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.
A search warrant is a court order that a magistrate or judge issues to authorize law enforcement officers to conduct a search of a person, location, or vehicle for evidence of a crime and to confiscate any evidence they find. In most countries, a search warrant cannot be issued in aid of civil process.
In United States criminal law, probable cause is the standard by which police authorities have reason to obtain a warrant for the arrest of a suspected criminal or the issuing of a search warrant. There is no universally accepted definition or formulation for probable cause. One traditional definition, which comes from the U.S. Supreme Court's 1964 decision Beck v. Ohio, is when "whether at [the moment of arrest] the facts and circumstances within [an officer's] knowledge and of which they had reasonably trustworthy information [are] sufficient to warrant a prudent [person] in believing that [a suspect] had committed or was committing an offense."
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.
False arrest, Unlawful arrest or Wrongful arrest is a common law tort, where a plaintiff alleges they were held in custody without probable cause, or without an order issued by a court of competent jurisdiction. Although it is possible to sue law enforcement officials for false arrest, the usual defendants in such cases are private security firms.
United States v. Place, 462 U.S. 696 (1983), is a decision by the Supreme Court of the United States in which the Court held that it does not violate the Fourth Amendment to the U.S. Constitution for a trained police dog to sniff of a person's luggage or property in a public place.
Reasonable suspicion is a legal standard of proof in United States law that 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.
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.
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.
Carroll v. United States, 267 U.S. 132 (1925), was a decision by the United States Supreme Court that upheld the warrantless searches of an automobile, which is known as the automobile exception. The case has also been cited as widening the scope of search.
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.
New York v. Belton, 453 U.S. 454 (1981), was a United States Supreme Court case in which the Court held that when a police officer has made a lawful custodial arrest of the occupant of an automobile, the officer may, as a contemporaneous incident of that arrest, search the passenger compartment of that automobile. Therefore, Belton extended the so-called "Chimel rule" of searches incident to a lawful arrest, established in Chimel v. California (1969), to vehicles. The Supreme Court sought to establish bright line rules to govern vehicle search incident to eliminate some confusion in the cases.
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.
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."
Arizona v. Johnson, 555 U.S. 323 (2009), is a United States Supreme Court case in which the Court held, by unanimous decision, that police may conduct a pat down search of a passenger in an automobile that has been lawfully stopped for a minor traffic violation, provided the police reasonably suspect the passenger is armed and dangerous.
Ornelas v. United States, 517 U.S. 690 (1996), was a case decided by the Supreme Court of the United States that held that appellate courts should review probable cause determinations for warrantless searches de novo.
Steagald v. United States, 451 U.S. 204 (1981), is a United States Supreme Court case which held that, based on the Fourth Amendment, a police officer may not conduct a warrantless search of a third party's home in an attempt to apprehend the subject of an arrest warrant, absent consent or exigent circumstances.
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.
Devenpeck v. Alford, 543 U.S. 146 (2004), was a United States Supreme Court decision dealing with warrantless arrests and the Fourth Amendment. The Court ruled that even if an officer wrongly arrests a suspect for one crime, the arrest may still be "reasonable" if there is objectively probable cause to believe that the suspect is involved in a different crime.
