Fourth Amendment

Katz v. United States, 389 U.S. 347 (1967), is a landmark decision of the U.S. Supreme Court in which the Court redefined what constitutes a "search" or "seizure" with regard to the Fourth Amendment to the U.S. Constitution. The ruling expanded the Fourth Amendment's protections from an individual's "persons, houses, papers, and effects," as specified in the Constitution's text, to include any areas where a person has a "reasonable expectation of privacy."

Weeks v. United States, 232 U.S. 383 (1914) was a United States Supreme Court case in which the Court unanimously held that the warrantless seizure of items from a private residence constitutes a violation of the Fourth Amendment to the U.S. Constitution. It also prevented local officers from securing evidence by means prohibited under the federal exclusionary rule and giving it to their federal colleagues.

Arizona v. Gant, 556 U.S. 332 (2009), was a United States Supreme Court decision holding that the Fourth Amendment to the United States Constitution requires law-enforcement officers to demonstrate an actual and continuing threat to their safety posed by an arrestee, or a need to preserve evidence related to the crime of arrest from tampering by the arrestee, in order to justify a warrantless vehicular search incident to arrest conducted after the vehicle's recent occupants have been arrested and secured.

Terry v. Ohio, 392 U.S. 1 (1968), is a landmark U.S. Supreme Court decision in which the court ruled that it is constitutional for American police to "stop and frisk" a person they reasonably suspect to be armed and involved in a crime. Specifically, the decision held that a police officer does not violate the Fourth Amendment to the U.S. Constitution's prohibition on unreasonable searches and seizures when questioning someone even though the officer lacks probable cause to arrest the person, so long as the police officer has a reasonable suspicion that the person has committed, is…

Illinois v. Lidster, 540 U.S. 419 (2004), was a case in which the Supreme Court of the United States ruled that the Fourth Amendment permits the police to use a roadblock to investigate a traffic incident.

Mapp v. Ohio, 367 U.S. 643 (1961), is a landmark U.S. Supreme Court decision in which the Court ruled that the exclusionary rule, which prevents a prosecutor from using evidence that was obtained by violating the Fourth Amendment to the U.S. Constitution, applies to states as well as the federal government. The Supreme Court accomplished this by use of a principle known as selective incorporation.

Schmerber v. California, 384 U.S. 757 (1966), is a landmark United States Supreme Court case in which the Court clarified the application of the Fourth Amendment's protection against warrantless searches and the Fifth Amendment right against self-incrimination for searches that intrude into the human body. Until Schmerber, the Supreme Court had not yet clarified whether state police officers must procure a search warrant before taking blood samples from criminal suspects.

Silverman v. United States, 365 U.S. 505 (1961), is a United States Supreme Court case in which the Court unanimously held that a federal officer may not, without warrant, physically place themselves into the space of a person's office or home to secretly observe or listen and relate at the man's subsequent criminal trial what was seen or heard.

Berger v. New York, 388 U.S. 41 (1967), was a United States Supreme Court decision invalidating a New York law under the Fourth Amendment, because the statute authorized electronic eavesdropping without required procedural safeguards.

Coolidge v. New Hampshire, 403 U.S. 443 (1971), was a United States Supreme Court case dealing with the Fourth Amendment and the automobile exception. The state sought to justify the search of a car owned by Edward Coolidge, suspected of killing 14-year-old Pamela Mason in January 1964, on three theories: automobile exception, search incident to arrest and plain view.

Smith v. Maryland, 442 U.S. 735 (1979), was a Supreme Court case holding that the installation and use of a pen register by the police to obtain information on a suspect's telephone calls was not a "search" within the meaning of the Fourth Amendment to the United States Constitution, and hence no search warrant was required. In the majority opinion, Justice Harry Blackmun rejected the idea that the installation and use of a pen register constitutes a violation of the suspect's reasonable expectation of privacy since the telephone numbers would be available to and recorded by the phone company…

Johnson v. United States, 333 U.S. 10 (1948), was a significant United States Supreme Court decision addressing search warrants and the Fourth Amendment. In this case, where federal agents had probable cause to search a hotel room but did not obtain a warrant, the Court declared the search was "unreasonable."

Ontario v. Quon, 560 U.S. 746 (2010), is a United States Supreme Court case concerning the extent to which the right to privacy applies to electronic communications in a government workplace. It was an appeal by the city of Ontario, California, from a Ninth Circuit decision holding that it had violated the Fourth Amendment rights of two of its police officers when it disciplined them following an audit of pager text messages that discovered many of those messages were personal in nature, some sexually explicit.

Camara v. Municipal Court, 387 U.S. 523 (1967), is a United States Supreme Court case that overruled a previous case (Frank v. Maryland, 1959) and established the ability of a resident to deny entry to a building inspector without a warrant.

Torres v. Madrid, 592 U.S. 306 (2021), was a United States Supreme Court case based on what constitutes a "seizure" in the context of the Fourth Amendment to the United States Constitution, in the immediate case, in the situation where law enforcement had attempted to use physical force to stop a suspect but failed to do so. The Court ruled in a 5–3 decision that the use of physical force with the intent to restrain a person, even if that fails to restrain the person, is considered a seizure.

Soldal v. Cook County, 506 U.S. 56 (1992), was a United States Supreme Court case in which the Court held that a seizure of property like that which occurs during an eviction, even absent a search or an arrest, implicates the Fourth Amendment. The Court also held that the Amendment protects property as well as privacy interests, in both criminal as well as civil contexts.

Chandler v. Miller, 520 U.S. 305 (1997), was a case before the United States Supreme Court concerning the Constitutionality under the Fourth Amendment of a state statute requiring drug tests of all candidates for certain state offices. The case is notable as being the only one in recent years where the Supreme Court has upheld a challenge to a ballot access restriction from members of a third party, in this case the Libertarian Party of Georgia.

United States v. Jones, 565 U.S. 400 (2012), was a landmark United States Supreme Court case in which the court held that installing a Global Positioning System (GPS) tracking device on a vehicle and using the device to monitor the vehicle's movements constitutes a search under the Fourth Amendment. In 2004, Antoine Jones was suspected by police in the District of Columbia of drug trafficking.

Florida v. Jardines, 569 U.S. 1 (2013), is a Supreme Court of the United States case that ruled that police use of a trained detection dog to sniff for narcotics on the front porch of a private home is a "search" within the meaning of the Fourth Amendment to the United States Constitution, and therefore, without consent, requires both probable cause and a search warrant. In 2006, police in Miami, Florida received an anonymous tip that a home was being used as a marijuana grow house.

Florida v. Royer, 460 U.S. 491 (1983), was a U.S. Supreme Court case dealing with issues involving the Fourth Amendment. Specifically, the case establishes a firm line in cases where police conduct search and seizure without a warrant.

United States v. Mendenhall, 446 U.S. 544 (1980), was a United States Supreme Court case that determined "seizure" occurs when an officer uses displays of authority to detain a person. The United States Court of Appeals for the Sixth Circuit heard the appeal of Ms. Sylvia Mendenhall as pertaining to Ms. Mendenhall's alleged unconstitutional seizure by two DEA agents at Detroit Metropolitan Airport.

Florida v. Bostick, 501 U.S. 429 (1991), was a United States Supreme Court case that overturned a per se rule imposed by the Florida Supreme Court that held consensual searches of passengers on buses were always unreasonable. The Court ruled that the fact that the search takes place on a bus is one factor in determining whether a suspect feels free to decline the search and walk away from the officers.