Being out in the world advocating for privacy often means having to face a chorus of naysayers and nihilists. When we spend time fighting the expansion of Automated License Plate Readers capable of tracking cars as they move, or the growing ubiquity of both public and private surveillance cameras, we often here a familiar refrain: “you don’t have an expectation of privacy in public.” This is not true. In the United States, you do have some expectation of privacy—even in public—and it’s important to stand up and protect that right.
How is it possible to have an expectation of privacy in public? The answer lies in the rise of increasingly advanced surveillance technology. When you are out in the world, of course you are going to be seen, so your presence will be recorded in one way or another. There’s nothing stopping a person from observing you if they’re standing across the street. If law enforcement has decided to investigate you, they can physically follow you. If you go to the bank or visit a courthouse, it’s reasonable to assume you’ll end up on their individual video security system.
But our ever-growing network of sophisticated surveillance technology has fundamentally transformed what it means to be observed in public. Today’s technology can effortlessly track your location over time, collect sensitive, intimate information about you, and keep a retrospective record of this data that may be stored for months, years, or indefinitely. This data can be collected for any purpose, or even for none at all. And taken in the aggregate, this data can paint a detailed picture of your daily life—a picture that is more cheaply and easily accessed by the government than ever before.
Because of this, we’re at risk of exposing more information about ourselves in public than we were in decades past. This, in turn, affects how we think about privacy in public. While your expectation of privacy is certainly different in public than it would be in your private home, there is no legal rule that says you lose all expectation of privacy whenever you’re in a public place. To the contrary, the U.S. Supreme Court has emphasized since the 1960’s that “what [one] seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected.” The Fourth Amendment protects “people, not places.” U.S. privacy law instead typically asks whether your expectation of privacy is something society considers “reasonable.”
This is where mass surveillance comes in. While it is unreasonable to assume that everything you do in public will be kept private from prying eyes, there is a real expectation that when you travel throughout town over the course of a day—running errands, seeing a doctor, going to or from work, attending a protest—that the entirety of your movements is not being precisely tracked, stored by a single entity, and freely shared with the government. In other words, you have a reasonable expectation of privacy in at least some of the uniquely sensitive and revealing information collected by surveillance technology, although courts and legislatures are still working out the precise contours of what that includes.
In 2018, the U.S. Supreme Court decided a landmark case on this subject, Carpenter v. United States. In Carpenter, the court recognized that you have a reasonable expectation of privacy in the whole of your physical movements, including your movements in public. It therefore held that the defendant had an expectation of privacy in 127 days worth of accumulated historical cell site location information (CSLI). The records that make up CSLI data can provide a comprehensive chronicle of your movements over an extended period of time by using the cell site location information from your phone. Accessing this information intrudes on your private sphere, and the Fourth Amendment ordinarily requires the government to obtain a warrant in order to do so.
Importantly, you retain this expectation of privacy even when those records are collected while you’re in public. In coming to its holding, the Carpenter court wished to preserve “the degree of privacy against government that existed when the Fourth Amendment was adopted.” Historically, we have not expected the government to secretly catalogue and monitor all of our movements over time, even when we travel in public. Allowing the government to access cell site location information contravenes that expectation. The court stressed that these accumulated records reveal not only a person’s particular public movements, but also their “familial, political, professional, religious, and sexual associations.”
As Chief Justice John Roberts said in the majority opinion:
“Given the unique nature of cell phone location records, the fact that the information is held by a third party does not by itself overcome the user’s claim to Fourth Amendment protection. Whether the Government employs its own surveillance technology . . . or leverages the technology of a wireless carrier, we hold that an individual maintains a legitimate expectation of privacy in the record of his physical movements as captured through [cell phone site data]. The location information obtained from Carpenter’s wireless carriers was the product of a search. . . .
As with GPS information, the time-stamped data provides an intimate window into a person’s life, revealing not only his particular movements, but through them his “familial, political, professional, religious, and sexual associations.” These location records “hold for many Americans the ‘privacies of life.’” . . . A cell phone faithfully follows its owner beyond public thoroughfares and into private residences, doctor’s offices, political headquarters, and other potentially revealing locales. Accordingly, when the Government tracks the location of a cell phone it achieves near perfect surveillance, as if it had attached an ankle monitor to the phone’s user.”
As often happens in the wake of a landmark Supreme Court decision, there has been some confusion among lower courts in trying to determine what other types of data and technology violate our expectation of privacy when we’re in public. There are admittedly still several open questions: How comprehensive must the surveillance be? How long of a time period must it cover? Do we only care about backward-looking, retrospective tracking? Still, one overall principle remains certain: you do have some expectation of privacy in public.
If law enforcement or the government wants to know where you’ve been all day long over an extended period of time, that combined information is considered revealing and sensitive enough that police need a warrant for it. We strongly believe the same principle also applies to other forms of surveillance technology, such as automated license plate reader camera networks that capture your car’s movements over time. As more and more integrated surveillance technologies become the norm, we expect courts will expand existing legal decisions to protect this expectation of privacy.
It’s crucial that we do not simply give up on this right. Your location over time, even if you are traversing public roads and public sidewalks, is revealing. More revealing than many people realize. If you drive from a specific person’s house to a protest, and then back to that house afterward—what can police infer from having those sensitive and chronologically expansive records of your movement? What could people insinuate about you if you went to a doctor’s appointment at a reproductive healthcare clinic and then drove to a pharmacy three towns away from where you live? Scenarios like this involve people driving on public roads or being seen in public, but we also have to take time into consideration. Tracking someone’s movements all day is not nearly the same thing as seeing their car drive past a single camera at one time and location.
The courts may still be catching up with the law and technology, but that doesn’t mean it’s a surveillance free-for-all just because you’re in the public. The government still has important restrictions against tracking our movement over time and in public even if you find yourself out in the world walking past individual security cameras. This is why we do what we do, because despite the naysayers, someone has to continue to hold the line and educate the world on how privacy isn’t dead.
