Search, Seizure, and Warrants

Two clauses, and the order of the questions

The Fourth Amendment is one sentence with two working parts. The first secures the right of the people to be secure in their persons, houses, papers, and effects against unreasonable searches and seizures. The second says 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. Notice what the text does not say: it never commands police to get a warrant. It forbids unreasonable searching, and sets terms for warrants.

Courts filled that gap with a presumption. Katz v. United States (1967) called searches conducted without prior approval by a judge or magistrate per se unreasonable, subject only to a few specifically established and well-delineated exceptions. Kentucky v. King (2011) restated it: warrantless searches of a home are presumptively unreasonable, but that presumption can be overcome when the exigencies of a situation make a warrantless search objectively reasonable. The practical law therefore lives in the exceptions; whoever memorizes the presumption without them has learned the smaller half.

Work any problem in this order. First, did government action amount to a search or a seizure at all? If not, the Amendment has nothing to say. Second, was there a warrant, and was it valid? Third, if not, does an exception apply? Only then comes the remedial question: what happens to the evidence, and who may raise it.

What counts as a search

Originally a search meant a trespass on a protected place; Katz ended that monopoly. FBI agents taped a listening device to the outside of a public telephone booth, entering nothing. Justice Stewart's opinion answered that the Fourth Amendment protects people, not places, so its reach cannot turn on the presence or absence of a physical intrusion. The same passage adds a limit students skip: what a person knowingly exposes to the public, even in his own home or office, is not protected.

The test everyone cites is not in the majority opinion. Justice Harlan, concurring, described a twofold requirement - that a person have exhibited an actual, subjective expectation of privacy, and that the expectation be one society is prepared to recognize as reasonable. Later cases adopted it, and that is what courts mean by the Katz test.

The trespass idea never died. In United States v. Jones (2012) agents attached a GPS tracker to a car and monitored it for 28 days. Justice Scalia's opinion found a search without reaching privacy at all: the government had physically occupied private property for the purpose of obtaining information. Katz, the Court said, has been added to, but not substituted for, the common-law trespassory test. Florida v. Jardines (2013) ran that route at a house, holding that bringing a drug-detection dog onto a front porch was a search, because the porch is curtilage, which counts as part of the home itself.

Sensing technology has its own line. Kyllo v. United States (2001) held that aiming a thermal imager at a house was a search, because the device was not in general public use and exposed details of a home otherwise unknowable without physical intrusion. Carpenter v. United States (2018) reached records rather than rooms: acquiring 127 days of a suspect's historical cell-site location information was a search, and a Stored Communications Act order resting on reasonable grounds fell well short of the probable cause a warrant requires.

What counts as a seizure of a person

Property is seized when the government meaningfully interferes with a possessory interest. A person is seized on a different test, and the line matters because officers may approach and question anyone without any justification. United States v. Mendenhall (1980) supplied the phrase: a person has been seized only if, in view of all the circumstances, a reasonable person would have believed he was not free to leave. Justice Stewart's opinion drew only one other vote on that point, but later majorities adopted it. It also listed the tells: several officers present, a displayed weapon, physical touching, or a tone indicating that compliance is expected - illustrations, not requirements.

Florida v. Bostick (1991) fixed a defect in that phrasing, in a case where officers questioned passengers on a stopped bus nobody wanted to leave. Justice O'Connor's opinion rejected the Florida court's per se rule that every such encounter is a seizure, and restated the question: whether a reasonable person would feel free to decline the officers' requests or otherwise terminate the encounter.

California v. Hodari D. (1991) added the timing rule. A seizure requires either the application of physical force, however slight, or - absent force - submission to a show of authority. Hodari kept running after an officer gave chase, so he was not seized until he was tackled, and the drugs he threw away while running were not the fruit of any seizure. Torres v. Madrid (2021) completed the force half: applying physical force to the body of a person with intent to restrain is a seizure even if the person does not submit and is not subdued.

What a valid warrant requires

A warrant is advance permission from someone who is not investigating the case. Probable cause is the quantum of justification, and Illinois v. Gates (1983) fixed how it is measured. Justice Rehnquist's opinion discarded the rigid two-pronged test that had governed informant tips in favor of a totality-of-the-circumstances approach: the magistrate makes a practical, common-sense decision whether there is a fair probability that contraband or evidence of a crime will be found in a particular place, and a reviewing court asks only whether he had a substantial basis for that conclusion. Oath or affirmation is the accountability element - someone swears to the facts. Particularity is the anti-general-warrant element: the document must name the place and the things, so the officer executing it is not deciding on the doorstep how far to go. And the issuer must be a neutral judicial officer, not the investigating agency.

Federal Rule of Criminal Procedure 41 shows what those abstractions look like as paperwork. A judge issues the warrant only on probable cause. It must identify what is to be searched and anything to be seized, command execution within a specified time no longer than fourteen days, and command daytime execution unless the judge finds good cause otherwise. The officer then prepares a verified inventory, leaves a copy and a receipt, and returns the warrant to the judge.

Warrants also mark a spatial boundary. Payton v. New York (1980) held that police may not enter a home without a warrant or consent to make a routine felony arrest: the Amendment draws a firm line at the entrance to the house that, absent exigent circumstances, may not be crossed.

The recognized exceptions

Consent. If a person voluntarily agrees, no warrant and no cause are needed. Schneckloth v. Bustamonte (1973) held that voluntariness is judged on the totality of the circumstances, and that although knowledge of a right to refuse is a factor, the prosecution need not prove it existed. Georgia v. Randolph (2006) added that a physically present occupant's express refusal defeats a co-occupant's consent as to the objector.

Exigent circumstances. When waiting would defeat the purpose - imminent destruction of evidence, an emergency, an escaping suspect - officers may act without a warrant. Kentucky v. King (2011) added the limit that matters: the exception is available so long as police did not create the exigency by engaging or threatening to engage in conduct that violates the Fourth Amendment. Two later cases refused to make exigency categorical. Missouri v. McNeely (2013) held that the natural dissipation of alcohol in the bloodstream is not by itself an exigency in every drunk-driving case, and Lange v. California (2021) held that pursuit of a fleeing misdemeanor suspect does not always - that is, categorically - justify a warrantless home entry.

Search incident to lawful arrest. Chimel v. California (1969) confined it to the arrestee's person and the area within his immediate control - the space from which he might grab a weapon or destructible evidence - and required a warrant for other rooms. Arizona v. Gant (2009) applied that logic to cars: officers may search the passenger compartment incident to a recent occupant's arrest only if the arrestee might access the vehicle at the time of the search, or it is reasonable to believe the vehicle contains evidence of the offense of arrest. Gant was handcuffed in a patrol car, so neither branch fit him. Riley v. California (2014) drew the line for phones: digital data stored on a phone cannot itself be used as a weapon, so the Chimel rationales do not reach it, and the Court's instruction was three words - get a warrant - though exigency remains available.

The automobile exception. Carroll v. United States (1925) held that the right to search a movable vehicle on probable cause that it carries contraband does not depend on the right to arrest anyone. California v. Acevedo (1991) carried that into containers: officers with probable cause as to a container inside a car may open it without a warrant.

Plain view. Horton v. California (1990) held that inadvertent discovery is not required, then restated what is: the officer must have reached the vantage point lawfully, the object's incriminating character must be immediately apparent, and the officer must have a lawful right of access to the object.

Stop and frisk. Terry v. Ohio (1968) recognized a brief, lesser intrusion on less than probable cause. Chief Justice Warren's opinion conceded both halves the state had denied - restraining someone's freedom to walk away is a seizure, and running hands over the outside of clothing is a search - then held both can be justified when the officer points to specific and articulable facts, taken with rational inferences from them, rather than an inchoate and unparticularized suspicion or hunch. The frisk is limited to weapons. Later cases supplied the label reasonable suspicion; in Terry itself that phrase appears only in Justice Douglas's dissent.

Searches that are not looking for a crime

A separate family of searches is measured against reasonableness without individualized suspicion, because the purpose is not criminal investigation. Camara v. Municipal Court (1967) held that a municipal inspector needs a warrant to enter a dwelling over the occupant's objection, but that probable cause for an area-inspection warrant may rest on reasonable legislative or administrative standards rather than suspicion about the particular building. South Dakota v. Opperman (1976) upheld the routine inventory of a lawfully impounded car, conducted under standard police procedures, as reasonable without a warrant. Skinner v. Railway Labor Executives' Association (1989) upheld regulations requiring blood and urine tests of railroad employees after major accidents, calling the government's interest a special need beyond normal law enforcement that can justify departing from the usual warrant and probable-cause requirements. What holds the family together is that standardized criteria, not an officer's judgment, supply the check.

Whose rights, what remedy, and the floor states may raise

Fourth Amendment rights are personal. Rakas v. Illinois (1978) held that passengers who claimed no interest in the car or in the rifle and shells taken from it could not challenge the search, folding the older label of standing into the substantive question: whether the person claiming the Amendment's protection had a legitimate expectation of privacy in the invaded place. A defendant hurt by evidence gathered through a violation of someone else's rights usually has no suppression claim.

Where the right is the defendant's own, the principal consequence is exclusion: evidence obtained in violation of the Fourth Amendment is generally kept out of the prosecution's case, and Mapp v. Ohio (1961) made that binding on the states. The mechanism is procedural - Rule 41(h) routes a federal defendant to Rule 12 to move to suppress - but the stakes are the case. Exclusion is not automatic: United States v. Leon (1984) held that evidence stays in when officers rely in objectively reasonable good faith on a warrant issued by a detached and neutral magistrate that later proves invalid, because suppressing it would deter nothing - though the magistrate may not serve as a rubber stamp. That rule's history and other exceptions belong to this curriculum's constitutional-protections lesson.

One caution follows every Fourth Amendment analysis: all of the above is a federal floor. As the Court put it in Oregon v. Hass (1975), a state is free as a matter of its own law to impose greater restrictions on police activity than federal constitutional standards require. Several state supreme courts read their own search-and-seizure provisions more protectively, so the same conduct can be lawful federally and unlawful under a state constitution. This lesson is educational material about United States law. It is not legal advice, and it does not state the law of any particular state.