The Fourth Amendment to the United States Constitution is part of the Bill of Rights. It prohibits unreasonable searches and seizures and 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.
Search and seizure is a procedure used in many civil law and common law legal systems by which police or other authorities and their agents, who, suspecting that a crime has been committed, commence a search of a person's property and confiscate any relevant evidence found in connection to the crime.
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.
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.
Chimel v. California, 395 U.S. 752 (1969), was a 1969 United States Supreme Court case in which the court held that police officers arresting a person at his home could not search the entire home without a search warrant, but that police may search the area within immediate reach of the person without a warrant. The rule on searches incident to a lawful arrest within the home is now known as the Chimel rule.
South Dakota v. Opperman, 428 U.S. 364 (1976), elaborated on the community caretaking doctrine. Under the Fourth Amendment, "unreasonable" searches and seizures are forbidden. In addition to their law-enforcement duties, the police must engage in what the court has termed a community caretaking role, including such duties as removing obstructions from roadways to ensure the free flow of traffic. When the police act in this role, they may inventory cars they have seized without "unreasonably" searching those cars.
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.
Payton v. New York, 445 U.S. 573 (1980), was a United States Supreme Court case concerning warrantless entry into a private home in order to make a felony arrest. The Court struck down a New York statute providing for such warrantless entries because the Fourth Amendment draws a firm line at the entrance to the house. Absent exigent circumstances, that threshold may not be reasonably crossed without a warrant. The court, however, did specify that an arrest warrant would have sufficed for entry into the suspect's residence if there had been reason to believe that the suspect was within the home.
Welsh v. Wisconsin, 466 U.S. 740 (1984), was a 1983 case before the US Supreme Court determining that a warrantless home arrest without exigent circumstances violates the Fourth Amendment protection against unlawful search and seizure.
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.
California v. Carney, 471 U.S. 386 (1985), was a United States Supreme Court case which held that a motor home was subject to the automobile exception to the search warrant requirement of the Fourth Amendment to the United States Constitution because the motor home was readily movable.
Horton v. California, 496 U.S. 128 (1990), was a United States Supreme Court case in which the Court held that the Fourth Amendment does not prohibit the warrantless seizure of evidence which is in plain view. The discovery of the evidence does not have to be inadvertent, although that is a characteristic of most legitimate plain-view seizures. The opinion clarified the plain view doctrine of the Court's Fourth Amendment analysis.
Cupp v. Murphy, 412 U.S. 291 (1973), was a United States Supreme Court case in which the Court upheld a murder conviction notwithstanding a challenge that the evidence upon which guilt was based was obtained in violation of the Fourth and Fourteenth Amendments of the United States Constitution. The court held that in view of the station-house detention upon probable cause, the very limited intrusion of scraping the defendant's fingernails for blood and other material, undertaken to preserve highly evanescent evidence, did not violate the Fourth and Fourteenth Amendments.
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.
United States v. Watson, 423 U.S. 411 (1976), was a case decided by the Supreme Court of the United States that decided that a warrantless arrest in public and consenting to a vehicle search did not violate the Fourth Amendment.
Birchfield v. North Dakota, 579 U.S. 438 (2016) is a case in which the Supreme Court of the United States held that the search incident to arrest doctrine permits law enforcement to conduct warrantless breath tests but not blood tests on suspected drunk drivers.
Caniglia v. Strom, 593 U.S. ___ (2021), was a United States Supreme Court case related to the Fourth Amendment to the United States Constitution's "community caretaking" exception.
Stone v. Powell, 428 U.S. 465 (1976), was decision of the Supreme Court of the United States that limited which claims of Fourth Amendment violations could be made by state prisoners in habeas corpus petitions in federal courts. Specifically, a claim that the exclusionary rule had been broken would be barred if state courts had already given it a full and fair hearing. The decision combined two cases that were argued before the Supreme Court on the same day with similar issues, one filed by Lloyd Powell and the other, titled Wolff v. Rice, filed by David Rice.
