The Unreasonable Searches and Seizures Clause

The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated . . . .

—Orin S. Kerr

Introduction

The prohibition of unreasonable searches and seizures appears in the Fourth Amendment, ratified in 1791. The clause regulates a vast array of law enforcement practices that include arrests, entries into homes, traffic stops, telephone surveillance, and looking through cell phone records. This essay examines the history of search and seizure before the Revolution, the enactment of the Fourth Amendment, and the development of modern doctrine.

History Before 1789

In mid-eighteenth-century England, a series of abuses by King George III and his representatives led to widespread opposition to general warrants. These court orders authorized government officials to search and seize evidence that placed few, if any, limitations on where the officials could search and what they could seize. Opposition to general warrants found expression in two famous English cases, Entick v. Carrington (1765) and Wilkes v. Wood (1763).¹ Both involved pamphleteers who were critics of the government. They were arrested and their books and papers were seized using general warrants. In Wilkes’s case, the government also seized the papers of forty-nine of his friends. Both men sued the seizing agents for trespass and won judgments in their favor.

In the colonies, leading figures closely watched and cheered on the challenges to general warrants. In 1761, James Otis argued against these warrants in the Writs of Assistance case in Boston with future Founder John Adams in the audience.² Although Otis lost the case, his challenge to general warrants drew significant attention to the threat to civil liberties that general warrants posed. As John Adams later reflected on the oral argument, “Then and there the Child Independence was born.”³

Following the Declaration of Independence, several state constitutions adopted protections focused on general warrants. Some addressed such warrants exclusively. The Virginia Declaration of Rights of 1776, written by George Mason, defined “general warrants” as authorizing “any officer or messenger . . . to search suspected places without evidence of a fact committed, or to seize any person or persons not named, or whose offense is not particularly described and supported by evidence.”⁴ The Declaration stated that such warrants “are grievous and oppressive and ought not to be granted.”

Other state constitutions introduced the notion that there was a broader right against some kinds of searches and seizures, although their texts continued to link the concept to general warrants. The Pennsylvania constitution of 1776 provided that “the people have a right to hold themselves, their houses, papers, and possessions free from search and seizure, and therefore [general] warrants . . . ought not to be granted.”⁵ The Massachusetts constitution of 1780 added a provision, drafted by John Adams, that was the first to articulate a specific right against unreasonable searches and seizures: “Every subject has a right to be secure from all unreasonable searches, and seizures, of his person, his houses, his papers, and all his possessions.”⁶ The provision then linked that right to general warrants, which “are contrary to this right[.]”

Enactment of the Fourth Amendment

During the Virginia convention, Patrick Henry opposed ratification in part on the ground that the Constitution contained no equivalent protections against unreasonable searches and seizures. “Suppose an exciseman will demand leave to enter your cellar, or house, by virtue of his office,” Henry queried. “If Congress be informed of it, will they give you redress?”⁷ In approving the Constitution, a Virginia commission recommended a bill of rights that included a search and seizure provision providing that “every freeman has a right to be secure from all unreasonable searches and seizures of his person, his papers, and property.”⁸

In 1789, during the first Congress, Representative James Madison of Virginia introduced what would eventually become the Fourth Amendment. Madison’s initial proposal was focused on general warrants: “The rights of the people to be secured in their persons; their houses, their papers, and their other property, from all unreasonable searches and seizures, shall not be violated by warrants issued without probable cause, supported by oath or affirmation, or not particularly describing the places to be searched, or the persons or things to be seized.”⁹ The Committee of Eleven, made up of representatives of each state, divided the text into two distinct clauses. The first banned unreasonable searches and seizures: “The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated . . . .” The second specifically banned general warrants: “[N]o 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.” (See Essay No. 167.) Unfortunately, there are no records that might explain why these changes were made. The Fourth Amendment was then ratified by the states without any meaningful debate.

At the time of the Fourth Amendment’s enactment, the nearly exclusive focus was general warrants; little to no attention was paid to the ban on unreasonable searches and seizures. This history makes the original public meaning of the ban on “unreasonable search and seizures” a source of considerable uncertainty. If that term was specifically discussed or its meaning specifically articulated, apart from the ban on general warrants, no records of those discussions are known.

In the absence of clear evidence from the time of its drafting and ratification, scholars have offered different views about the meaning of unreasonable searches and seizures. Professor Thomas Davies argued that the Fourth Amendment was largely focused on abolishing general warrants.¹⁰ In his view, the text of the Fourth Amendment does not impose a more general requirement of reasonable police practices. William Cuddihy argued that the Fourth Amendment was originally understood both to prohibit general warrants and more generally to guard against abusive law enforcement practices.¹¹ Professor Akhil Reed Amar wrote that the Fourth Amendment as originally understood was intended to promote reasonableness in government investigations, not the imposition of a default warrant requirement.¹² Your author has argued that modern Fourth Amendment doctrine is consistent both with the constitutional text and with the original public meaning.¹³

What Is a Seizure?

The threshold question under the Fourth Amendment is whether a government search or seizure has occurred. Under current precedent, a person’s property is “seized” when the government meaningfully interferes with a person’s possessory interest in his property.¹⁴ This occurs when the government takes a suspect’s property from him, forces a person out of his or her home, or takes a package or letter out of the course of delivery.¹⁵ Similarly, a person is “seized” under the Fourth Amendment when the government terminates or restrains his freedom of movement through means intentionally applied.¹⁶ This happens when a government official places a suspect under arrest.¹⁷ A seizure also occurs when the government temporarily detains a person in circumstances in which a reasonable person would not feel free to terminate the encounter and leave.¹⁸

What Is a “Search?”

The question of when government conduct is a Fourth Amendment “search” has received an enormous amount of judicial attention. The doctrine recognizes two tests. First, under United States v. Jones (2012), government conduct is a search if it is a trespass or physical intrusion directed against a person, his house, his papers, or his effects with the intent to obtain information.¹⁹ The second test was announced in Justice John Marshall Harlan II’s concurrence in Katz v. United States (1967).²⁰ Under this test, government conduct is a search if it violates a subjective expectation of privacy and society is prepared to recognize that expectation as objectively reasonable. For the most part, government conduct usually ends up being labeled a search if it is an invasion of a private space such as a home, a car, a package, a letter, or a person’s pockets.²¹ On the other hand, government conduct is ordinarily not labeled a search if it involves surveillance in public.²²

Many of the most difficult cases bearing on what constitutes a Fourth Amendment “search” involve technological surveillance. New technologies can allow the government to obtain information that would previously have been unknowable without a physical trespass into a protected area. These new developments often prompt the question: Is the government’s use of this tool a search on the ground that it obtained private information, or is it not a search on the ground that it was only public surveillance? The cases are complex and have reached varying results. For example, Kyllo v. United States (2001) held that the use of a thermal imaging camera directed at a home to reveal its temperature profile was a search.²³ Carpenter v. United States (2018) ruled that collecting several days of historical cell site location records also was a search.²⁴ On the other hand, California v. Ciraolo (1986) found that aerial surveillance from public airspace is ordinarily not a search.²⁵ And Smith v. Maryland (1979) found that obtaining the numbers dialed from a telephone line is not a search.²⁶

Is a Search or Seizure “Unreasonable?”

Once courts recognize that a search or seizure occurred, the next question is whether the search or seizure was unreasonable and therefore unconstitutional. The standard for reasonableness varies depending on the circumstances, and the doctrine can hinge on very specific distinctions. Under Terry v. Ohio (1968), brief seizures of a person, such as pat-downs, are reasonable as long as they are supported by specific and articulable facts that justify suspicion.²⁷ United States v. Watson (1976) imposes a higher burden to arrest a person: probable cause to believe a crime has been committed and that the arrestee has committed the crime.²⁸ United States v. Robinson (1973) permits the government to search a person who has been arrested incident to that arrest without a warrant.²⁹ However, Riley v. California (2014) held that a warrant is needed to search a person’s cell phone incident to his arrest.³⁰

There are several exceptions to the warrant requirement: (i) searches when exigent circumstances are present; (ii) searches when consent is provided by a party who has authority over the space to be searched; (iii) border searches; (iv) special-needs searches; and others. Horton v. California (1990) recognized the so-called plain view exception.³¹ If the police are lawfully in a position to view evidence that is not described in a warrant but the evidence’s incriminating nature is immediately apparent, they can seize that evidence.

On the whole, the rules for searching homes tend to be the most restrictive among Fourth Amendment doctrines. Entrance to a home is constitutionally reasonable (and therefore legal) only pursuant to a valid warrant or an exception to the warrant requirement.³² The rules for searching and seizing cars tend to give the government significantly broader powers than the rules for homes. Under Whren v. United States (1996), a police officer can order a driver to pull over a car based on any traffic violation, thus seizing the car and its occupants.³³ The officer can then arrest the driver based on only a minor violation, even if the crime of arrest does not provide for any jail time.³⁴ Once the person has been arrested, he can be searched incident to that arrest even if the arrest violates state law.³⁵ Further, the car can be searched without a warrant if there is probable cause to believe that contraband or evidence is located inside it.³⁶

The Exclusionary Rule

After a Fourth Amendment violation has been established, the remaining question is whether there is a remedy for the violation in a court of law. Historically, the primary remedy for Fourth Amendment violations has been the exclusionary rule. The exclusionary rule was established very early in the Fourth Amendment’s development: It was adopted by the U.S. Supreme Court in Weeks v. United States (1914).³⁷ Under the exclusionary rule, evidence obtained as a result of a Fourth Amendment violation may be subject to exclusion from evidence at trial in any subsequent prosecution.³⁸

In general, a defendant can successfully invoke the exclusionary rule only if his own rights were violated and the constitutional violation was the direct cause of the evidence’s being discovered.³⁹ Also, United States v. Leon (1984) and later cases developed the so-called good faith exception to the exclusionary rule.⁴⁰ Under these precedents, the exclusionary rule is a last available resort. Evidence will not be excluded if the officer was acting in good faith; it will be excluded only when the officer who conducted the search acted in a personally culpable manner, as in the case of a knowing or intentional violation.⁴¹

Civil suits can be filed against state officers for Fourth Amendment violations under 42 U.S.C. § 1983, subject to the defense of qualified immunity. Under the doctrine of qualified immunity, an officer is immune from suit unless the violation was clearly established in law at the time and a reasonable officer would have recognized that the act violated the Constitution.⁴²

Open Questions

• What is the future of the exclusionary rule that the Supreme Court adopted in 1914?
• How should the Fourth Amendment adapt to new technology such as computers and the Internet?⁴³
• What is the conceptual basis of the “reasonable expectation of privacy” test, and how is it different (if at all) from the trespass test?

1. 95 Eng. Rep. 807, 817 (KB); 19 Howell’s State Trials 1029, 1063 (KB); 98 Eng. Rep. 489, 498 (KB). ↩︎
2. Thomas Clancy, The Framers’ Intent: John Adams, His Era, and the Fourth Amendment, 86 Ind. L.J. 979, 992–1006 (2011). ↩︎
3. Letter from John Adams to William Tudor, Sr. (Mar. 29, 1817), https://perma.cc/JH4H-GGVW. ↩︎
4. 4 Blackstone 301. ↩︎
5. Pa. Const. of 1776, art. X. ↩︎
6. Mass. Const. of 1780, art. XIV. ↩︎
7. 3 Elliot’s 412. ↩︎
8. Id. at 658. ↩︎
9. 1 Annals of Cong.,1st Cong., 1st Sess. 452 (1789). ↩︎
10. Thomas Y. Davies, Recovering the Original Fourth Amendment, 98 Mich. L. Rev. 547 (1999). ↩︎
11. William J. Cuddihy, The Fourth Amendment: Origins and Original Meaning 602–1791 (2009). ↩︎
12. Akhil Reed Amar, Fourth Amendment First Principles, 107 Harv. L. Rev. 757 (1994). ↩︎
13. Orin S. Kerr, Katz as Originalism, 71 Duke L.J. 1047 (2022). ↩︎
14. United States v. Jacobsen, 466 U.S. 109 (1984). ↩︎
15. United States v. Van Leeuwen, 397 U.S. 249 (1970). ↩︎
16. Brendlin v. California, 551 U.S. 249 (2007). ↩︎
17. Dunaway v. New York, 442 U.S. 200 (1979). ↩︎
18. United States v. Drayton, 536 U.S. 194 (2002). ↩︎
19. 565 U.S. 400 (2012). ↩︎
20. 389 U.S. 347 (1967). ↩︎
21. Silverman v. United States, 365 U.S. 505 (1961); Arizona v. Hicks, 480 U.S. 321 (1987). ↩︎
22. United States v. Knotts, 460 U.S. 276 (1983). ↩︎
23. Kyllo v. United States, 533 U.S. 27 (2001). ↩︎
24. Carpenter v. United States, 585 U.S. 296 (2018). ↩︎
25. California v. Ciraolo, 476 U.S. 207 (1986). ↩︎
26. Smith v. Maryland, 442 U.S. 735 (1979). ↩︎
27. Terry v. Ohio, 391 U.S. 1 (1968). ↩︎
28. United States v. Watson, 423 U.S. 411 (1976). ↩︎
29. United States v. Robinson, 414 U.S. 218 (1973). ↩︎
30. Riley v. California, 573 U.S. 373 (2014). ↩︎
31. Horton v. California, 496 U.S. 128 (1990). ↩︎
32. Payton v. New York, 445 U.S. 573 (1980). ↩︎
33. Whren v. United States, 517 U.S. 806 (1996). ↩︎
34. Atwater v. City of Lago Vista, 532 U.S. 318 (2001). ↩︎
35. Virginia v. Moore, 553 U.S. 164 (2008). ↩︎
36. Carroll v. United States, 267 U.S. 132 (1925). ↩︎
37. 232 U.S. 383 (1914), ↩︎
38. Mapp v. Ohio, 367 U.S. 643 (1961). ↩︎
39. Wong Sun v. United States, 371 U.S. 471 (1963). ↩︎
40. 468 U.S. 897 (1984). ↩︎
41. Davis v. United States, 564 U.S. 229 (2011). ↩︎
42. Anderson v. Creighton, 483 U.S. 635 (1987). ↩︎
43. Orin S. Kerr, The Digital Fourth Amendment: Privacy and Policing in Our Online World (2025). ↩︎