and a target) makes it an invasion of privacy that an ordinary consensual conversation between the same two people (later to be recounted to the authorities by the informant) would not be.

A majority of the Court in White, however, rejected Justice Harlan's argument, and a plurality spoke out in express praise of efficiency: "An electronic recording will many times produce a more reliable rendition of what a defendant has said than will the unaided memory of a police agent. It may also be that with the recording in existence it is less likely that the informant will change his mind, less chance that threat or injury will suppress unfavorable evidence and less chance that cross-examination will confound the testimony. Considerations like these obviously do not favor the defendant, but we are not prepared to hold that a defendant who has no constitutional right to exclude the informer's unaided testimony nevertheless has a Fourth Amendment privilege against a more accurate version of the events in question." (Emphasis added.)

One can easily see how the Supreme Court might say that a defendant with no constitutional right to exclude a police officer's unaided testimony about the defendant's locations, supplemented by a beeper, would similarly have no right to exclude the officer's testimony, aided by the more accurate and thorough version provided by a GPS device.

Much more recently than White, however, in its 2001 ruling in Kyllo v. United States, the Court held that using a thermal detection device to monitor heat patterns in a home (as part of an effort to identify a drug-cultivation operation) is a Fourth Amendment search, despite the fact that heat patterns in the home might sometimes become visible to the public by way of snow melting on the roof.

Getting a steady stream of information about the heat patterns inside a home would not be possible without either using technology or physically entering the home. And, by analogy, receiving a steady stream of information about a particular vehicle's whereabouts would not be possible (or at least remotely practical) without using technology such as a GPS device. This similarity may counsel in favor of the D.C. Circuit's conclusion in Maynard.

The Ultimate Decision

Ultimately, when the Supreme Court takes a case about whether GPS monitoring implicates the Fourth Amendment, it will have a choice. It has, as the D.C. Circuit suggested, reserved this very question, in Knotts. And it has, in earlier cases, made decisions that could support either outcome. It will therefore be in a position to decide, without departing from its precedents either way, whether a person against whom police lack sufficient suspicion to obtain a search warrant has a reasonable expectation of privacy in being free from around-the-clock GPS monitoring of his whereabouts in public. I, for one, hope that its answer is "Yes."


Sherry F. Colb, a FindLaw columnist, is Professor of Law and Charles Evans Hughes Scholar at Cornell Law School. Her book, When Sex Counts: Making Babies and Making Law, is available on Amazon.

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