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.
Terry v. Ohio, 392 U.S. 1 (1968), was 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 committing, or is about to commit a crime. The court also ruled that the police officer may perform a quick surface search of the person's outer clothing for weapons if they have reasonable suspicion that the person stopped is "armed and presently dangerous." This reasonable suspicion must be based on "specific and articulable facts," and not merely upon an officer's hunch.
A Terry stop in the United States allows the police to briefly detain a person based on reasonable suspicion of involvement in criminal activity. Reasonable suspicion is a lower standard than probable cause which is needed for arrest. When police stop and search a pedestrian, this is commonly known as a stop and frisk. When police stop an automobile, this is known as a traffic stop. If the police stop a motor vehicle on minor infringements in order to investigate other suspected criminal activity, this is known as a pretextual stop. Additional rules apply to stops that occur on a bus.
A traffic stop, colloquially referred to as being pulled over, is a temporary detention of a driver of a vehicle and its occupants by police to investigate a possible crime or minor violation of law.
Reasonable suspicion is a legal standard of proof that in United States law is less than probable cause, the legal standard for arrests and warrants, but more than an "inchoate and unparticularized suspicion or 'hunch'"; it must be based on "specific and articulable facts", "taken together with rational inferences from those facts", and the suspicion must be associated with the specific individual. If police additionally have reasonable suspicion that a person so detained is armed and dangerous, they may "frisk" the person for weapons, but not for contraband like drugs. However, if the police develop probable cause during a weapons frisk, they may then conduct a full search. Reasonable suspicion is evaluated using the "reasonable person" or "reasonable officer" standard, in which said person in the same circumstances could reasonably suspect a person has been, is, or is about to be engaged in criminal activity; it depends upon the totality of circumstances, and can result from a combination of particular facts, even if each is individually innocuous.
Atwater v. Lago Vista, 532 U.S. 318 (2001), was a United States Supreme Court decision which held that a person's Fourth Amendment rights are not violated when the subject is arrested for driving without a seatbelt. The court ruled that such an arrest for a misdemeanor that is punishable only by a fine does not constitute an unreasonable seizure under the Fourth Amendment.
Illinois v. Caballes, 543 U.S. 405 (2005), is a decision by the Supreme Court of the United States in which the Court held that the use of a drug-sniffing police dog during a routine traffic stop does not violate the Fourth Amendment to the U.S. Constitution, even if the initial infraction is unrelated to drug offenses.
Brendlin v. California, 551 U.S. 249 (2007), was a decision by the Supreme Court of the United States that held that all occupants of a car are "seized" for purposes of the Fourth Amendment during a traffic stop, not just the driver.
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.
United States v. Martinez-Fuerte, 428 U.S. 543 (1976), was a decision of the United States Supreme Court that allowed the United States Border Patrol to set up permanent or fixed checkpoints on public highways leading to or away from the Mexican border and that the checkpoints are not a violation of the Fourth Amendment.
Bond v United States, 529 U.S. 334 (2000), was a United States Supreme Court Fourth Amendment case that applied the ruling of Minnesota v. Dickerson to luggage, which held that police may not physically manipulate items without a warrant without violating the Fourth Amendment. The Court ruled that this satisfied the two prong test established by Katz v. United States that, (1) a subjective expectation of privacy in the area in question and (2) that the expectation is reasonable in order for the protections of the Fourth Amendment. In this case, the Court ruled that since the Defendant tried to preserve his privacy by using an opaque bag and that it is reasonable for the Defendant to believe that his bag would not be felt in an "exploratory manner" that the two prongs were satisfied.
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.
Whren v. United States, 517 U.S. 806 (1996), was a unanimous United States Supreme Court decision that "declared that any traffic offense committed by a driver was a legitimate legal basis for a stop."
Pennsylvania v. Mimms, 434 U.S. 106 (1977), is a United States Supreme Court criminal law decision holding that a police officer ordering a person out of a car following a traffic stop and conducting a pat-down to check for weapons did not violate the Fourth Amendment to the United States Constitution.
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.
United States v. Drayton, 536 U.S. 194 (2002), was a case in which the United States Supreme Court clarified the applicability of Fourth Amendment protections to searches and seizures that occur on buses, as well as the function of consent during searches by law enforcement. During a scheduled stop in Tallahassee, Florida, police officers boarded a Greyhound bus as part of a drug interdiction effort and interviewed passengers. After talking to two of the passengers and asking if they could "check [their] person", officers discovered the two passengers had taped several packages of cocaine to their legs. At trial, the passengers argued that officers violated their Fourth Amendment rights against unreasonable searches and seizures because the police engaged in coercive behavior and never informed them that their participation in the drug interdiction efforts was voluntary.
United States v. Sharpe, 470 U.S. 675 (1985), was a legal case in which the Supreme Court of the United States clarified how long police are permitted to stop vehicles as part of an investigatory stop before it violates the Fourth Amendment to the U.S. Constitution.
United States v. Cortez, 449 U.S. 411 (1981), was a United States Supreme Court decision clarifying the reasonable suspicion standard for the investigative stop of a vehicle.
