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 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."
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 traffic stop, commonly 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 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.
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.
Consent searches are searches conducted by United States law enforcement after obtaining the voluntary consent of the person being investigated. In some cases, consent may also be obtained from certain third-parties. Searches that are the product of consent are one of several recognized exceptions to the warrant requirement of the Fourth Amendment to the United States Constitution. The prosecution bears the burden of proving that consent was freely and voluntarily given. Courts look to the totality of the circumstances to determine whether consent was freely and voluntarily given.
Search incident to a lawful arrest, commonly known as search incident to arrest (SITA) or the Chimel rule, is a U.S. legal principle that allows police to perform a warrantless search of an arrested person, and the area within the arrestee’s immediate control, in the interest of officer safety, the prevention of escape, and the preservation of evidence.
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. The court ruled that, while it is legal for authorities to target and approach a person based on their behavior, absent more, they cannot detain or search such individual without a warrant.
Virginia v. Moore, 553 U.S. 164 (2008), is a Supreme Court of the United States case that addresses use of evidence obtained by police in a search incident to an arrest if that arrest is later found to be unlawful.
Welsh v. Wisconsin, 466 U.S. 740 (1984), was a 1983 case before the US Supreme Court determining that a warrantless arrest violates the Fourth Amendment protection against unlawful search and seizure.
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.
Berkemer v. McCarty, 468 U.S. 420 (1984), is a decision of the United States Supreme Court which ruled that, in the case of a person stopped for a misdemeanor traffic offense, once they are in custody, the protections of the Fifth Amendment apply to them pursuant to the decision in Miranda v. Arizona 384 U.S. 436 (1966). Previously, some courts had been applying Miranda only to serious offenses.
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."
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.
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.
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.
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.
