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.
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.
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.
City of Indianapolis v. Edmond, 531 U.S. 32 (2000), was a United States Supreme Court case in which the Court held, 6–3, that police may not conduct vehicle searches, specifically ones involving drug-sniffing police dogs, at a checkpoint or roadblock without reasonable suspicion. In the case, the Indianapolis Police Department was conducting warrantless searches of vehicles, without individualized suspicion, for the purpose of "general crime control". Previous Supreme Court decisions had given the police power to create roadblocks for the purposes of border security and removing drunk drivers from the road, but in this decision, the Court limited police power, holding that the search can only occur if it was designed to serve special needs, beyond the normal need for law enforcement.
Illinois v. Caballes, 543 U.S. 405 (2005), was a decision by the Supreme Court of the United States in which the Court held, 6–2, 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.
United States v. Arvizu, 534 U.S. 266 (2002), is a case in which the Supreme Court of the United States unanimously reaffirmed the proposition that the Fourth Amendment required courts to analyze the reasonableness of a traffic stop based on the totality of the circumstances instead of examining the plausibility of each reason an officer gives for stopping a motorist individually.
A random checkpoint is a military and police tactic. In a military context, checkpoints involve the setup of a hasty roadblock by mobile truck- or armored vehicle-mounted infantry to disrupt unauthorized or unwanted movement or military activity and to check for valid identification and search for contraband, fugitives, or weapons that are not permitted in civilian hands. Random checkpoints are set up to achieve surprise, as opposed to known permanently located checkpoints, which suspects could circumvent. They are often established in locations where they cannot be observed by approaching traffic until it is too late to withdraw and escape without being observed.
Michigan Dept. of State Police v. Sitz, 496 U.S. 444 (1990), was a United States Supreme Court case involving the constitutionality of police sobriety checkpoints. The Court held 6-3 that these checkpoints met the Fourth Amendment standard of "reasonable search and seizure."
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. The doctrine is not regarded as an exception to the Fourth Amendment, but rather to its requirement for a warrant or probable cause. Balanced against the sovereign's interests at the border are the Fourth Amendment rights of entrants. Not only is the expectation of privacy less at the border than in the interior, the Fourth Amendment balance between the interests of the government and the privacy right of the individual is also struck much more favorably to the government at the border. This balance at international borders means that routine searches are "reasonable" there, and therefore do not violate the Fourth Amendment's proscription against "unreasonable searches and seizures".
Illinois v. Lidster, 540 U.S. 419 (2004), was a case in which the Supreme Court of the United States ruled that the Fourth Amendment permits the police to use a roadblock to investigate a traffic incident.
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. Brignoni-Ponce, 422 U.S. 873 (1975), was the case in which the Supreme Court determined it was a violation of the Fourth Amendment for a roving patrol car to stop a vehicle solely on the basis of the driver appearing to be of Mexican descent. A roving patrol car must have articulable facts that allow for an officer to have a reasonable suspicion that the person is carrying illegal aliens beyond their ethnicity. The Court handed down a 9–0 decision that affirmed the Circuit Court's ruling in the case.
The United States Border Patrol operates 71 traffic checkpoints, including 33 permanent traffic checkpoints, near the Mexico–United States border. The stated primary purpose of these inspection stations is to deter illegal immigration and smuggling activities. After the September 11 attacks in 2001, they took on the additional role of terrorism deterrence. These checkpoints are located between 25 and 75 miles of the Mexico–United States border along major U.S. highways; near the southern border of the contiguous United States. Their situation at interior locations allow them to deter illegal activities that may have bypassed official border crossings along the frontier. The checkpoints are divided among nine Border Patrol sectors. There are a number of these checkpoints near the northern border of the contiguous U.S. as well, within 100 miles (160 km) of the Canada–U.S. border.
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."
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.
Florida v. Jardines, 569 U.S. 1 (2013), was a United States Supreme Court case which resulted in the decision that police use of a trained detection dog to sniff for narcotics on the front porch of a private home is a "search" within the meaning of the Fourth Amendment to the United States Constitution, and therefore, without consent, requires both probable cause and a search warrant.
The "special needs" exception is an exception to the Fourth Amendment’s general requirement that government searches be supported by a warrant and probable cause. The exception applies when (1) the government conducts programmatic searches that are primarily aimed at advancing some special need other than criminal law enforcement, and (2) the government’s search program is reasonable given the balance of public and private interests.
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.
