The Supreme Court can't save digital privacy

Carrying a smartphone, it's hard to get lost. But the connection works both ways: If you can always find your location, you can always be found.

That simple equation was at issue in this week's Supreme Court decision in Chatrie v. United States. The justices decided, correctly, that the Constitution protects the privacy of the location data our phones constantly transmit. Still, the opinion has a whistling-past-the-graveyard quality, a struggle to find legal protection for what technology has already sent into the wild.

Chatrie involved a "geofence," a virtual perimeter, which combined with location data can say which phones were where at a given moment. A geofence warrant commands the possessor of the data (in the court's words): "Tell us, through cell-phone location data, who was there when a crime happened." The easiest way to understand how the process works is to review the facts of Chatrie. As it happens, that's also the easiest way to understand the greater threat to privacy.

So, the facts: In 2019, an armed man stole $195,000 from a credit union. The police soon discovered that the robber, shortly before entering the building, had spoken on his cell phone. A magistrate issued a warrant requiring Google to supply anonymized location data for all cell phones within 150 meters of the credit union - the geofence - for half an hour before and after the robbery.

Using this data, investigators narrowed their search of phone numbers but broadened the time period. That fresh data enabled police to determine that the robber was one of three users. At that point, the warrant required Google to disclose the names of the three. One was Okello Chatrie, who, after further investigation, was indicted for the crime and subsequently convicted.

The question before the justices was whether, by obtaining the records, the police violated Chatrie's right under the Fourth Amendment to be free from an unreasonable search. Justice Elena Kagan's opinion for the court answered the first part of the question - yes, she concludes, demanding the location data from Google constituted a search - but left to the lower courts the decision on whether the search was reasonable.(1)

What makes the demand a search? The fact that "an individual has a legitimate expectation of privacy in his cell-phone location data." At first blush, this conclusion seems counterintuitive. When we turn on location services, we enable ride-sharing services and retailers alike to find us. The map app won't yield useful information unless allowed to know where we are. We're constantly sharing our location with corporations galore, who store and preserve it. How can we reasonably expect the data to remain private?

Here Justice Kagan's opinion relies heavily on the court's 2018 decision in Carpenter v. United States, which found that a search had occurred when law enforcement obtained from a cellular provider the data on which cell towers a particular individual's phone had pinged, enabling investigators to trace nearly all of his movements over a period of 127 days. The location data demanded in Chatrie was even more fine-grained, pinpointing the defendant's location "within around twenty meters, which is less than two percent of a mile." This constitutes a search, Kagan writes, because it sweeps in so much of his life:

What creates that concern is that the government can access all of a cell-phone user's movements, in both public and private places - that it possesses a virtual panopticon with which to scrutinize its citizens' activities.

The imagery is intentionally Orwellian - one can see the Thought Police huddling - but it doesn't quite get us to the end. Courts have consistently held that people do not have a reasonable expectation of privacy in various information they voluntarily entrust to third parties. A common example is financial records.

In Chatrie, the government argued that even if cell phones are ubiquitous, giving location data to the carrier is voluntary. The user can turn the feature off. Justice Kagan's response: "But that is to imagine that all of us are living in dumb flip-phone days. The point of carrying smartphones is to use what is on them." In other words, the very ubiquity of our phone addiction makes the data private.

To be sure, reasonable minds might differ. Here is Justice Neil Gorsuch, who concurred in the result but disputed the majority's reasoning:

Why does tracking Mr. Chatrie's movements digitally over an hour or two invade his reasonable expectation of privacy when an officer tailing him for the same length of time would not? ... Why is Location History data Mr. Chatrie voluntarily shared with Google not 'truly shared' when a person's bank records are?

I think Justice Gorsuch is right. But Justice Kagan is also right. The point is that we live in a world where being tracked, recorded and observed is simply the background condition of life. One can hardly drive down the street without being recorded by traffic cameras in the roughly half the states where they're legal, and if the traffic camera misses us, the security cameras, building by building, will surely capture our images. And throughout the day, whether within our abodes or out and about, we choose to carry upon our persons the most powerfully intrusive surveillance instrument ever devised. We turn over to corporate guardianship vast swaths of our lives.

Of course law enforcement would like that data. One can easily imagine less scrupulous government departments demanding it as well. To call the data private is a useful legal conclusion, but, as technology advances, constitutes little more than a holding action - not least because younger generations seem to be unconcerned about the problem. Still, the true threat to privacy is not government demands for our data, but our willingness to live under constant surveillance.

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(1) Justice Alito's dissent makes a plausible argument that the United States Court of Appeals for the Fourth Circuit already decided the question of reasonableness; if he is right, then the Supreme Court should have dismissed the appeal.