Fourth Amendment

Fourth Amendment to the United States Constitution
“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 to the United States Constitution, which was ratified with the Bill of Rights in 1791, prohibits the government agents from engaging in unreasonable searches and seizures.  It also prohibits courts from issuing warrants without probable cause.  The Fourth Amendment is applicable to the states and state law enforcement agents through the Fourteenth Amendment.

Fourth Amendment analysis in a nutshell:

  • The Reach of the Fourth Amendment:  
    • The Fourth Amendment applies only to actions by the government, and not to private conduct.  See, e.g., Burdeau v. McDowell, 256 U.S. 456 (1921). Where a private individual acts at the direction of the government agent, however,the search will fall within the umbrella of the Fourth Amendment.  See, e.g., United States v. Newton, 510 F.2d 1149 (7th Cir. 1975) (holding that the search of passenger’s luggage performed by the airline employee at the direction of officers was covered by the Fourth Amendment).
    • The Fourth Amendment does not apply to searches that occurred where the defendant did not have a reasonable expectation of privacy.  See, e.g., Katz v. United States, 389 U.S. 347 (1967) (holding that the defendant had reasonable expectation of privacy in the telephone booth and the government agents’ placing the listening device in the booth without a warrant violated the Fourth Amendment); see also California v. Greenwood, 486 U.S. 35, 39 (1988) (holding that the Fourth Amendment did not apply to a warrantless search of the garbage that was left by the defendant on the street).
  • The Requirements of the Fourth Amendment:
    • The government agents must have “probable cause” for searches and arrests.  However, where an officer is merely questioning a person as part of his investigation, he may “stop and frisk” the person for weapons based on “reasonable suspicion” instead of probable cause.  See Terry v. Ohio, 392 U.S. 1 (1968).
    • A search and/or arrest warrant issued by a court must meet the following requirements:
      • The warrant must be issued by a neutral and detached magistrate;
      • The magistrate must be presented with adequate showing of probable cause supported by oath or affirmation (e.g., affidavits from the police officers); and
      • The warrant must describe with particularity the places to be searched and the items or persons to be seized.

 From U.S. Courts:  What Does the Fourth Amendment Mean?

The Constitution, through the Fourth Amendment, protects people from unreasonable searches and seizures by the government.  The Fourth Amendment, however, is not a guarantee against all searches and seizures, but only those that are deemed unreasonable under the law.

Whether a particular type of search is considered reasonable in the eyes of the law, is determined by balancing two important interests.  On one side of the scale is the intrusion on an individual’s Fourth Amendment rights.  On the other side of the scale are legitimate government interests, such as public safety.

The extent to which an individual is protected by the Fourth Amendment depends, in part, on the location of the search or seizure.  Minnesota v. Carter, 525 U.S. 83 (1998).


  • Searches and seizures inside a home without a warrant are presumptively unreasonable.
    Payton v. New York, 445 U.S. 573 (1980).

However, there are some exceptions. A warrantless search may be lawful:

  • If an officer is given consent to search; Davis v. United States, 328 U.S. 582 (1946)
  • If the search is incident to a lawful arrest; United States v. Robinson, 414 U.S. 218 (1973)
  • If there is probable cause to search and exigent circumstances; Payton v. New York, 445 U.S. 573 (1980)
  • If the items are in plain view; Maryland v. Macon, 472 U.S. 463 (1985).

A Person

  • When an officer observes unusual conduct which leads him reasonably to conclude that criminal activity may be afoot, the officer may briefly stop the suspicious person and make reasonable inquiries aimed at confirming or dispelling the officer’s suspicions.
    Terry v. Ohio, 392 U.S. 1 (1968)
    Minnesota v. Dickerson, 508 U.S. 366 (1993)


  • School officials need not obtain a warrant before searching a student who is under their authority; rather, a search of a student need only be reasonable under all the circumstances.
    New Jersey v. TLO, 469 U.S. 325 (1985)


  • Where there is probable cause to believe that a vehicle contains evidence of a criminal activity, an officer may lawfully search any area of the vehicle in which the evidence might be found.
    Arizona v. Gant, 129 S. Ct. 1710 (2009),
  • An officer may conduct a traffic stop if he has reasonable suspicion that a traffic violation has occurred or that criminal activity is afoot.
    Berekmer v. McCarty, 468 U.S. 420 (1984),
    United States v. Arvizu, 534 U.S. 266 (2002).
  • An officer may conduct a pat-down of the driver and passengers during a lawful traffic stop; the police need not believe that any occupant of the vehicle is involved in a criminal activity.
    Arizona v. Johnson, 555 U.S. 323 (2009).
  • The use of a narcotics detection dog to walk around the exterior of a car subject to a valid traffic stop does not require reasonable, explainable suspicion.
    Illinois v. Cabales, 543 U.S. 405 (2005).
  • Special law enforcement concerns will sometimes justify highway stops without any individualized suspicion.
    Illinois v. Lidster, 540 U.S. 419 (2004).
  • An officer at an international border may conduct routine stops and searches.
    United States v. Montoya de Hernandez, 473 U.S. 531 (1985).
  • A state may use highway sobriety checkpoints for the purpose of combating drunk driving.
    Michigan Dept. of State Police v. Sitz, 496 U.S. 444 (1990).
  • A state may set up highway checkpoints where the stops are brief and seek voluntary cooperation in the investigation of a recent crime that has occurred on that highway.
    Illinois v. Lidster, 540 U.S. 419 (2004).
  • However, a state may not use a highway checkpoint program whose primary purpose is the discovery and interdiction of illegal narcotics.
    City of Indianapolis v. Edmond, 531 U.S. 32 (2000).

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