The Supreme Court’s ‘Reasonable Expectation of Privacy’ Test Defies Expectations

When he was arrested in 1965, Charles Katz “was probably the preeminent college basketball handicapper in America.” Or so says Harvey Schneider, who presumably should know, since he later represented Katz at the Supreme Court in a landmark Fourth Amendment case.

The Court’s 1967 decision in Katz v. United States, which held that the Constitution’s prohibition of “unreasonable searches and seizures” applies when people have a “reasonable expectation of privacy,” continues to shape Fourth Amendment rulings six decades later. That was clear on June 29, when the Court decided Chatrie v. United States, holding that a government-ordered analysis of cellphone location data qualifies as a “search” under the Fourth Amendment.

“An individual has a reasonable expectation of privacy in records about his cell phone’s location, and police intrude on that constitutionally protected interest when they demand the information,” Justice Elena Kagan wrote in an opinion joined by four of her colleagues. Justice Neil Gorsuch agreed with the result but not the rationale. The Katz test, he complained, “has no basis in the Constitution’s text or history.” He added that it has proven unworkable in practice because it has never been clear how courts should determine whether an expectation of privacy is “reasonable.”

Gorsuch is surely right that the Katz test has produced inconsistent and puzzling results. In cases addressing intrusions such as trash searches, demands for bank and telephone records, surveillance by low-flying aircraft, and police trespassing on private property, the Supreme Court has perceived no expectations of privacy it was prepared to recognize as reasonable. Applying the same test, it has repeatedly ruled that the Fourth Amendment does not apply to information that people voluntarily share with third parties. Yet the Court has repeatedly rebelled at the disturbing implications of that principle without explicitly renouncing it.

That is what happened in Chatrie, which involved a Virginia bank robbery investigation. Police used a “geofence” warrant to identify the perpetrator by requiring Google to search customer data collected by its Location History feature, which tracks the whereabouts of cellphone users. For reasons that are not entirely clear, the Court declined to apply the third-party doctrine, instead reverting to the original, unmodified Katz test.

A better approach, Gorsuch argued, would be to treat Location History records as “effects” covered by the Fourth Amendment—as a form of personal property, in other words. While it is not clear exactly how that property-rights approach would work in other contexts, it does seem less malleable than the Katz test, which gives courts wide discretion in discerning expectations and deciding whether they are reasonable. Gorsuch aptly likened the Court’s understanding of that test to its definition of obscenity in the 1960s: “We know a ‘reasonable expectation of privacy’ (and an exception to the third party doctrine) when we see it.”

The Roots of the ‘Reasonable Expectation’ Test

To understand why the object of Gorsuch’s ire seemed like a good idea at the time, it helps to review the facts of Katz’s case. The bookie, who had an apartment on Sunset Boulevard in Los Angeles that the Associated Press described as “expensive,” would often conduct his business from one of three telephone booths near his building, which proved to be his downfall.

After FBI agents “got wind of Katz’s activities and set out to arrest him,” Schneider says, they devised “a rather elaborate plan to do so.” First, “the agents obtained the telephone
company’s consent to put one of the telephone booths out of order.” Then they attached microphones to the roofs of the other two booths. The microphones, which were wired to a recorder on top of one booth, captured Katz’s voice as he made calls to Boston and Miami, relaying bets on basketball games, including contests pitting Duquesne University against St. Bonaventure College and Temple against Lafayette.

Katz’s phone calls violated 18 USC 1084, which made it a federal crime for someone “engaged in the business of betting or wagering” to transmit wagers on sporting events or information facilitating such bets “in interstate or foreign commerce” via a “wire communication facility.” A federal judge in Los Angeles convicted Katz of eight counts and imposed a $300 fine—about $3,200 today.

On appeal, Katz argued that the evidence collected by the FBI’s recorder should have been suppressed because the Fourth Amendment requires a warrant for such eavesdropping. He relied on Silverman v. United States, a 1961 Supreme Court case that also involved a gambling investigation. To verify their suspicions that a row house was “the headquarters of a gambling operation,” District of Columbia police officers drove a “spike mike” into the wall of an adjoining house with the owner’s permission. The microphone made contact with a heating duct in the suspects’ house, enabling the cops to overhear their conversations.

“The eavesdropping was accomplished by means of an unauthorized physical penetration into the premises occupied by the petitioners,” Justice Potter Stewart wrote in the majority opinion. “Eavesdropping accomplished by means of such a physical intrusion is beyond the pale of even those decisions in which a closely divided Court has held that eavesdropping accomplished by other electronic means did not amount to an invasion of Fourth Amendment rights.”

One of the precedents Stewart had in mind was Olmstead v. United States, a 1928 case in which the Court concluded that wiretapping did not implicate the Fourth Amendment. Another relevant decision was the Court’s 1942 ruling in Goldman v. United States, which held that federal agents did not violate the Fourth Amendment when they eavesdropped on the conversations of criminal suspects by placing a “detectaphone” against the wall of an adjoining room. Stewart saw an important difference between remote wiretapping or listening through a wall and poking a microphone into a suspect’s property.

Unfortunately for Katz, the U.S. Court of Appeals for the 9th Circuit thought the FBI’s eavesdropping on him more closely resembled the facts of Goldman. “There was no physical penetration inside of the booths,” the 9th Circuit noted when it rejected Katz’s appeal in November 1966.

A year later in Katz v. United States, the Supreme Court deemed that detail irrelevant. Writing for the majority, Stewart said “the underpinnings of Olmstead and Goldman have been so eroded by our subsequent decisions that the ‘trespass’ doctrine there enunciated can no longer be regarded as controlling.” The main point, Stewart said, was that the FBI had “violated the privacy upon which [Katz] justifiably relied while using the telephone booth.” In other words, Justice John Marshall Harlan II said in a concurring opinion, the Fourth Amendment applies when someone has an “expectation of privacy” that “society is prepared to recognize as ‘reasonable.'”

‘The Limits of Katz‘s Reach’

When it sided with Katz, the Supreme Court said the Fourth Amendment’s scope “cannot turn upon the presence or absence of a physical intrusion into any given enclosure,” rejecting the premise that had led the Court to approve warrantless wiretapping four decades earlier. For anyone concerned about government snooping, that was surely a good result. But subsequent decisions showed the new test was an unreliable safeguard against police invasions of privacy.

“If Katz ushered in a revolution in Fourth Amendment doctrine, the Court was quick to cabin its impact,” Justice Samuel Alito noted in his Chatrie dissent. “Indeed, the Court spent much of the 20th century emphasizing the limits of Katz‘s reach.”

Contrary to what you might expect (perhaps unreasonably), the new standard had no effect on a sweeping exception to the Fourth Amendment that the Court had announced more than 40 years before Katz. “The special protection accorded by the Fourth Amendment to the people in their ‘persons, houses, papers and effects,’ is not extended to the open fields,” Justice Oliver Wendell Holmes Jr. wrote for a unanimous Court in the 1924 case Hester v. United States, approving a warrantless search that had resulted in a South Carolina moonshiner’s arrest and conviction. “The distinction between the latter and the house is as old as the common law.”

Holmes was wrong about that. As Institute for Justice attorneys Robert Frommer and Anthony Sanders noted in a 2017 Supreme Court brief, Holmes misconstrued a discussion of burglary in William Blackstone’s Commentaries on the Laws of England, erroneously thinking it justified the supposedly longstanding distinction he perceived. But despite the shaky basis for the “open fields” doctrine, the Court upheld it under the Katz test in the 1984 case Oliver v. United States, which involved a marijuana farm discovered by Kentucky state police.

“In the case of open fields, the general rights of property protected by the common law of trespass have little or no relevance to the applicability of the Fourth Amendment,” Justice Lewis F. Powell Jr. wrote in the majority opinion. Although the marijuana growers “erected fences and ‘No Trespassing’ signs around the property,” the Court rejected “the suggestion that steps taken to protect privacy establish that expectations of privacy in an open field are legitimate.”

The implication was that “open fields” need not actually be open. Even when private property is fenced and marked with “No Trespassing” signs, the Court said, “no expectation of privacy legitimately attaches to open fields.” At the same time, it acknowledged that the Fourth Amendment does apply to “the ‘curtilage,’ the land immediately surrounding and associated with the home.”

Under the “open fields” doctrine, the Supreme Court ruled three years later in United States v. Dunn, federal drug agents likewise did not need a warrant to approach a barn located about 50 yards from a home on a West Texas ranch, even though they had to cross several fences on the way. Nor did they need a warrant to peer into the barn, where they ultimately found a laboratory producing the methamphetamine precursor phenylacetone, because at that point they were still located in “open fields.” In an opinion by Byron White, who had concurred in Katz, the majority concluded that “the barn and the area around it lay outside the curtilage of the house.”

Oliver and Dunn exemplified the Court’s eagerness to facilitate the war on drugs by whittling away at the Fourth Amendment. Many of those cases explicitly or implicitly involved the Katz test, which often proved no barrier to nosy drug warriors.

In the 1983 case United States v. Knotts, the Court approved the warrantless use of a surreptitiously placed radio transmitter to track a suspected drug trafficker’s car. “A person traveling in an automobile on public thoroughfares,” Justice William Rehnquist said in the majority opinion, “has no reasonable expectation of privacy in his movements from one place to another.”

Three years later in California v. Ciraolo, the Court approved warrantless surveillance by an airplane flying 1,000 feet above a backyard marijuana plot. Even though that area was “within the curtilage” of the home and shielded from ground-level observation by two fences, Chief Justice Warren Burger said in the majority opinion, any expectation that it would be safe from aerial observation was not reasonable. The Court extended that logic in the 1989 case Florida v. Riley, holding that sheriff’s deputies did not violate the Fourth Amendment when they observed a marijuana grower’s greenhouse from a helicopter 400 feet above his property.

Police also are free to search your trash without a warrant, the Court said in the 1988 case California v. Greenwood, because “society” is not “prepared to accept” any expectation of privacy in “garbage bags left at the curb” as reasonable. Suspected Laguna Beach drug dealer Billy Greenwood and his associates “exposed their garbage to the public sufficiently to defeat their claim to Fourth Amendment protection,” White explained in the majority opinion. “It is common knowledge that plastic garbage bags left on or at the side of a public street are readily accessible to animals, children, scavengers, snoops, and other members of the public.”

According to the Supreme Court, police likewise do not need a warrant, probable cause, or even reasonable suspicion to deploy drug-detecting dogs at an airport or during a routine traffic stop. People do not have a “legitimate” expectation of privacy in whatever contraband they may be carrying in their luggage, the Court explained in the 1983 case United States v. Place. And when a police dog sniffs a car that has been legally stopped, according to the Court’s 2005 decision in Illinois v. Caballes, “any intrusion on respondent’s privacy expectations does not rise to the level of a constitutionally cognizable infringement.”

These assurances ring hollow for two reasons. First, canine inspections trigger full-blown searches. Second, they frequently deliver false positives. The Court has said an “alert” by a properly trained dog is enough to provide probable cause for a search, notwithstanding substantial evidence that such alerts are often erroneous, imagined, invented, or triggered by the handler’s subconscious cues. In practice, these rulings mean that a cop with a dog can search cars at will, a situation that hardly seems consistent with reasonable expectations of privacy.

When police saw people bagging cocaine while peering through a gap in an apartment’s closed window blind, the Court said in the 1998 case Minnesota v. Carter, they did not violate a reasonable expectation of privacy because the suspects were not “overnight social guests.” And when police searched a car because they suspected the driver was a drug user, according to the Court’s 1999 ruling in Wyoming v. Houghton, they also were allowed to search a passenger’s purse, since “passengers, no less than drivers, possess a reduced expectation of privacy with regard to the property that they transport in cars.”

The Birth of the Third-Party Doctrine

The war on illegal liquor, which gave birth to the “open fields” doctrine, also figured in the case that inspired the third-party doctrine. After discovering an unlicensed whiskey distillery in 1973, sheriff’s deputies in Houston County, Georgia, connected the operation to Mitch Miller by going through his bank records, which they obtained with a grand jury subpoena rather than a warrant. That was fine, the Supreme Court said in the 1976 case United States v. Miller.

“All of the documents obtained, including financial statements and deposit slips, contain only information voluntarily conveyed to the banks and exposed to their employees in the ordinary course of business,” Powell noted in the majority opinion. “The depositor takes the risk, in revealing his affairs to another, that the information will be conveyed by that person to the Government.”

Miller therefore had no “legitimate expectation of privacy concerning the information kept in bank records,” Powell wrote. More generally, he said, “the Fourth Amendment does not prohibit the obtaining of information revealed to a third party and conveyed by him to Government authorities, even if the information is revealed on the assumption that it will be used only for a limited purpose and the confidence placed in the third party will not be betrayed.”

The Court reaffirmed that principle in the 1979 case Smith v. Maryland, which involved a robbery investigation in which police used a “pen register” to record the numbers dialed from the suspect’s home. “A person has no legitimate expectation of privacy in information he voluntarily turns over to third parties,” Justice Harry Blackmun wrote in the majority opinion.

That doctrine was troubling enough when records were kept on paper in filing cabinets. It is even more worrisome now that Americans routinely entrust vast amounts of sensitive electronic information to third parties.

The Supreme Court confronted that issue in a 2018 case involving cellphone location information collected by cell sites, which the FBI had obtained while investigating a series of robberies in Detroit. Timothy Carpenter, who was convicted based on that information, argued that the FBI’s acquisition of his cell-site data was a “search” under the Fourth Amendment. The Supreme Court agreed, notwithstanding the third-party doctrine.

“While the third-party doctrine applies to telephone numbers and bank records, it is not clear whether its logic extends to the qualitatively different category of cell-site records,” Chief Justice John Roberts wrote for the majority in Carpenter v. United States. “After all, when Smith was decided in 1979, few could have imagined a society in which a phone goes wherever its owner goes, conveying to the wireless carrier not just dialed digits, but a detailed and comprehensive record of the person’s movements.”

In addition to revealing more than the bank and telephone records at issue in Smith and Miller, Roberts argued, “cell phone location information is not truly ‘shared’ as one normally understands the term,” since it is automatically generated by devices that nearly everyone routinely carries. In light of those differences, he said, “we decline to extend Smith and Miller to cover these novel circumstances. 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.”

‘What’s Left of the Fourth Amendment?’

Gorsuch dissented in Carpenter, mainly to express his exasperation at the consequences of the Katz test and the third-party exception. According to Smith and Miller, “the Constitution does nothing to limit investigators from searching records you’ve entrusted to your bank, accountant, and maybe even your doctor,” he wrote. “What’s left of the Fourth Amendment?”

Nowadays, Gorsuch noted, “we use the Internet to do most everything. Smartphones make it easy to keep a calendar, correspond with friends, make calls, conduct banking, and even watch the game. Countless Internet companies maintain records about us and, increasingly, for us. Even our most private documents—those that, in other eras, we would have locked safely in a desk drawer or destroyed—now reside on third party servers.”

Under the third-party doctrine, “police can review all of this material, on the theory that no one reasonably expects any of it will be kept private,” Gorsuch wrote. “But no one believes that.”

The Supreme Court “has never offered a persuasive justification” for the third-party doctrine, Gorsuch said. “The fact that a third party has access to or possession of your papers and effects does not necessarily eliminate your interest in them. Ever hand a private document to a friend to be returned? Toss your keys to a valet at a restaurant? Ask your neighbor to look after your dog while you travel? You would not expect the friend to share the document with others; the valet to lend your car to his buddy; or the neighbor to put Fido up for adoption.”

As Gorsuch saw it, the problem began with the Katz test itself. “We still don’t even know what its ‘reasonable expectation of privacy’ test is,” he wrote. “Is it supposed to pose an empirical question (what privacy expectations do people actually have) or a normative one (what expectations should they have)?” Either way, he said, the courts generally are not qualified to supply the answers.

Because of its subjectivity, the Katz test “has yielded an often unpredictable—and sometimes unbelievable—jurisprudence,” Gorsuch added. According to the Supreme Court, “a police helicopter hovering 400 feet above a person’s property invades no reasonable expectation of privacy,” he noted. “Try that one out on your neighbors.”

Gorsuch also mocked the Court’s logic in upholding warrantless trash searches. “The habits of raccoons don’t prove much about the habits of the country,” he wrote. “I doubt, too, that most people spotting a neighbor rummaging through their garbage would think they lacked reasonable grounds to confront the rummager. Making the decision all the stranger, California state law expressly protected a homeowner’s property rights in discarded trash.”

Gorsuch proposed an alternative to the Katz test. “The Fourth Amendment protects ‘the right of the people to be secure in their persons, houses, papers and effects, against unreasonable searches and seizures,'” he noted. “True to those words and their original understanding, the traditional approach asked if a house, paper or effect was yours under law. No more was needed to trigger the Fourth Amendment.”

When courts apply that property-rights test, Gorsuch suggested, “positive law may help provide detailed guidance on evolving technologies without resort to judicial intuition,” since state or federal law “often creates rights in both tangible and intangible things.” The states and the federal government “are actively legislating in the area of third party data storage and the rights users enjoy,” he noted. “State courts are busy expounding common law property principles in this area as well. If state legislators or state courts say that a digital record has the attributes that normally make something property, that may supply a sounder basis for judicial decisionmaking than judicial guesswork about societal expectations.”

Cellphone Location Data As ‘Personal Property’

Something similar happened in Chatrie. That case also involved cellphone location data obtained as part of a robbery investigation, although it was different in two notable ways: Google’s Location History information is more precise and comprehensive than the cell-site data at issue in Carpenter, and the company’s initial search involved analyzing the records of some 500 million customers, as opposed to specific accounts that had already been identified.

If anything, those differences magnified the privacy concerns raised by Chatrie, so it is not surprising that the Court thought the Fourth Amendment was relevant. But Kagan’s explanation for declining to apply the third-party doctrine, which reiterated Roberts’ rationale in Carpenter, still seemed dubious, especially when it came to the question of whether cellphone users “truly” share their location information.

The government argued that they do in the case of the Location History feature, since it is “an optional add-on.” Rebutting that argument, Kagan noted that Google repeatedly prompts users to activate that feature, often warning that their Android phones will not “work correctly” without it. Whatever you make of that dispute, it seems clear that people voluntarily share information with third parties when they send email, visit websites, use social media, or store photos, videos, and documents on remote servers. The question is why those choices should be viewed as constitutionally relevant.

This time, Gorsuch concurred, but only in the judgment. In addition to reiterating his critique of Katz and the third-party doctrine, he elaborated on how his property-rights approach can be applied to remotely stored data.

“Based on the evidence the parties have put before us, it appears the word ‘effects’ was understood at the time of the Fourth Amendment’s adoption to embrace most any kind of personal property,” Gorsuch wrote. He cited several pieces of evidence suggesting that a cellphone user’s Location History information qualifies as his property.

“As Google puts it, and no one seriously disputes, Location History serves as a ‘diary’ or map ‘of a person’s travels,” Gorsuch said. At the time of the investigation at issue in Chatrie, he noted, Google’s agreement with cellphone users “referred to Location History as ‘your’ (meaning, the user’s) ‘information.'” The agreement allowed each user to “review” and “edit” his location data or even “export or delete that data ‘from Google’s servers at will.'” Google promised to protect the information from “unauthorized access, alteration, disclosure, or destruction.”

In short, Gorsuch wrote, the Virginia robbery defendant who brought this case, Okello Chatrie, “had the rights to enjoy, manage, alter, dispose, and exclude others from what amounted to an electronic diary or map of his travels. And as someone who held that many ‘sticks in the bundle of rights…commonly characterized as property’—including the ‘most treasured’ and ‘essential’ right to exclude—he has a strong claim that the Location History data was his personal property.”

Gorsuch also noted the treatment of such information under Virginia law. “That State’s Computer Crimes Act expressly describes ‘computer data’ as a form of ‘[p]roperty,'” he wrote. “Altering or making an unauthorized copy of computer data can constitute the crime of ‘computer trespass’ (another property law concept). And the State provides a right to sue for anyone ‘whose property or person is injured’ by violations of the Act (again suggesting a right to exclude).”

Virginia is not unusual in these respects. Most states “have enacted or amended laws to treat digital records and data as personal property,” the Cato Institute’s brief in Chatrie noted. “Many of these laws make it illegal for private actors to access or convert another person’s digital data. By explicitly defining digital records as ‘property’ and by enacting digital privacy statutes that give users the right to obtain, control, and delete their personal information, states have recognized that users often own their digital records.”

At the time of the robbery investigation, Google stored Location History data on its own servers. But from a property-rights perspective, the fact that Chatrie entrusted his data to Google for certain purposes is not decisive.

“An individual need not have ‘complete ownership or exclusive control’ before he can assert a Fourth Amendment challenge against the search of real property,” Gorsuch noted. The Court has “long recognized” that tenants and family members have Fourth Amendment rights with respect to the places where they live, he said, and “I fail to see why the law should differ markedly when it comes to personal property.”

When you “[t]oss your keys to a valet at a restaurant” or “[a]sk your neighbor to look after your dog while you travel,” Gorsuch noted, “you may entrust your personal property to another and license him to do certain things with it, much as Mr. Chatrie did with his Location History data. But that hardly means that property is no longer yours.”

Nor does it matter, in Gorsuch’s view, that the Framers “might not have imagined an electronic diary or map of one’s travels,” since “the terms found in the Fourth Amendment carry their original public meaning and can bear more applications than its drafters might have expected or intended.” Just as the First Amendment “protects speech over the internet today no less than it did speech delivered in the town square in 1791,” he said, “it should hardly come as a surprise that the Fourth Amendment might protect as personal ‘effects’ electronic diaries of one’s travels as it always has more traditional ones.”

The Continuing Relevance of Property Rights

Katz did not make property rights irrelevant in Fourth Amendment cases. In the 2012 case United States v. Jones, for example, the Court held that police needed a warrant before attaching a GPS tracking device to a drug suspect’s car, emphasizing the physical trespass that entailed. Writing for the majority, Justice Antonin Scalia noted that Katz “did not repudiate” the understanding that the Fourth Amendment reflects a particular concern about “government trespass” on people and their property.

As Gorsuch concedes, there is some overlap between the Katz test and the approach he favors. Judges sometimes “may be able to discern and describe existing societal norms,” Gorsuch wrote in Carpenter. In the 2013 case Florida v. Jardines, for instance, Scalia noted that people generally are free to approach the front door of a home without advance permission, a tradition that reflects “the habits of the country.” But that general license, Scalia said in the majority opinion, does not mean police are free to deploy a drug-detecting dog at someone’s doorstep, which is indisputably within the specially protected “curtilage.”

The identification of “reasonable expectations” may be defensible when it relies on “positive law rather than intuition for guidance on social norms,” Gorsuch said. As an example, he cited Byrd v. United States, a 2018 case in which the Supreme Court held that a driver can have a reasonable expectation of privacy in a rental car even if he is not listed on the rental agreement. In reaching that conclusion, Gorsuch noted, the unanimous Court relied on “general property-based concept[s].”

In such cases, Gorsuch said, the Katz test “may simply wind up approximating” the results of a property-focused analysis. In Chatrie, the majority likewise alluded to property rights while asking about reasonable expectations of privacy. “Location History resembles other private materials—think of emails, documents, photographs, or calendars—that even if stored on Google’s servers, a user reasonably views as his own,” Kagan wrote. “Put another way,” Gorsuch  remarked, those things “are his effects.”

Harlan’s concurrence in Katz also implicitly relied on property rights. “The critical fact in this case,” he said, is that someone who “occupies” a telephone booth, “shuts the door behind him,” and “pays the toll that permits him to place a call” is “surely entitled to assume” that “his conversation is not being intercepted.” That situation, where someone expects privacy because he has paid to use an enclosed space, is analogous to a hotel room or a rented apartment, where occupants have legally recognized privacy rights even though they do not hold the deed to the property.

A “reasonable expectation” test grounded in property rights, as reflected in statutes, contracts, and the common law, would be essentially the same as the approach that Gorsuch proposes. It would go beyond the physical intrusions that the Supreme Court emphasized prior to Katz, since it would take into account evidence such as user agreements, state laws, and court decisions recognizing property rights in “intangible things,” even when they are stored on third-party servers. At the same time, that approach would constrain the “judicial guesswork” that Gorsuch believes has frequently led the Court astray.

Whether couched as a revised Katz test or a return to a “more traditional” understanding of the Fourth Amendment, as Gorsuch describes it, a property-focused analysis would not authorize a broad exception for information shared with third parties. Carpenter and Chatrie suggest that the justices are beginning to recognize the alarming implications of that doctrine.