Fourth Amendment

Reconciling Katz and the Fourth Amendment Text

Some people think the Katz "reasonable expectation of privacy" test is hard to reconcile with the text of the Fourth Amendment. Here's why I think they're wrong.


Monday was the 50th Anniversary of Katz v. United States, the Supreme Court's big decision on the Fourth Amendment's "search" test. I often hear that Katz created a vague and non-textual notion of "privacy" that is unmoored from the text. But it seems to me that it's easy to reconcile Katz with the text of the Fourth Amendment. To be sure, Katz was decided in an era when text and history wasn't particularly important. If you follow what opinions say on their face, rather what they actually do, Katz seems weirdly inattentive to the text. But if you focus on what the Katz framework actually does, it seems to me, the decision is readily reconcilable with the text.

This post will explain why.

Let's start, appropriately enough, with the text:

The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

The second part of that, often called the warrant clause, is pretty narrowly about search warrants. So it's the first part that matters more broadly. That first clause of the text recognizes a right of the people against "unreasonable searches and seizures" in "their persons, houses, papers, and effects."

If you're a textualist, you would break down the Fourth Amendment text into four questions:

(1) Is the thing to be protected a "person, house, paper or effect"?

(2) If the answer is yes to (1) above, is it the person, house, paper or effect of the individual claiming the constitutional violation (that is, is it "their" person, house, paper or effect or someone else's)?

(3) If the answer is yes to (2) above, was the individual's person, hour, paper or effect "searched" and/or "seized"?

(4) If the answer is yes to (3) above, was the search and/or seizure "unreasonable"?

So that's the text. If you follow Fourth Amendment doctrine, you know that it tends to combine Questions 1, 2, and 3 into a single question: Was the government action a search or seizure? And then the Katz test for a what is a search, from Justice Harlan's concurring opinion in Katz, is often expressed as a two-part test: First, did the person exhibit a subjective expectation of privacy? Second, if so, was that expectation of privacy an expectation that society is prepared to accept as reasonable?

At first blush the Katz test might seem contrary to the text, or at least not particularly related to it.

But here's the thing: It's pretty easy to restate the Katz test using the constitutional text. The reason is that Katz preserved all four textual questions. At times it used non-textual labels for their concepts. But Katz uses the same concepts that you encounter based on a close reading of text.

Recall the facts of Katz. The FBI taped a microphone to the top of a public phone booth Katz used to place illegal bets. When Katz went into the phone booth, closed the door, and paid for the call, the FBI turned on the microphone and recorded his side of the call. In his concurrence, later adopted by the Court, Justice Harlan identified the three major holdings of the majority opinion:

I join the opinion of the Court, which I read to hold only (a) that an enclosed telephone booth is an area where, like a home, Weeks v. United States, 232 U. S. 383, and unlike a field, Hester v. United States, 265 U. S. 57, a person has a constitutionally protected reasonable expectation of privacy; (b) that electronic as well as physical intrusion into a place that is in this sense private may constitute a violation of the Fourth Amendment; and (c) that the invasion of a constitutionally protected area by federal authorities is, as the Court has long held, presumptively unreasonable in the absence of a search warrant.

These three holdings match up with three of the four textual steps. Holding (a), that an enclosed telephone booth is an area protected by the Fourth Amendment, was in textual terms saying that an enclosed telephone booth (like a home but unlike an open field) was a Fourth Amendment "effect." That is, it was answering Question 1, identifying the spaces or things protected by the Fourth Amendment.

Holding (b), that electronic as well as physical intrusion can violate the Fourth Amendment, was in textual terms saying that an electronic intrusion can be a "search" of the Fourth Amendment "effect" of the phone booth. It was answering Queston 3, whether the effect was searched or seized. And holding (c), that a warrant was required, was in textual terms (as Justice Harlan recognized) saying that a search or seizure is unreasonable without a warrant. That's obviously the Queston 4 reasonableness iquiry

The only step explicitly missing in Harlan's summary of Katz's holding was the Question 2 inquiry into whether the search that occurred was of Mr. Katz's own effects or someone else's effects. But that was made clear in the majority opinion, in what Justice Harlan called the "critical" point of the majority opinion: It was "a person in a telephone booth" who "may rely upon the protection of the Fourth Amendment." As Justice Stewart wrote for the majority:

One who occupies it, shuts the door behind him, and pays the toll that permits him to place a call is surely entitled to assume that the words he utters into the mouthpiece will not be broadcast to the world.

Katz, 389 352. In Justice Harlan's words, during that time the phone booth became a "temporarily private place" for the caller. This is the Question 2 point. The phone booth was not just an "effect" in the abstract, but it was the constitutional "effect" of the person who occupied the phone booth and paid the toll during the period of the call.

The upshot of all of this is that we can pretty easily interpret Katz using the constitutional text. In textual terms, Katz held that the phone booth was an "effect" that the Constitution protects (Question 1); that when callers occupy the booth and pay the toll, the phone booth becomes "their" effect (Question 2); that listening in from a microphone taped to the top of the phone booth was a "search" of that effect (Question 3); and that the search of their effect was "unreasonable" without a warrant (Question 4).

But wait, you may be wondering, what about Justice Black's dissent? Justice Black dissented on textualist grounds, after all. But he did so on a really narrow point. Justice Black focused on the use of the recording device instead of its installation. In his view, turning on the microphone to capture Katz's voice was not a "search" or "seizure" of any "persons, houses, papers, and effects." Here's the key passage:

The first clause protects "persons, houses, papers, and effects against unreasonable searches and seizures. . . ." These words connote the idea of tangible things with size, form, and weight, things capable of being searched, seized, or both. The second clause of the Amendment still further establishes its Framers' purpose to limit its protection to tangible things by providing that no warrants shall issue but those "particularly describing the place to be searched, and the persons or things to be seized." A conversation overheard by eavesdropping, whether by plain snooping or wiretapping, is not tangible and, under the normally accepted meanings of the words, can neither be searched nor seized.

Note that Justice Black assumed that the "persons, houses, papers, and effects" had to be the conversation that was recorded, not the phone booth. The overheard conversation wasn't a person, house, paper, or effect, so to Justice Black it made no sense to say that eavesdropping was protected by the Fourth Amendment. But as far as I can tell, Justice Black never addressed the more obvious textual basis for the majority's decision: That the phone booth was the "efffect," and that the installation and use of the microphone was the "search" of that effect. From that perspective Katz was something like United States v. Jones, the GPS case, in which the majority concludes that installing the device was a "search" of the "effect" that was the car Jones drove while the concurring opinions focus on use of the GPS device to collect location information.

Now some of you may be reading this long post and thinking, how do you deal with the "reasonable expectation of privacy" test? From a textual perspective, I think that test is best understood as just a way to express when a person's "effects" are "searched." A person has a reasonable expectation of privacy in a place or thing when that thing is the person's "effect" (or their house, person, or papers, of course, but that is usually an easier case). When government action infringes that reasonable expectation of privacy, that effect is "searched," at least unless a person reveals that place or thing to others and therefore gives an implied license to search it (which you can equivalently see as not manifesting a subjective expectation of privacy or else as an implied license under Florida v. Jardines).

If it seems nontextual to rely on a vague phrase like "reasonable expectation of privacy" to identify what counts as a "search" of an "effect," it helps to recall a bit of Fourth Amendment history. As I detailed in The Curious History of Fourth Amendment Searches, courts before Katz really struggled to say what counted as a search. The early cases on the meaning of "searches" used an uncertain mix of privacy concepts and analogies to property without ever stating a particular test for what made something a search. Indeed, as far as I can tell, the first effort to articulate what makes something a search was Justice Harlan's effort to summarize "the rule that has emerged from prior decisions" in his Katz concurrence. This was the so-called "Katz test" that focuses on expectations of privacy.

But Justice Harlan's test was not designed to make vague notions of privacy the core of the Fourth Amendment, it seems to me. It is true that the test Justice Harlan articulated included the word "privacy." But I think Justice Harlan had something more specific in mind. The puzzle in Katz was which kinds of spaces could receive Fourth Amendment protection from searches. Homes, taxicabs, and rented hotel rooms could, the precedents indicated. Open fields could not. The specific question in Katz, as articulated by Justice Harlan at the beginning of his concurrence, was how to treat a phone call inside a public phone booth with glass walls and a door. Was that more like a rented hotel room (protectable) or an open field (not protectable)?

As I understand Harlan, the idea of what expectations "society is prepared to recognize as reasonable" was not some sort of free-floating notion but rather a more specific idea. Some places were treated like the home and others were not. How do you determine what is treated like the home? What's the line? It wasn't the common law of property, a standard that the Court had never embraced and indeed had long ago rather harshly dismissed. Rather, it was an idea that some places were broadly understood by people as home-like. And that was the case with a public phone booth in Katz. When a person entered the booth, shut the door, and paid for their call, the booth became understood as their booth for the duration of the call. It was therefore protectable under the Fourth Amendment.

From this perspective, Justice Harlan's test could be readily articulated using the Fourth Amendment text. The reasonable expectation of privacy test is just asking if the government action is a search of the individual's "person, houses, papers, or effects." The idea of what "society is prepared to recognize" really goes to what is considered a person's "effects." A public phone booth was among the caller's "effects" during the call; it was a temporarily rented space that became theirs for that brief time window.

This view also explains why the move to a trespass-property view of "searches" in Jones doesn't make much (if any) difference to what the Fourth Amendment protects. It changes the black-letter law a lot. But as I discussed in Curious History, it's not clear what if any results it changes. The Katz framework is best understood as doing the same work that an explicitly textual approach does. It uses different words, yes. But properly understood, it seems to me, it's doing the same basic work.

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  1. I can’t say I’ve researched a definition of “effects” but I would imagine that is the textualist issue. The reasonable expectation of privacy test bears no resemblance to a textual definition of “effects.” So while you can frame it that way it doesn’t really reconcile it with the text.

  2. So the Katz decision turned in part on the rationale that a caller in a phone booth who closes the door and places a phone call has created a temporary “effect” in which he is entitled to expect privacy.

    It is interesting that in the decades following the Katz decision, phone booths were phased out and replaced with public phones attached to the wall in open public space. Would it be paranoid of me to wonder whether the phone companies were “encouraged” by the government to phase out phone booths as a means of circumventing the Katz decision? Interesting question.

  3. I suggest that if the purpose of the Amendment is to protect privacy, it’s just badly written: “unreasonable” is a weasel-word, pure and simple, and means whatever the government can convince a sympathetic judge it does. Rather than debate whether the angels are doing a schottische or a contra-dance in the head of that pin, why not propose a new Amendment that will do the job?

    1. Or just privacy statutes. We control the actors that the 4A is intended to bind.

  4. I always read Katz as focusing on the “persons,” rather than “effects,” part of the Fourth Amendment. The opinion specifically says that the issue does not depend on the categorization of the phone booth. And I’m not sure I agree with the suggestion that the right against searches depends entirely on some form of property interest. Would Katz have been unprotected if he hacked the phone rather than paying to use it?

    “Persons, houses, papers, and effects” is pretty broad, and arguably the inclusion of “persons” means that information gained from a person is protected as long as the information is gained through a “search.” If the information is not taken directly off the person, then the 4th Amendment only applies to “houses, papers, and effects.” In Katz, the information at issue was taken directly off Katz’s “person,” so I don’t think an effects analysis is necessary. The question is whether the information was taken by a “search.”

    Most of the rest of Fourth Amendment law seems to me like an “assumption of the risk” analysis. We assume the risk that the public is watching us drive, but not that they put a trespassory device on our car. We assume the risk that someone is watching our house from the road, but not that they are doing so with a thermal imaging device. We assume the risk that people we are talking to will record us, but not that a third party is wiretapping our phone. That goes to whether something is a “search,” not to whether it is a protected “effect,” etc.

    1. “We assume the risk that the public is watching us drive, but not that they put a trespassory device on our car.”

      So if I purchase a phone subject to an agreement where the phone company promises to put a trespassory device on the phone, have I assumed the risk that the third-party is, in fact, following me around?

  5. Professor,

    To address your point regarding Justice Black and his failure to address the effect, isn’t Katz also about an intersection of third party doctrine and REOP? As I understood his point, Justice Black wasn’t really looking at the phone booth itself, because the device was outside. Thus, who cares whether the booth itself was protected, because the conversation was not. His logic would equally apply, I think, to listening to phone conversations wherever they originated. In contrast, the Majority said it did not matter that the device did not happen to penetrate the wall of the booth; Katz had REOP that the Government is not listening in on his conversations.

    Compare Katz to a case like Hoffa v. United States, where a Government informer went to Hoffa’s hotel and listened to his conversations. You don’t have any privacy rights in what you voluntarily disclose to others. Take disclosure to its extreme: when you start speaking to anyone, government agent or not, the Government is free to listen. Katz says no to that, which is why, I think, it is significant that the device was outside the booth.

    I think people implicitly accept there’s no REOP in what is said to another person, and they can go ahead and tell others what I said (if not record what I am saying, depending on whether the State in question is one-party or two-party consent). However, the unspoken assumption is that I have some sort of control in who hears the substance of those conversations.

    1. (Reply since I exceeded comment limit)

      Here’s a hypo: As I recall, the book 1984 included the government installing microphones in literal fields in the countryside, which is how they overheard Winston’s conversations. Could the government install microphones in open fields to capture what we say, under a disclosure theory? (I’d have to reread Jones, but my guess is if the open field in question is part of my property a trespass rationale would apply to the installation of such a device, but as to public fields, the question changes).

      1. Unless state law bars it, yes, they can install surveillance equipment in (or overlooking) open fields, or fly over open fields. See Oliver v. US for why trespass (at common law, since we’re ignoring state law) isn’t a relevant consideration.

        (I’m not aware of any appellate decision on surveillance equipment in open fields, but it’s come up in District Courts, which consistently allow it under 4A.)

    2. “…isn’t Katz also about an intersection of third party doctrine and REOP?”

      No. Katz has nothing to do with the third party doctrine. If Katz’s co-conspirators had recorded the phone calls and handed them to police, he would have lost.

      1. Yes, I understand that. I didn’t mean directly, I meant implicitly. You don’t have REOP in the content of those conversations, since you voluntarily disclosed it to your coconspirators (and it wouldn’t matter if they were agents of government, as in Hoffa.) I’m saying there’s REOP the government isn’t listening in on your calls even though you’re “disclosing” it to the other parties to your conversation.

        1. I don’t know what you mean. If the government gets the contents of the conversation that you have a REOP in from the other parties to the conversation, no 4A issues.

          1. Im not saying what I mean very well, one of the dangers of commenting on phone and while I do a million things before the holidays.

            I get that 4th A governs how government learns what it learns, not what they learn. What I was trying to convey is I’m not sure an underlying rejection or 3rd party isn’t going on in a case like Katz. If you take the doctrine to its extreme, if I converse on the phone I take the risk someone along the wire (ie a company managing the technology) can listen in whIle im conversing. If that’s true, didn’t Katz lose expectation of privacy while conversing?

            1. “What I was trying to convey is I’m not sure an underlying rejection or 3rd party isn’t going on in a case like Katz.”

              Katz predated Smith. The 3PD is just a long way of saying that Katz (and accordingly the 4A) doesn’t apply because when you share information with a third party, you don’t have a REOP in the information.

              “If you take the doctrine to its extreme, if I converse on the phone I take the risk someone along the wire (ie a company managing the technology) can listen in whIle im conversing.”

              Yes. That’s what Smith v. Maryland says.

  6. Pretty good post that I think well illustrates why Carpenter should prevail. If a public phone booth can be my effect and any conversation flowing out from it is thus protected, certainly my phone and its location dated are protected.

    The idea that 3rd party doctrine pierces the 4th Amendment based on assertions about subjective expectations isn’t convincing. It was known that switchboard operators/neighbors might listen in on a line, but we didn’t develop doctrine based on that observable reality.

    The fact that a third party obtains your information normally obviates your right to complain about a violation, even if obtained without your knowledge or even illegally. This seems to be the Professor’s view of why the government should win.

    But then we consider Black’s reasonable observation that eavesdropping (in a public place) isn’t a search. If the proverbial policeman can sit on a poll for 10 hours (such as to justify placement of a camera), why can’t he sit on a public phone booth and listen? Or consider the government’s reasonable argument in Kyllo that only heat outside of houses was measured. 4th Amendment jurisprudence is full of these reasonable arguments. But the Court recognized something unreasonable was going on.

    The Court grappled with the implications of new technology and didn’t blindly apply doctrine based on different kinds of assumptions, and did it, as the professor explains, in a way that aligns with the text of the 4th Amendment.

    1. “If a public phone booth can be my effect and any conversation flowing out from it is thus protected, certainly my phone and its location dated are protected.”

      This is a perfect example of why this issue is so hard to discuss. You’ve taken a narrow holding (government can’t put a listening device on a phone booth to listen to your conversation) and casually made it broad (all conversations said into a phone are thus protected). You’ve then analogized to a different set of facts (phone and its location are protected). The rub here is “is thus protected”. Protected from what? The government can’t, without a warrant, place a recording device on your iphone. But if Apple volunteers that information to the government, no problem. In Katz, if the person on the other end of the phone recorded it and sent that to the police, no problem. The conversation in Katz was not absolutely protected; the 4A merely limited the manner in which the government could get the contents of the conversation. The 3PD is about how the government gets in the information, not its absolute privilege.

      Same deal with Kyllo. It has nothing to do with 3PD, and somehow it is instructive on what should happen in Carpenter? Why? Because you’ve taken it to a level of generality of “implications of new technology”? Red car/green car.

  7. If you take that sentence at face value isolated from my explanation that follows, then your response makes sense. But clearly I was not making the argument that the dispositive issue here is that we are dealing with a phone.

    You get so snagged on my first sentence that you complicate things!

    Granted, I am reading the precedent broadly while you are reducing it to fairly technical matters. My touchstone here is reasonableness. We can look at Riley (that also happens to involve a phone) where the Court said the search was not reasonable, notwithstanding defensible broad precedent.

    You’re missing the forest for the trees here.

    1. Where third party doctrine is concerned, reasonableness doesn’t even come into play. Because you can’t have a reasonable expectation of privacy in the contents of a conversation with respect to the person you are having the conversation with. That’s true for cell phones, too. If you are voluntarily transmitting data to a person, you can’t simultaneously expect them not to have that information.

  8. How do you square the clause “The right of the people to be secure in their persons, houses, papers, and effects…” with the third party doctrine as applied to cloud storage or email?

    I don’t mean how do you do so as a purely formal matter. Of course you can point out that because it is under the control of the cloud storage provider its not actually a search. But this strikes me as the kind of overly formal approach that is unlike the one we take with the first amendment where we look to the underlying motivations/values being protected when we extend it to a new context.

    In particular, the constitution didn’t include that clause just to create a formal hurdle to jump over but because there was some important societal end served by preventing the government from just walking in and thumbing through people’s papers without a warrant.

    Yet if technology has changed sufficiently so what was once stored as papers in ones house is now as a matter o course uploaded to cloud drives doesn’t that at least suggest that whatever social end the 4th amendment protects is being undermined by the modern application of the 3rd party doctrine?

    1. “Yet if technology has changed sufficiently so what was once stored as papers in ones house is now as a matter o course uploaded to cloud drives doesn’t that at least suggest that whatever social end the 4th amendment protects is being undermined by the modern application of the 3rd party doctrine?”

      Not necessarily. If people instead developed a custom to store all their papers at Tom’s house, and everyone understood that Tom always unlocked his doors, and let the police into his house to thumb through his papers whenever the police came knocking, then people who stored their information at Tom’s wouldn’t be heard to complain about their unreasonable expectation of privacy being violated.

      It depends on which cloud storage system you use. If you use one that routinely hands over information to the government absent a warrant, without asserting their own 4A rights, whatever your expectation of privacy is, it ain’t reasonable. If the cloud storage system administrator is actually a secret government informer, that’s not a 4A issue. The 4A presumes that people who want to keep things secret behave that way.

      1. My point wasn’t to establish that the behavior either should or should not be granted fourth amendment protection but that to determine that question on must have at least some kind of view about what social values the constitution meant to protect with the 4th amendment.

        And no, your example is not so clear. It might be clear as a matter of current precedent but whether or not letting the police search the papers in Toms house without a warrant undermined the social value protected by the 4th amendment depends greatly on what you think that value is.

        If, as perhaps you are suggesting, you think that value is something about avoiding the psychological harm of feeling ones private affairs are being pooked into or the like than sure that’s not a problem.

        On the other hand, if you instead see the 4th amendment as a bulwark against government tyranny and think of the warrant requirement as a means to make sure the government can’t just page through the records of people’s lives on fishing expeditions so they can deter dissent and keep themselves in power then despite people’s knowledge that tom keeps those documents out for anyone to peruse letting the police use that information without a warrant would undermine the ends the 4th is there to protect (on this hypothetical)

        I don’t want a particular outcome here…I was hoping that Professor Kerr would articulate a theory about his view of the intended/appropriate purpose of the 4th amendment.

  9. Would it be fair to say, then, that under the text of the Fourth Amendment, as explicated by Katz, a search is a 1)governmental invasion, of 2)a reasonable expectation of privacy that is 3)closely associated with the person, house(s), papers, or effects, of 3)the person who seeks to complain?

    It seems a bit of a stretch to call the phone booth, even after money is put in to make a call, an “effect” of the caller; it might be argued that the seizure of the conversations is a search of the person. Neither works tremendously well, but probably the best that can be done to reconcile Katz with the text of the amendment.

    Enjoyed your post!

  10. Interesting post. But perhaps the most interesting is that you comment, not on the “opinion” of Katz, which I would take to mean the majority opinion authored by Justice Stewart, but on Justice Harlan’s concurrence, authored by him alone. I realize that the Harlan concurrence has dominated subsequent discussion of the case. But if you’re being textualist about the Constitution, you might also be textualist about the (majority) opinion, too. I think (I’ve actually argued in a law review article) that the majority opinion is much more about regulation than privacy, and the court pushing it’s strong view of the Warrant Clause. In addition, the Court in Katz mirrors its approach in Miranda, by talking about what good cops, meaning the FBI, would do as a measure of why the state procedure falls short.

    Eric J. Miler

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