The Supreme Court hears arguments Monday about a relatively new law enforcement technique that allows police to tap into giant tech-firm databases to find out who was near the scene of a crime and may have been involved. Essentially the question before the high court is whether that technique is ingenious, Orwellian, or both? And, ultimately, is it constitutional?

The technique is called geofencing, and it allows the government to draw a virtual fence around a geographic area where a crime was committed. After that, the government seeks a warrant, not to search a home or office, but to require a tech company to search its data to identify any of its millions of users who were within the geofence line at the time of the crime.

The geofencing in this case relied on a Google feature called 'location history.' Every two minutes, on average, the location feature recorded where you were by using multiple information sources to pinpoint and record the location of every person with an active cell phone. In other words, if you were within the geofence, and your phone was not turned off, Google could tell quite precisely where you were at any moment of the day or night.

Although Google has modified some of its geofencing policies, at the time this case began in 2019, about one-third of all Google users — some 500 million people — voluntarily opted into using the service, which also stored the users' information in Google's cloud, and could be accessed by law enforcement under a Google policy that required a warrant.

Can't see the video above? Watch it here.

"This was a little bit of an investigative lottery ticket when they had no other way of finding a suspect," says Stanford law professor Orin Kerr, who has written extensively about searches.

The focal point of Monday's case is the Fourth Amendment's ban on unreasonable searches of people, their homes, papers, and effects, unless police obtain a warrant issued by a neutral magistrate, and aimed at obtaining specific evidence of a crime.

How to understand a constitutional amendment from the 1700s in today's world

"The court has since the early 20th century grappled with the problem of what to do with advancing technology that shrinks the area of privacy that the Fourth Amendment was intended to protect," says Michael Dreeben, who has argued 109 cases in the Supreme Court, all but four on behalf of the Justice Department, and most of them involving criminal law. "One can sum up those cases by saying that when the court was asked to apply analog-era precedents to digital realities, it has uniformly favored privacy interests rather than extending precedents that allowed government searches."

In numerous cases, so far, he observes, the Supreme Court "concluded that in the modern era, it was indispensable to protect privacy of locational information derived from cell phones to avoid an arbitrary and Big Brother, dragnet-type surveillance by the government."

The geofencing case is the latest clash between privacy rights and law enforcement. It involves a bank robbery in the small Virginia town of Midlothian, where a robber pulled out a gun, and subsequently fled with $195,000.

Police immediately went to the scene, interviewed witnesses, and reviewed the bank's surveillance footage, where they saw a man who appeared to be the thief talking on his cell phone. But after two months of working the case, all leads had gone dry. So police applied for a geofence warrant directed at Google and all its collected and stored cellphone location information.

A state magistrate judge found probable cause to issue the warrant and authorized the disclosure of Google's location information for an area the size of about three football fields around the Midlothian bank at the time of the robbery. In other words, police could see who was where in the geofenced area at the time an hour before and after the heist took place. Google initially identified 19 cellphone users as potential suspects, but the company did not identify those individuals by name. In fact, Google pushed back at the request for so much information, and the company negotiated with the police to reduce their request from 19 unidentified users to nine and then just three cellphone users. At that point, Google agreed to unmask the identities of those three individuals, including Okello Chatrie, who subsequently was arrested. The other two identified users, as far as is known, were just innocent bystanders.

Sweeping up lots of folks

Of course, geofencing can sweep up lots of completely innocent people as suspects, and critics warn that geofencing could be used by the government to spy on law-abiding citizens engaging in, among other things, lawful protests and political activity.

Dreeben, the Justice Department veteran, acknowledges that in this case, lots of innocent people were driving to and from places within the geofence line. "They may have been going to church. They may have been seeing a psychiatrist. They may have been visiting a lover," Dreeben says. "And they are swept up in the geofence."

On the other hand, he notes that geofencing can be useful, as it was after the Jan. 6 Capitol riot, when federal law enforcement officers used geofencing to figure out which demonstrators clashed with police and invaded the Capitol, as opposed to those who were peaceably walking on the Capitol grounds.

In the Supreme Court, the Trump administration will tell the justices that because cellphone users voluntarily opted into Google's "location history" feature, they had waived any reasonable expectation of privacy. Indeed, the government contends that because the defendant took no steps to protect his location from disclosure, he has no right to privacy with or without a warrant.

Countering that argument is Adam Unikowsky, representing the defendant, who will tell the justices that not only is a warrant required; the warrant in this case was insufficient.

"At the Founding, people absolutely despised general warrants that would allow the police to search every single person's house without any suspicion," Unikowsky says. And that led to the constitutional amendment barring unwarranted and unreasonable searches of people's homes and effects.

"So we argue in this case that the warrant was unconstitutional because it allowed the government to search every single person's account for evidence of a crime, which is a little bit like searching every single person's house," Unikowsky explains.

The government replies that it is only searching one place: Google. But Unikowsky maintains that to find a needle in the Google haystack, Google had to sift through hundreds of millions of accounts. And that, he argues, is a dragnet, not a targeted search authorized by a judge.

"They say that if you put data in the cloud, you've just given it away to the cloud service voluntarily and therefore it's fair game for the government to come and get it," he says, adding, "If that's true, then a lot of data that we thought was safe, really wasn't."

But Dreeben, who for decades argued search and seizure cases on behalf of the government, summarizes the counter argument this way.

"The government's view is that Google is the place to be searched. It is Google servers that have the information the government is requesting," Dreeben says. The government therefore had reason to believe that "if this individual had opted into Google's location history, this would be a way to solve the crime."

Ultimately, he says, that the court will have two basic questions to answer. The first is whether a geofence is covered by the Fourth Amendment at all, and second is whether the millions of people who voluntarily signed up to have their location data stored for them essentially gave up any right to privacy.

"Even the government would concede, I think, that a travel diary like that, that's maintained for my benefit" by Google "is protected against arbitrary government action," Dreeben says.

An undetermined number of geofence warrants

Just how many geofence warrants have been issued in recent years is unknown. In 2020, for example, law enforcement served 11,500 geofence warrants on Google, according to Hofstra Law Review.

Monday's argument is likely to be only the beginning of these kinds of cases. Google has tried to head off any problems by changing where the data is stored. Now, it's on the user's devices, not Google's servers. But there are countless other questions that remain unanswered, including for instance, whether conversations with a chatbot psychiatrist, doctor, or travel adviser are protected from disclosure.

Google has filed a brief in this case that technically does not take sides, but it explicitly calls for a warrant requirement and takes the position that digital records should receive the same protections as physical records. Of course, Google is not the only tech company, and at some future point, the government might turn to other tech giants more willing to do what the government wants.

"The big question is going to be how easy it is to game for internet providers," says Stanford's Professor Kerr, who filed a brief in the case siding with the government. "We're in a computer world where so many of our records are stored remotely. Are all of our records protected? Every single thing we do? And if so, can that mean the government can never get a warrant for anything we do online?"

A decision in the case is expected by summer.