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 Fourth Amendment prohibits unreasonable searches and seizures. For a judge to issue a search warrant, there must be probable cause and a particularized description of what is to be searched or seized. In Harris v. United States ,1 Footnote
331 U.S. 145 (1947) . the Supreme Court approved as “reasonable” the warrantless search of a four-room apartment pursuant to the arrest of the man found there. A year later, the Court’s majority set aside a conviction based on evidence seized during a warrantless search pursuant to an arrest and adopted the “cardinal rule that, in seizing goods and articles, law enforcement agents must secure and use search warrants wherever reasonably practicable.” 2 Footnote
Trupiano v. United States, 334 U.S. 699, 705 (1948) . See also McDonald v. United States, 335 U.S. 451 (1948) .
This rule was set aside two years later, when the Court held that the test “is not whether it is reasonable to procure a search warrant, but whether the search was reasonable.” 3 Footnote
United States v. Rabinowitz, 339 U.S. 56, 66 (1950) . Whether a search is reasonable, the Court said, “must find resolution in the facts and circumstances of each case.” 4 Footnote
Id. at 63 . The Court, however, returned to its emphasis upon a warrant in Chimel v. California .5 Footnote
395 U.S. 752 (1969) . In Chimel , the Court held that “[t]he [Fourth] Amendment was in large part a reaction to the general warrants and warrantless searches that had so alienated the colonists and had helped speed the movement for independence. In the scheme of the Amendment, therefore, the requirement that ‘no Warrants shall issue, but upon probable cause,’ plays a crucial part.” 6 Footnote
Chimel v. California, 395 U.S. 752, 761 (1969) Therefore, the Court explained, “the police must, whenever practicable, obtain advance judicial approval of searches and seizures through a warrant procedure.” 7 Footnote
Terry v. Ohio, 392 U.S. 1, 20 (1968) . In United States v. U.S. Dist. Ct., 407 U.S. 297, 321 (1972) , Justice Lewis Powell explained that the “very heart” of the Fourth Amendment’s mandate is “that where practical, a governmental search and seizure should represent both the efforts of the officer to gather evidence of wrongful acts and the judgment of the magistrate that the collected evidence is sufficient to justify invasion of a citizen’s private premises or conversation.” Thus, what is “reasonable” in terms of a search and seizure depends on the warrant. Coolidge v. New Hampshire, 403 U.S. 443, 473–84 (1971) . See also Davis v. Mississippi, 394 U.S. 721, 728 (1969) ; Katz v. United States, 389 U.S. 347, 356–58 (1967) ; Warden v. Hayden, 387 U.S. 294, 299 (1967) . Search warrant exceptions would depend on the rationale for the exception, and the scope of such a search would be similarly limited.8 Footnote
Chimel v. California, 395 U.S. 752, 762–64 (1969) (limiting scope of search incident to arrest). See also United States v. United States District Court, 407 U.S. 297 (1972) (rejecting argument that it was “reasonable” to allow President through Attorney General to authorize warrantless electronic surveillance of persons thought to be endangering the national security); Katz v. United States, 389 U.S. 347 (1967) (although officers acted with great self-restraint and reasonably in engaging in electronic seizures of conversations from a telephone booth, a magistrate’s antecedent judgment was required); Preston v. United States, 376 U.S. 364 (1964) (warrantless search of seized automobile not justified because not within rationale of exceptions to warrant clause). There were exceptions, e.g., Cooper v. California, 386 U.S. 58 (1967) (warrantless search of impounded car was reasonable); United States v. Harris, 390 U.S. 234 (1968) (warrantless inventory search of automobile).
During the 1970s, the Court was closely divided on which standard to apply.9 Footnote
See, e.g., Almighty-Sanchez v. United States, 413 U.S. 266 (1973) , Justices Potter Stewart, William O. Douglas, William Brennan, and Thurgood Marshall adhered to the warrant-based rule, while Justices Byron White, Harry Blackmun, and William Rehnquist, and Chief Justice Warren Burger placed greater emphasis upon whether the search was reasonable. Id. at 285 . Justice Lewis Powell generally agreed with the former group of Justices, id. at 275 (concurring). For a while, the Court adopted the view that warrantless searches were per se unreasonable, with a few carefully prescribed exceptions.10 Footnote
E.g., G.M. Leasing Corp. v. United States, 429 U.S. 338, 352–53 (1977) (unanimous); Marshall v. Barrow’s, Inc., 436 U.S. 307, 312 (1978) ; Michigan v. Tyler, 436 U.S. 499, 506 (1978) ; Mincey v. Arizona, 437 U.S. 385, 390 (1978) (unanimous); Arkansas v. Sanders, 442 U.S. 753 (1979) ; United States v. Ross, 456 U.S. 798, 824–25 (1982) . Gradually, however, guided by the variable-expectation-of-privacy approach to the Fourth Amendment’s coverage, the Court broadened its view of permissible exceptions and the scope of those exceptions.11 Footnote
E.g., Chambers v. Maroney, 399 U.S. 42 (1970) (warrantless search of automobile taken to police station); Texas v. White, 423 U.S. 67 (1975) (same); New York v. Belton, 453 U.S. 454 (1981) (search of vehicle incident to arrest); United States v. Ross, 456 U.S. 798 (1982) (automobile search at scene); Brigham City, Utah v. Stuart, 547 U.S. 398 (2006) (warrantless entry into a home when police have an objectively reasonable basis for believing that an occupant is seriously injured or imminently threatened with such injury); Michigan v. Fisher , 558 U.S. 45 (2009) (applying Brigham City ). On the other hand, the warrant-based standard did preclude a number of warrantless searches. E.g., Almighty-Sanchez v. United States, 413 U.S. 266 (1973) (warrantless stop and search of auto by roving patrol near border); Marshall v. Barrow’s, Inc., 436 U.S. 307 (1978) (warrantless administrative inspection of business premises); Mincey v. Arizona, 437 U.S. 385 (1978) (warrantless search of home that was “homicide scene” ); Arizona v. Gant, 556 U.S. 332 (2009) (search of vehicle incident to arrest where arrestee had no access to vehicle). In 1991, the Court held that “[t]he touchstone of the Fourth Amendment is reasonableness,” and that the Amendment “merely proscribes [state-initiated searches and seizures] which are unreasonable.” 12 Footnote
Florida v. Jimeno, 500 U.S. 248, 250 (1991) . By 1992, the “reasonableness” approach prevailed over the “warrants-with-narrow-exceptions” standard.13 Footnote
Of the Justices on the Court in 1992, only Justice John Paul Stevens frequently sided with the warrants-with-narrow-exceptions approach. See, e.g., Illinois v. Rodriguez, 497 U.S. 177, 189 (1990) (Marshall, J., dissenting joined by Stevens, J.); New Jersey v. T.L.O., 469 U.S. 325, 370 (1985) (Stevens, J., dissenting); California v. Acevedo, 500 U.S. 565, 585 (1991) (Stevens, J., dissenting). The Court held that “reasonableness, in turn, is measured in objective terms by examining the totality of the circumstances,” and the Court had “consistently eschewed bright-lines rules.” 14 Footnote
Ohio v. Robinette, 519 U.S. 33, 39 (1996) . Since the 1990s, the Court has recognized more exceptions to the warrant requirement, tending to confine the warrant requirement to cases that are exclusively “criminal” in nature. Furthermore, even within that core area of “criminal” cases, the Court broadened some exceptions. Nevertheless, throughout the years, the Court has grappled with what constitutes a search15 Footnote
See e.g., Katz v. United States, 389 U.S. 347, 351–52 (1967) ( “What a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection. But what he seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected.” ). or a seizure,16 Footnote
See e.g., Torres v. Madrid , No. 19-292, slip op. at 3 (U.S. March 25, 2021) ( “The ‘seizure’ of a ‘person’ plainly refers to an arrest.” ); see also Olmstead v. United States, 277 U.S. 438 (1928) ; but see Warden v. Hayden, 387 U.S. 294, 304 (1967) (explaining the Court’s “shift in emphasis from property to privacy ha[d] come about through a subtle interplay of substantive and procedural reform” ). what does it mean to establish probable cause,17 Footnote
See e.g., Henry v. United States, 361 U.S. 98, 102 (1959) ( “Probable cause exists if the facts and circumstances known to the officer warrant a prudent man in believing that the offense has been committed.)” . when are warrants necessary,18 Footnote
See e.g., Terry v. Ohio, 392 U.S. 1, 20 (1968) ( “[T]he police must, whenever practicable, obtain advance judicial approval of searches and seizures through the warrant procedure.” ). and what are the various exceptions to the warrant requirement.
Administrative searches justified by “special needs beyond the normal need for law enforcement” are the most important exception to the warrant requirement.19 Footnote
New Jersey v. T.L.O., 469 U.S. 325, 351 (1985) (Blackmun, J., concurring). Under this general rubric the Court has upheld warrantless searches by administrative authorities in public schools,20 Footnote
Id. at 341 (holding that “the accommodation of the privacy interests of schoolchildren with the substantial need of teachers and administrators for freedom to maintain order in the schools does not require strict adherence to the requirement that searches be based on probable cause to believe that the subject of the search has violated or is violating the law” ). government offices,21 Footnote
See O’Connor v. Ortega, 480 U.S. 709, 724–25 (1987) (holding that “a probable cause requirement” for searches conducted to work-related investigations “would impose intolerable burdens on public employers” ). and prisons,22 Footnote
See Hudson v. Palmer, 468 U.S. 517, 526 (1984) (explaining that a prisoner has no expectation of privacy and, accordingly, “the Fourth Amendment proscription against unreasonable searches does not apply within the confines of the prison cell” ). and drug testing of public and transportation employees.23 Footnote
See Skinner v. Ry. Lab. Exec. Ass’n, 489 U.S. 602, 614 (1989) ; Nat’l Treasury Emps. Union v. Von Raab, 489 U.S. 656, 672 (1989) In all of these instances, the warrant and probable cause requirements are dispensed with in favor of a reasonableness standard that balances the government’s regulatory interest against the individual’s privacy interest. The breadth of the administrative search exception is shown by the fact overlapping law enforcement objectives and administrative “special needs” do not require a warrant; instead, the Court has upheld warrantless inspection of automobile junkyards and dismantling operations in spite of the strong law enforcement component of the regulation.24 Footnote
New York v. Burger, 482 U.S. 691 (1987) .
Although search warrants are generally required in law enforcement contexts, the Court has relaxed this requirement. For example, the Court expanded the scope of valid “incident to arrest” searches from areas within the immediate reach of the arrested suspect to a “protective sweep” of the entire home, if arresting officers have a “reasonable” belief that the home harbors an individual who may pose a danger.25 Footnote
Maryland v. Buie, 494 U.S. 325 (1990) . The Court has also recognized that exigent circumstances may justify officers performing a blood test on a motorist without a warrant to determine his or her blood alcohol concentration (BAC).26 Footnote
See Missouri v. McNeely , 569 U.S. 141, 156 (2013) (rejecting a per se exception to the warrant requirement for BAC blood testing in suspected “drunk-driving” cases and requiring that exigent circumstances be evaluated under a “totality of the circumstances” test). Cf. Mitchell v. Wisconsin , No. 18-6210, (U.S. June 27, 2019) (plurality opinion) (declining to “revisit” the rule established in McNeely but concluding that in circumstances involving unconscious drivers, where a breath test for BAC cannot be performed, exigent circumstances generally exist to take a warrantless blood test). In another case, the Court shifted its focus from whether exigent circumstances justified an officer’s failure to obtain a warrant, to whether an officer had a “reasonable” belief that the circumstances constituted an exception to the warrant requirement.27 Footnote
Illinois v. Rodriguez, 497 U.S. 177 (1990) . The Court has also held exigent circumstances merited an exception even if police conduct had caused the exigency, so long as the police conduct was “reasonable” in that it neither threatened to violate nor violated the Fourth Amendment.28 Footnote
Kentucky v. King , 563 U.S. 452 (2011) (police justified in entering apartment after smelling burning marijuana in a hallway, knocking on apartment door, and hearing noises consistent with evidence being destroyed).
The Court has addressed the Fourth Amendment’s scope with respect to whom the Fourth Amendment protects; that is, who constitutes “the people,” reasoning that it “refers to a class of persons who are part of a national community or who have otherwise developed sufficient connection with [the United States] to be considered part of that community.” 29 Footnote
United States v. Vertigo-Urquidez, 494 U.S. 259, 265 (1990) . The Fourth Amendment therefore does not apply to the search and seizure by United States agents of property that is owned by a nonresident alien and located in a foreign country.30 Footnote
Id. at 266 ( “[T]he purpose of the Fourth Amendment was to protect the people of the United States against arbitrary action by their own Government; it was never suggested that the provision was intended to restrain the actions of the Federal Government against aliens outside of the United States territory.” ) The community of protected people includes U.S. citizens who go abroad, and aliens who have voluntarily entered U.S. territory and developed substantial connections with this country.31 Footnote
Id. at 271–72 . There is no resulting broad principle, however, that the Fourth Amendment constrains federal officials wherever and against whomever they act.
Footnotes 1 331 U.S. 145 (1947) . 
2 Trupiano v. United States, 334 U.S. 699, 705 (1948) . See also McDonald v. United States, 335 U.S. 451 (1948) . 3 United States v. Rabinowitz, 339 U.S. 56, 66 (1950) . 4 Id. at 63 . 5 395 U.S. 752 (1969) . 6 Chimel v. California, 395 U.S. 752, 761 (1969) 7 Terry v. Ohio, 392 U.S. 1, 20 (1968) . In United States v. U.S. Dist. Ct., 407 U.S. 297, 321 (1972) , Justice Lewis Powell explained that the “very heart” of the Fourth Amendment’s mandate is “that where practical, a governmental search and seizure should represent both the efforts of the officer to gather evidence of wrongful acts and the judgment of the magistrate that the collected evidence is sufficient to justify invasion of a citizen’s private premises or conversation.” Thus, what is “reasonable” in terms of a search and seizure depends on the warrant. Coolidge v. New Hampshire, 403 U.S. 443, 473–84 (1971) . See also Davis v. Mississippi, 394 U.S. 721, 728 (1969) ; Katz v. United States, 389 U.S. 347, 356–58 (1967) ; Warden v. Hayden, 387 U.S. 294, 299 (1967) . 8 Chimel v. California, 395 U.S. 752, 762–64 (1969) (limiting scope of search incident to arrest). See also United States v. United States District Court, 407 U.S. 297 (1972) (rejecting argument that it was “reasonable” to allow President through Attorney General to authorize warrantless electronic surveillance of persons thought to be endangering the national security); Katz v. United States, 389 U.S. 347 (1967) (although officers acted with great self-restraint and reasonably in engaging in electronic seizures of conversations from a telephone booth, a magistrate’s antecedent judgment was required); Preston v. United States, 376 U.S. 364 (1964) (warrantless search of seized automobile not justified because not within rationale of exceptions to warrant clause). There were exceptions, e.g., Cooper v. California, 386 U.S. 58 (1967) (warrantless search of impounded car was reasonable); United States v. Harris, 390 U.S. 234 (1968) (warrantless inventory search of automobile). 9 See, e.g., Almighty-Sanchez v. United States, 413 U.S. 266 (1973) , Justices Potter Stewart, William O. Douglas, William Brennan, and Thurgood Marshall adhered to the warrant-based rule, while Justices Byron White, Harry Blackmun, and William Rehnquist, and Chief Justice Warren Burger placed greater emphasis upon whether the search was reasonable. Id. at 285 . Justice Lewis Powell generally agreed with the former group of Justices, id. at 275 (concurring). 10 E.g., G.M. Leasing Corp. v. United States, 429 U.S. 338, 352–53 (1977) (unanimous); Marshall v. Barrow’s, Inc., 436 U.S. 307, 312 (1978) ; Michigan v. Tyler, 436 U.S. 499, 506 (1978) ; Mincey v. Arizona, 437 U.S. 385, 390 (1978) (unanimous); Arkansas v. Sanders, 442 U.S. 753 (1979) ; United States v. Ross, 456 U.S. 798, 824–25 (1982) . 11 E.g., Chambers v. Maroney, 399 U.S. 42 (1970) (warrantless search of automobile taken to police station); Texas v. White, 423 U.S. 67 (1975) (same); New York v. Belton, 453 U.S. 454 (1981) (search of vehicle incident to arrest); United States v. Ross, 456 U.S. 798 (1982) (automobile search at scene); Brigham City, Utah v. Stuart, 547 U.S. 398 (2006) (warrantless entry into a home when police have an objectively reasonable basis for believing that an occupant is seriously injured or imminently threatened with such injury); Michigan v. Fisher , 558 U.S. 45 (2009) (applying Brigham City ). On the other hand, the warrant-based standard did preclude a number of warrantless searches. E.g., Almighty-Sanchez v. United States, 413 U.S. 266 (1973) (warrantless stop and search of auto by roving patrol near border); Marshall v. Barrow’s, Inc., 436 U.S. 307 (1978) (warrantless administrative inspection of business premises); Mincey v. Arizona, 437 U.S. 385 (1978) (warrantless search of home that was “homicide scene” ); Arizona v. Gant, 556 U.S. 332 (2009) (search of vehicle incident to arrest where arrestee had no access to vehicle). 12 Florida v. Jimeno, 500 U.S. 248, 250 (1991) . 13 Of the Justices on the Court in 1992, only Justice John Paul Stevens frequently sided with the warrants-with-narrow-exceptions approach. See, e.g., Illinois v. Rodriguez, 497 U.S. 177, 189 (1990) (Marshall, J., dissenting joined by Stevens, J.); New Jersey v. T.L.O., 469 U.S. 325, 370 (1985) (Stevens, J., dissenting); California v. Acevedo, 500 U.S. 565, 585 (1991) (Stevens, J., dissenting). 14 Ohio v. Robinette, 519 U.S. 33, 39 (1996) . 15 See e.g., Katz v. United States, 389 U.S. 347, 351–52 (1967) ( “What a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection. But what he seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected.” ). 16 See e.g., Torres v. Madrid , No. 19-292, slip op. at 3 (U.S. March 25, 2021) ( “The ‘seizure’ of a ‘person’ plainly refers to an arrest.” ); see also Olmstead v. United States, 277 U.S. 438 (1928) ; but see Warden v. Hayden, 387 U.S. 294, 304 (1967) (explaining the Court’s “shift in emphasis from property to privacy ha[d] come about through a subtle interplay of substantive and procedural reform” ). 17 See e.g., Henry v. United States, 361 U.S. 98, 102 (1959) ( “Probable cause exists if the facts and circumstances known to the officer warrant a prudent man in believing that the offense has been committed.)” . 18 See e.g., Terry v. Ohio, 392 U.S. 1, 20 (1968) ( “[T]he police must, whenever practicable, obtain advance judicial approval of searches and seizures through the warrant procedure.” ). 19 New Jersey v. T.L.O., 469 U.S. 325, 351 (1985) (Blackmun, J., concurring). 20 Id. at 341 (holding that “the accommodation of the privacy interests of schoolchildren with the substantial need of teachers and administrators for freedom to maintain order in the schools does not require strict adherence to the requirement that searches be based on probable cause to believe that the subject of the search has violated or is violating the law” ). 21 See O’Connor v. Ortega, 480 U.S. 709, 724–25 (1987) (holding that “a probable cause requirement” for searches conducted to work-related investigations “would impose intolerable burdens on public employers” ). 22 See Hudson v. Palmer, 468 U.S. 517, 526 (1984) (explaining that a prisoner has no expectation of privacy and, accordingly, “the Fourth Amendment proscription against unreasonable searches does not apply within the confines of the prison cell” ). 23 See Skinner v. Ry. Lab. Exec. Ass’n, 489 U.S. 602, 614 (1989) ; Nat’l Treasury Emps. Union v. Von Raab, 489 U.S. 656, 672 (1989) 24 New York v. Burger, 482 U.S. 691 (1987) . 25 Maryland v. Buie, 494 U.S. 325 (1990) . 26 See Missouri v. McNeely , 569 U.S. 141, 156 (2013) (rejecting a per se exception to the warrant requirement for BAC blood testing in suspected “drunk-driving” cases and requiring that exigent circumstances be evaluated under a “totality of the circumstances” test). Cf. Mitchell v. Wisconsin , No. 18-6210, (U.S. June 27, 2019) (plurality opinion) (declining to “revisit” the rule established in McNeely but concluding that in circumstances involving unconscious drivers, where a breath test for BAC cannot be performed, exigent circumstances generally exist to take a warrantless blood test). 27 Illinois v. Rodriguez, 497 U.S. 177 (1990) . 28 Kentucky v. King , 563 U.S. 452 (2011) (police justified in entering apartment after smelling burning marijuana in a hallway, knocking on apartment door, and hearing noises consistent with evidence being destroyed). 29 United States v. Vertigo-Urquidez, 494 U.S. 259, 265 (1990) . 30 Id. at 266 ( “[T]he purpose of the Fourth Amendment was to protect the people of the United States against arbitrary action by their own Government; it was never suggested that the provision was intended to restrain the actions of the Federal Government against aliens outside of the United States territory.” ) 31 Id. at 271–72 .
