The Fourth Amendment to the United States Constitution is part of the Bill of Rights. It prohibits unreasonable searches and seizures. In addition, it sets requirements for issuing warrants: warrants must be issued by a judge or magistrate, justified by probable cause, supported by oath or affirmation, and must particularly describe the place to be searched and the persons or things to be seized.
In criminal procedure law of the United States, an exigent circumstance allows law enforcement to enter a structure without a search warrant, or if they have a "knock and announce" warrant, allows them to enter without knocking and waiting for the owner's permission to enter. It must be a situation where people are in imminent danger, evidence faces imminent destruction, or a suspect's escape is imminent. Once entry is obtained, the plain view doctrine applies, allowing the seizure of any evidence or contraband discovered in the course of actions consequent upon the exigent circumstances.
United States v. Ross, 456 U.S. 798 (1982), was a search and seizure case argued before the Supreme Court of the United States. The high court was asked to decide if a legal warrantless search of an automobile allows closed containers found in the vehicle to be searched as well. The appeals court had previously ruled that opening and searching the closed portable containers without a warrant was a violation of the Fourth Amendment, even though the warrantless vehicle search was permissible due to existing precedent.
In the United States, the plain view doctrine is an exception to the Fourth Amendment's warrant requirement that allows an officer to seize evidence and contraband that are found in plain view during a lawful observation. The doctrine is also regularly used by Transportation Security Administration (TSA) officers while screening persons and property at U.S. airports.
The motor vehicle exception is a legal rule in the United States that modifies the normal probable cause requirement of the Fourth Amendment to the United States Constitution and, when applicable, allows a police officer to search a motor vehicle without a search warrant.
Arizona v. Hicks, 480 U.S. 321 (1987), held that the Fourth Amendment requires the police to have probable cause to seize items in plain view.
Ker v. California, 374 U.S. 23 (1963), was a case before the United States Supreme Court, which incorporated the Fourth Amendment's protections against illegal search and seizure. The case was decided on June 10, 1963, by a vote of 5–4.
In United States criminal law, the border search exception is a doctrine that allows searches and seizures at international borders and their functional equivalent without a warrant or probable cause. Generally speaking, searches within 100 miles of the border are more permissible without a warrant than those conducted elsewhere in the U.S. The doctrine also allows federal agents to search people at border crossings without a warrant or probable cause. The government is allowed to use scanning devices and to search personal electronics. Invasive bodily searches, however, require reasonable suspicion.
United States v. Ortiz, 422 U.S. 891 (1975), was a United States Supreme Court case in which the Court held that the Fourth Amendment prevented Border Patrol officers from conducting warrantless, suspicionless searches of private vehicles removed from the border or its functional equivalent.
California v. Acevedo, 500 U.S. 565 (1991), was a decision of the United States Supreme Court, which interpreted the Carroll doctrine to provide one rule to govern all automobile searches. The Court stated, "The police may search an automobile and the containers within it where they have probable cause to believe contraband or evidence is contained." The decision also overruled the distinctions in United States v. Chadwick (1977) and Arkansas v. Sanders (1979) which had previously held that, if probable cause existed to search an automobile, the police may perform a warrantless search of the automobile and the containers within it, but if the police only had probable cause to search a container in the automobile, the police first had to obtain a warrant before searching the container.
United States v. Chadwick, 433 U.S. 1 (1977), was a decision by the United States Supreme Court, which held that, absent exigency, the warrantless search of double-locked luggage just placed in the trunk of a parked vehicle is a violation of the Fourth Amendment and not justified under the automobile exception. The Court reasoned that while luggage is movable like an automobile, it does not have the lesser expectation of privacy associated with an automobile.
Wyoming v. Houghton, 526 U.S. 295 (1999), is a United States Supreme Court case which held that absent exigency, the warrantless search of a passenger's container capable of holding the object of a search for which there is probable cause is not a violation of the Fourth Amendment to the United States Constitution because it is justified under the automobile exception as an effect of the car.
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.
Chambers v. Maroney, 399 U.S. 42 (1970), was a United States Supreme Court case in which the Court applied the Carroll doctrine in a case with a significant factual difference—the search took place after the vehicle was moved to the stationhouse. The search was thus delayed and did not take place on the highway as in Carroll. After a gas station robbery, a vehicle fitting the description of the robbers' car was stopped. Inside were people wearing clothing matching the description of that worn by the robbers. They were arrested, and the car was taken to the police station where it was later searched.
Almeida-Sanchez v. United States, 413 U.S. 266 (1973), was a United States Supreme Court case holding that the search of an automobile by the United States Border Patrol without a warrant or probable cause violates the Fourth Amendment. The vehicle was stopped and searched for illegal aliens twenty-five miles (40 km) from the Mexican border. The Court approached the search from four views: automobile search, administrative inspection, heavily regulated industry inspection, and border search. As to the validity of the search under the automobile exception, the Court found no justification for the search under the Carroll doctrine because there was no probable cause. As to the validity of the search under various administrative inspection doctrines, the Court found that the officers lacked an area warrant. As to the validity of the heavily regulated industry inspection, the Court found that the doctrine is not applicable to traveling on a state highway. As to the validity of a border search, the Court found that the site of the stop and the entirety of the road on which the stop occurred was too far from the border to be considered a border search.
Brinegar v. United States, 338 U.S. 160 (1949), was a United States Supreme Court case employing the "reasonableness test" in warrantless searches. The Court held that while the police need not always be factually correct in conducting a warrantless search, such a search must always be reasonable.
Colorado v. Bannister, 449 U.S. 1 (1980), is a U.S. Supreme Court case concerning the automobile exception to constitutional protections against searches and seizures.
Kentucky v. King, 563 U.S. 452 (2011), was a decision by the US Supreme Court, which held that warrantless searches conducted in police-created exigent circumstances do not violate the Fourth Amendment as long as the police did not create the exigency by violating or threatening to violate the Fourth Amendment.
Collins v. Virginia, No. 16-1027, 584 U.S. ___ (2018), was a case before the US Supreme Court involving search and seizure. At issue was whether the Fourth Amendment's motor vehicle exception permits a police officer uninvited and without a warrant to enter private property, approach a house, and search a vehicle parked a few feet from the house that is otherwise visible from off the property. In an 8–1 judgement, the Supreme Court ruled that the automobile exception does not apply to vehicles parked within the home or the curtilage of a private homeowner.
