United States Constitution, Amendment IV

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.

Editorial note. The Fourth Amendment responds directly to Crown practices of general warrants and writs of assistance in the American colonies. James Otis's 1761 argument against writs of assistance in the Massachusetts Superior Court, and the English cases Entick v. Carrington, 19 How. St. Tr. 1029 (K.B. 1765), and Wilkes v. Wood, 98 Eng. Rep. 489 (K.B. 1763), supplied the doctrinal grammar the Framers translated into constitutional text.

Editorial note. The Amendment protects individual privacy and security against arbitrary governmental intrusion by imposing an ex ante judicial check (the warrant requirement) and an ex post standard of reasonableness on all executive searches and seizures.

Editorial note. The Amendment consists of two clauses. The Reasonableness Clause forbids unreasonable searches and seizures. The Warrant Clause specifies the conditions under which warrants may issue: probable cause, oath or affirmation, and particularity of place and things.

Editorial note. The Amendment reaches only governmental action; it does not regulate private searches. Its protections attach where the individual has a reasonable expectation of privacy (Katz v. United States, 389 U.S. 347 (1967)) or where the government physically intrudes upon a constitutionally protected area (United States v. Jones, 565 U.S. 400 (2012)).

Editorial note. Foundational cases include Weeks v. United States, 232 U.S. 383 (1914) (federal exclusionary rule); Mapp v. Ohio, 367 U.S. 643 (1961) (exclusionary rule applied to States); Terry v. Ohio, 392 U.S. 1 (1968) (stop-and-frisk on reasonable suspicion); Katz v. United States, 389 U.S. 347 (1967) (reasonable-expectation-of-privacy test); Kyllo v. United States, 533 U.S. 27 (2001) (thermal imaging of home); Riley v. California, 573 U.S. 373 (2014) (warrant required for cell-phone search incident to arrest); Carpenter v. United States, 585 U.S. 296 (2018) (historical cell-site location information).

Editorial note. Fourth Amendment doctrine now confronts digital searches, aerial surveillance, third-party data holdings, and administrative inspections. The reasonableness inquiry, the warrant preference, and the exceptions to it (exigency, consent, plain view, search incident to arrest, automobile, inventory, special needs) remain the analytic framework.

Editorial note. Read together with U.S. Const. amend. V (self-incrimination; due process) and U.S. Const. amend. XIV, § 1 (incorporation against the States). Statutory analogs include the Federal Wiretap Act, 18 U.S.C. §§ 2510–2523, and the Stored Communications Act, 18 U.S.C. §§ 2701–2713.

Editorial note. The Fourth Amendment governs every arrest, investigatory stop, search of premises or effects, and seizure of physical or digital evidence conducted by federal, state, or local government actors.