One Way or Another, I’m Gonna Find Ya: The U.S. Supreme Court Considers Whether GPS Tracking of Suspects’ Cars Requires a Search Warrant

Posted in: Constitutional Law

This November, the U.S. Supreme Court will hear argument in United States v. Jones, which The New York Times described as “the most important Fourth Amendment case in a decade.”

Jones asks the Court to determine whether police who track a suspect’s movements over time with a global positioning system (GPS) device that they have attached to his vehicle intrude on the suspect’s Fourth Amendment right against unreasonable searches and seizures.

Lower federal courts have split over the issue, and prior Supreme Court precedents raise the prospect that such tracking may fall entirely outside the scope of Fourth-Amendment-protected privacy.  If the Court takes this view, then police will be able to use GPS devices to track any vehicle for any length of time without having a concrete basis for suspecting the target of criminal wrongdoing.

This column asks:  What would happen if the Court decided Jones in favor of privacy—holding, therefore, that GPS tracking requires a warrant?  Would this ruling protect people against the kind of surveillance that GPS devices enable?  The answer, I will suggest, may be “No.”

Tracking Devices and Supreme Court Precedents

In 1983, in United States v. Knotts, the Supreme Court held that police could lawfully attach a beeper (a primitive tracking device) to a container that they knew would later come into a suspect’s possession, an installation that enabled law enforcement personnel to follow the suspect’s movements with greater precision than they could have achieved without technological assistance.

In Knotts, police followed the suspect’s car (into which the suspect had, by then, placed the container with the attached tracking device), and the concealed beeper let police know whether they were getting closer or further from the suspect during the particular trip.  This meant that when police lost sight of the vehicle that they were following, they could catch up with the suspect’s car and maintain a successful “tail.”

In Knotts, the Court found that because the beeper in question exposed only what was already visible to any member of the public—the car’s location at a particular public spot at a given time—the beeper’s use by police could not be said to have invaded any reasonable expectation of privacy on the part of the driver.

Stated differently, the Court found that driving a car on the public roads “knowingly exposes” to all and sundry the whereabouts of that car.  And what people knowingly expose to the public—what any private citizen may readily observe—is not legitimately characterized as “private” from the government’s observation.

From Beepers to GPS Devices

As I have discussed at length in two columns on the subject, here and here, there is arguably a big difference between using the sorts of beepers evaluated in Knotts, and using a GPS tracking device.  Beepers slightly enhance the government’s ability to physically follow a suspect’s car on individual trips.  GPS devices, in contrast, allow a government office to keep detailed records of everywhere a vehicle is, at all times.

Following a vehicle one time, as a beeper-trailing police car does, is likely to convey only limited information about the driver’s life.  On the other hand, keeping an ongoing tally of every trip the driver makes, which is what GPS devices allow, conveys a wealth of information.  This information could well include much of what the driver considers personal and private:  how much of the day she spends working; with whom she spends most of her spare time; whether she is in treatment for a sexually-transmitted disease, a mental illness, and/or a substance addiction; whether she is pregnant and what she plans to do about the pregnancy; and what kinds of activities she pursues in her free time.

Thus, from the perspective of a person subject to this kind of surveillance, the use of a GPS device could feel very much like government spying, inflicting a serious intrusion into what people typically take to be their personal space and privacy as they make their way through their lives.

GPS Devices Provide a Cumulative, Unified Picture Extending over Time

The U.S. Court of Appeals for the D.C. Circuit (and dissenters from other federal courts of appeals decisions) have identified as dispositive for Fourth Amendment purposes the distinction between the “snapshot” of a life facilitated by the beeper technology and the cumulative “motion picture” developed through a GPS device.

After all, the “exposure” that most of us experience by venturing out in public in our vehicles ordinarily does not reveal information to the same person (or entity) from one trip to the next.  Though one acquaintance might notice that you visited the hospital last Monday evening, since she too was parked in the lot there, it is likely to be a different acquaintance (or no one you know at all) who sees you entering an “adult” book store the next day.  It is accordingly not accurate to say that people are already “exposed” to a cumulative and unified record of their every trip, simply by virtue of their having driven on the public roads.

The idea behind “knowing exposure” as a baseline for Fourth Amendment privacy is that the police are generally required to refrain from invading only that privacy which exists before police come on the scene.  For example, because no one else can hear what you say when you talk on the telephone with a friend, the police also may not—without probable cause and a warrant—listen to what you say, via a wiretap.  When, on the other hand, you yell personal information out the window of your house at a volume that everyone on the street can hear, the police need not plug their ears so that they do not hear you; in this instance, they can listen along with all of your neighbors.

Police, in the absence of a search warrant or other justification for invading your privacy, are thus required to honor your privacy to more or less the same degree that other members of the public do.  And, conversely, what other members of the public see and hear is a legitimate target of surveillance for the police as well.

It seems contrived, however, to claim that people driving on the roads are “exposed” to private citizens in a manner that is comparable to the exposure imposed by a GPS device’s recording of every trip over an extended period of time.

Suppose the Supreme Court agrees with me and other commentators, and with the U.S. Court of Appeals for the D.C. Circuit, and rules that police must obtain a warrant based on probable cause before attaching a GPS device to a vehicle.  What then?

Requiring a Warrant and Probable Cause for the Use of GPS May Compromise “Innocent Privacy”

For reasons that I will elaborate below, a decision to require a warrant and probable cause for the use of GPS devices will not necessarily inure to the benefit of what we might call “innocent privacy,” defined as the privacy of innocent people.

To elaborate a bit, we can understand “innocent privacy” in this way:  If the Fourth Amendment is functioning as it should, then it will maximize the degree to which innocent people—people who have done nothing criminal—enjoy freedom from governmental invasions of their privacy.

Beyond this, the phrase “innocent privacy” can also refer to the privacy of everyone—including even people who have committed criminal acts—for the innocent but personal parts of their lives.  In the case of someone who is guilty of a crime, in other words, police ideally should leave undisrupted as much of his privacy as is consistent with locating evidence of the crime.

Therefore, even if it is clear that X has stolen a television set, and though police might be fully authorized to search his home for the TV, X is nonetheless entitled to keep the police from, say, reading his personal diary or perusing his medicine cabinet during that search.  His privacy in these things deserves protection, to the extent that the protection does not impede the search for evidence of theft, because it shields what is innocent in X’s life.

Why do I mention innocent privacy here?  The first thing to note, in answering this question, is that it is possible for the police to electronically track a person’s movements without having to attach a GPS to her vehicle.  The overwhelming majority of people who live in the United States own and use cell phones. (Indeed, increasing numbers of people do not even have a landline at home.)  If police can monitor the location of people’s cellphones, such monitoring accordingly provides at least as much location information as would monitoring vehicles via GPS.

So what?, readers may ask  Wouldn’t attaching a GPS device to a cell phone trigger the same Fourth Amendment protection as attaching a GPS device to a car?  Why distinguish between cars and cell phones in this regard?

The answer to this question is that there may be Fourth Amendment equivalence between the two, but only if police have to attach something new to people’s cell phones.  In reality, however, many cell phones already contain tiny GPS units inside them, and for those that do not, phone calls are routed through cell towers that enable precise determinations of where a phone is at a given time.

Providers of wireless service, such as Verizon and AT&T, therefore have ready access to detailed information about their customers’ whereabouts most or all of the time.  And by asking providers to share their records, government officials can acquire that detailed information.

The reader may be thinking that the Fourth Amendment would require the government to seek a warrant, based on probable cause, before being able to ask providers for cell phone location records.  That is because making a request of this sort seems essentially equivalent to attaching a GPS to a car and then tracking its journey, and we have been assuming for purposes of this column that the Supreme Court holds in Jones that attaching a GPS device to a car requires a warrant.  But it is quite likely, as I will explain, that the Court would treat the GPS and cellphone issues as separate and distinct from each other, for Fourth Amendment purposes.

Why the Supreme Court Might Require a Warrant for a Car’s GPS, but Not for Cell Phone Location Records

Though the conclusion that a warrant based on probable cause would be necessary to acquire cell phone location information is defensible as a matter of logic, there is good reason to think that existing Supreme Court precedents do not support such a requirement.  Cases on the books, in other words, would not appear to treat a police department’s request for a customer’s telephone records as a “search” of the cellphone patron under the Fourth Amendment, regardless of how Jones were decided.

In 1979, Smith v. Maryland, the Supreme Court said that the government may—without a warrant—ask the telephone company to keep a running record of the telephone numbers called from an individual’s home.  The reason, the Court explained, is that whenever a person makes a call from her phone, she voluntarily conveys the numbers that she dials to the telephone company.  By voluntarily sharing this information with the phone company, the Court reasoned, the individual assumes the risk that the phone company will pass it along to others, including the government.  That is, when making a phone call, a person “knowingly exposes” the number he is calling and therefore has no Fourth Amendment interest in keeping it secret from the government.

In an earlier ruling in 1976, the Court had said the same thing about bank records—holding, in United States v. Miller, that they are “voluntarily conveyed to the banks and exposed to their employees in the ordinary course of business. . . .  The depositor takes the risk, in revealing his affairs to another, that the information will be conveyed by that person to the Government.”

Carrying the logic of these decisions over to the present time, it is equally true that by owning and carrying around a cellphone, a person conveys to her carrier not only the telephone numbers that she calls (as in Smith), but also the various locations to which she brings her phone.

Thus, the Supreme Court would have to reverse or significantly adjust existing precedents (beyond Knotts) to reach the conclusion that asking wireless providers for records of patrons’ cell phone locations qualifies as a Fourth Amendment “search” requiring probable cause and a warrant.

The government has already apparently been quite busy making these sorts of inquiries of wireless providers.  As reported by a Ninth Circuit dissent, in 2009, “law enforcement agents pinged users [i.e., sought the signals identifying the locations of users’ cell phones] of just one service provider—Sprint—over eight million times….  The volume of requests grew so large that the 110-member electronic surveillance team couldn’t keep up, so Sprint automated the process by developing a web interface that gives agents direct access to users’ location data.”

On the authority of a federal statute, the Stored Communications Act,  judges have ordered companies to produce such records when prosecutors contended that the records were relevant and material to an ongoing criminal investigation—a standard that falls short of the “probable cause” required for a search warrant under the Fourth Amendment.

And this point, finally, brings us back to innocent privacy.  If you are an innocent person, then you probably use your cellphone under a plan for which you have signed up.  Under existing precedents (precedents separate from Knotts), you have thereby “knowingly exposed” your ongoing location information to strangers (by exposing it to your carrier) and you have accordingly relinquished any Fourth Amendment interest in keeping that information secret from the police.  For this reason, you—an innocent person—will likely have no legal basis for resisting a government’s request that your provider record and hand over cellphone records.

On the other hand, if you are engaged in a criminal enterprise, then you may be inclined to take the time to purchase one or more disposable, untraceable cell phones.  These phones are pre-paid and set to expire.  By using a disposable phone, a perpetrator makes it difficult for police to find out his whereabouts at any given time, because he does not continually broadcast location information to an identifiable wireless provider.

To learn where this person goes, police may therefore need to attach a GPS device to his vehicle, which—under our hypothetical future Supreme Court decision in Jones—will require a warrant based on probable cause.  As a consequence, then, police will have an easier time discovering the detailed travels of people who are not engaged in criminal activity (through their cell phones, with no warrant or probable cause needed) than they will have in tracking people who are, in fact, engaged in criminal activity (through GPS devices attached to their cars by way of a warrant and probable cause).

The perverse consequence is to extend greater Fourth Amendment protection to guilty people than to innocent ones, by virtue of guilt.

What Should Be Done To Guard Innocent Privacy?

I may be right about the consequences for innocent privacy of our hypothetical ruling in Jones—which would read the Fourth Amendment to cover GPS car tracking.  Even so, I would nonetheless urge the Court to rule for the respondent in Jones, and thus hold that warrants based on probable cause are required for GPS surveillance.

Why?  Because tracking a vehicle’s movements on the public roads over time is highly intrusive.  It exposes an otherwise hidden narrative of a person’s life—a narrative that should remain secret in the absence of probable cause to suspect wrongdoing.

Understanding the separate threat of cell phone location surveillance, in turn, enables us to see that even if it decides Jones for the respondent, the Court will still have work to do to secure locational privacy for the vast number of Americans who own and use cellphones.

It is accordingly useful to view Jones as the opportunity for a first step—without which everyone is vulnerable, because if attaching a GPS to a vehicle is not a search, then neither is asking Sprint for cellphone location records.

In the event that the U.S. Supreme Court takes this first step, the next—and crucial—step would involve recognizing the following:  Wireless carriers hold private information for individual patrons; patrons do not in any meaningful sense “knowingly expose” this information to the public; and providers thus hold a position of trust regarding personal information.

So long as the Court fails to hold that a warrant based on probable cause is required prior to disclosure of the kind of information available to wireless carriers, the carrier’s position of trust, and the privacy that it guards, will remain vulnerable and “the people” correspondingly less “secure . . . from unreasonable searches and seizures.”