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The latest Supreme Court decision is being hailed as a big victory for digital privacy. It’s not.

Carpenter forces police to get a warrant before getting some cellphone data. But other Fourth Amendment cases will undermine its impact.

Photo of a hand holding a cell phone. Joan Cros Garcia/Corbis/Getty Images

Congratulations — a closely divided US Supreme Court has just ruled in Carpenter v. United States that you have a constitutional right to privacy in the locational records produced by your cellphone use. Law enforcement now cannot ask Sprint, AT&T, or Verizon, for cell tower records that reveal your whereabouts through your phone’s interaction with those towers, at least without a warrant.

Carpenter builds on two earlier decisions. In 2011, the Court required a warrant before police placed a GPS tracker on a vehicle to track its movements. In 2014, it forbade warrantless searches of cellphone during arrests. Whatever it’s other flaws, the Roberts Court thus seems to understand electronic privacy’s importance.

But there are a couple of things to know before toasting the Court’s high regard for privacy in the digital age. The Roberts Court, building on what the preceding Rehnquist Court did, has created an infrastructure for Fourth Amendment law that makes it exceptionally easy for police to do a search, even when a warrant is required. The law also makes it exceptionally difficult for citizens to obtain close judicial oversight, even when the police have violated the Constitution. As a result of these background rules, even a decision as seemingly important as Carpenter is unlikely to have any dramatic effect on police practices.

It’s not just that our digital privacy is insufficiently protected, in other words. It’s that our Fourth Amendment rights and remedies in general have been eroded. Once enough holes have been poked in the general system for vindicating Fourth Amendment interests, the decision to extend Fourth Amendment coverage to a new domain — such as cell-site locational data — is just not terribly significant.

Timothy Ivory Carpenter had been convicted of nine armed robberies based on witness testimony, but the prosecution also stressed in its closing argument records obtained from his cellphone company. Those records showed how Carpenter’s phone interacted with the cell phone towers that carried its signal. As Chief Justice Roberts emphasized, the records painted a detailed picture of Carpenter’s movements over 127 days.

Yet the government did not use a warrant based on probable cause to obtain those cell-site records, relying instead on a statute called the Stored Communications Act.

Forcing police to get a warrant is not much of a protection these days

Consider first the core constitutional protection on which Chief Justice Robert’s opinion in Carpenter hinged — the requirement of a warrant based on probable cause from a judge before the police can acquire cell-site records that allow for detailed physical tracking of suspects’ movements.

From now on, the police will usually have to get a warrant before seeking such information. But that offers limited protection. One reason: In other Fourth Amendment cases, the Court has held that it is not just life-tenured federal judges who can issue warrants. A warrant can also be obtained from a range of other officials, including municipal court clerks who have no law training and no tenure protection. Such clerical staff lack the skills and incentives to examine warrant applications closely to determine compliance with the law. Still, they are allowed to issue warrants.

Even where there are no such court clerks, it is well known that police and prosecutors go “judge shopping” when a physical search or arrest is in play. Judges have varying reputations for being more or less careful in scrutinizing warrant applications. It is often well known which judges in a city or courthouse are more or less scrupulous. When police have a weak warrant application, they have a strong incentive to avoid judges who will give it a close read.

These weaknesses in the warrant regime for physical searches or arrests are exacerbated when electronic data is at issue. Warrant applications for cell tower records often rest on technical details about the geographic and temporal scope of the search. These applications might in theory seek a quite varied range of information, including the target’s location, the number of calls he made, and the manner in which he used apps.

Review of the application will also require fine judgments about when information can be shared with other law enforcement agencies and government officials. Just because a prosecutor can obtain electronic data, for example, that surely doesn’t mean she can hand it over to, say, a political appointee in the White House or a Department of Transportation employee who happens to be the subject’s boyfriend.

Because close scrutiny by an experienced and independent judge has become so easy to avoid, there is no guarantee these questions matters will get careful and independent consideration — even if a warrant is sought and issued consistent with the main holding of Carpenter.

The hurdle of “probable cause” has also been steadily lowered

Assume that police are before a scrupulous judge. Even then, the background Fourth Amendment rules mean that they have a light burden to bear. As Chief Justice Robert’s opinion today stresses, a warrant can be issued only based on “probable cause.” But in a series of earlier cases about physical searches, the Court has winnowed down the “probable cause” requirement to the showing of a mere “fair probability” that evidence of a crime will be found.

This “fair probability” requirement has become easier to satisfy in recent decades because federal and state legislatures have created sweeping penalties for conspiracies to commit crimes and for accomplices.

Showing a “fair probability” of a conspiracy to commit a crime is not difficult. Under federal law, for example, a criminal conspiracy exists if there’s an agreement to commit any criminal act in the future, and one step — even a lawful one — taken to that end. In one case, for example, a Google search served as the “overt act” for an elaborate conspiracy charge, even in the absence of evidence of actual planned criminal conduct.

This sweeping definition of criminal liability interacts with the weak “probable cause” rule. Police need only show a “fair probability” that a single lawful action has been taken in relation to a criminal agreement, and they are entitled to a warrant. This is not hard to do.

This problem is pervasive across Fourth Amendment law. But it has particular significance to cell-site locational data. Such data maps the movements of a group of people — precisely the evidence that is routinely relevant to conspiracy charges. So with a conspiracy theory in hand, it will often be very easy for the police to meet the (exceedingly weak) probable cause standard.

Would a warrant requirement have made a practical difference in Carpenter’s case?

In Carpenter’s case, investigators had a confession from one of the participants in the string of armed robberies. They also had the cell numbers of other participants, including Carpenter’s. These two pieces of information would almost certainly have been enough to allow the government to get a warrant on a conspiracy theory of probable cause.

But imagine that the investigator couldn’t even pull together evidence showing probable cause of a conspiracy. Imagine that they instead play fast and loose with the contents of the warrant application. For example, the application might rest on some dubious evidence, and the investigator might consciously choose not to confirm its accuracy. Once charges have been filed, could a defendant get the locational data thrown out on the grounds that the warrant application was based on false pretenses?

Once again, general Fourth Amendment law makes this possible in theory but unlikely in practice. To get evidence acquired by a warrant tossed out of court, a defendant must show that an investigator acted with “reckless disregard” in preparing a warrant application. In most states and in federal court, there is no rule that permits the defendant to examine police or prosecutor records. Hence, the defendant often must make this recklessness showing without any documentary evidence of what the police did.

It is therefore usually practically impossible for most defendants to challenge flawed search warrants. Again, warrants for electronic data are no different.

Even if a defendant succeeds in getting a warrant quashed, moreover, the Supreme Court has said that a reviewing court of appeals must look again at the warrant — now placing a thumb on the scales in favor of the investigating officer. In effect, when the government loses the rare case in which a defendant can show a warrant to be flawed, it gets a second chance to have the warrant restored by a court of appeals.

Prosecutors can use illicitly obtained information if a suspect testifies

Still, lean your imagination into the wind to imagine a defendant who has overcome all these constraints, and had a warrant quashed. The evidence from that flawed warrant can still be introduced at trial if the defendant chooses to testify. The Supreme Court established that rule in the 1971 case of Harris v. New York, on the grounds that if the defendant could give testimony, the government had the concomitant right to undermine it by whatever information was in its hands.

As a result, even when the government has illegally acquired evidence, its possession of that evidence creates a strong incentive for defendants not to take the stand. Needless to say, this will often make the prosecutor’s job easier.

If a defendant chooses not to testify, that is still not the end of the story. The government can also argue that information gathered unlawfully without a warrant should be admitted because there was an emergency. Chief Justice Roberts explicitly carved out an emergency exception in his Carpenter opinion, citing the possibility of “bomb threats, active shootings, and child abductions.” In such cases, no warrant is required.

Also, if the locational data was acquired without a warrant before Carpenter was decided, the Court held that it need not be kept out. Carpenter hence helps no one whose cell-site locational data was acquired before this week. And the Carpenter opinion also leaves open the possibility that police can acquire less than seven days of cell-site data without a warrant.

Are there other paths for redress? Someone in Carpenter’s shoes, whose Fourth Amendment rights have been violated, can technically sue the police for damages even if they are not charged with a criminal offense. The problem is that the Court has almost completely squelched the availability of damages for most constitutional wrongs, including the Fourth Amendment, through a series of technical anti-plaintiff rules.

In short, the legal framework of Fourth Amendment remedies has been riddled with so many exceptions and loopholes that Carpenter’s holding that a warrant is required to acquire cell-site locational data is likely to impose no great burden on the police.

If police can’t get the information through cellphone companies, they will turn up the heat on suspects

But the facts around the electronic data in Carpenter make the Court’s holding especially hollow. Locational data is held not only by telephone company. It is also contained on a person’s phone, even if she chooses to disable locational tracking. (Certain apps can track locational data produced by a phone’s internal sensors without the owner’s knowledge or permission.) This data is generally accurate to a foot or so.

Police can thus acquire location data — and much more — if they ask for consent to examine a phone. Extensive psychological research shows that most of the time —especially if the suspect is a woman or a racial minority — suspects are likely to say yes.

General Fourth Amendment law says police can seek consent to make a search. In the physical search context, the Court has consistently ignored the fact that people often feel they have no choice but to acquiesce.

Consider the leading Supreme Court case on consent searches, United States v. Drayton. Two men are traveling by bus in Florida, when police board the bus and question passengers about their trip. The first man is asked to “consent” to a pat down. He does — and the officer finds blocks of cocaine taped to his groin. After this first man is led away in handcuffs, the officer turns to his traveling companion and says, “Mind if I check you?” The second man agrees. Drugs are found in exactly the same spot on his body. The Supreme Court holds that he consented to the search.

My students, encountering Drayton for the first time, often have a moment of cognitive dissonance. Why, they wonder, did the suspect consent after he saw what happened to his friend? When I point out that both men were racial minorities in a jurisdiction with a history of police violence, and that neither was highly educated nor socially privileged, then the facts start to make more sense.

Ironically, the Carpenter decision makes it more likely that police will aggressively exploit the weaknesses of the Court’s consent case-law. By making it slightly more hassle to obtain cell-site locational data from a telephone company, the Court has encouraged police to exploit the frailty of its consent doctrine. That is, by making it harder to acquire electronic data from a third party, the Court has nudged police toward more forceful and unpleasant confrontations with citizens by which “consent” can be secured.

This should not count as a “success” for Fourth Amendment freedoms.

Electronic privacy rests on the rules and remedies that apply to the Fourth Amendment generally. In the past 40 years, those rules and remedies have been substantially eroded by a Court unwilling to constrain police.

The result today is that even when a decision endorses Fourth Amendment protection —and requires a warrant, as in Carpenter — that protection is easy to avoid, and likely ineffectual in practice.

Aziz Huq is the Frank and Bernice J. Greenberg professor of law at the University of Chicago Law School.

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