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 decision of the Supreme Court of the United States in which the Court ruled that it is not unconstitutional 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 it is not a violation of the Fourth Amendment to the U.S. Constitution's prohibition on unreasonable searches and seizures when a police officer stops a suspect on the street and questions him or her even without probable cause to arrest, 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 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.
City of Indianapolis v. Edmond, 531 U.S. 32 (2000), was a case in which the Supreme Court of the United States limited the power of law enforcement to conduct suspicionless searches, specifically, using drug-sniffing dogs at roadblocks. 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. This decision stated that the power was limited to situations in which the search was "designed to serve special needs, beyond the normal need for law enforcement."
Illinois v. Caballes, 543 U.S. 405 (2005), was a United States Supreme Court case in which the Court held that the Fourth Amendment is not violated when the use of a drug-sniffing dog during a routine traffic stop does not unreasonably prolong the length of the stop.
Florida v. Bostick, 501 U.S. 429 (1991), was a United States Supreme Court case that overturned a per se rule imposed by the Florida Supreme Court that held consensual searches of passengers on buses were always unreasonable. The Court ruled that the fact that the search takes place on a bus is one factor in determining whether a suspect feels free to decline the search and walk away from the officers.
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.
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.
Welsh v. Wisconsin, 466 U.S. 740 (1984), was a 1983 case before the US Supreme Court determining whether a warrantless arrest violates the Fourth Amendment protection against unlawful search and seizure.
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.
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.
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."
Soldal v. Cook County, 506 U.S. 56 (1992), was a United States Supreme Court case in which the Court held that a seizure of property like that which occurs during an eviction, even absent a search or an arrest, implicates the Fourth Amendment. The Court also held that the Amendment protects property as well as privacy interests, in both criminal as well as civil contexts. Finally, saying that "certain wrongs affect more than a single right", the Court left open the possibility that the Fourteenth Amendment's protections against deprivation of property without due process of law may also be implicated.
Missouri v. McNeely, 569 U.S. 141 (2013), was a case decided by United States Supreme Court, on appeal from the Supreme Court of Missouri, regarding exceptions to the Fourth Amendment to the United States Constitution under exigent circumstances. The United States Supreme Court ruled that police must generally obtain a warrant before subjecting a drunken-driving suspect to a blood test, and that the natural metabolism of blood alcohol does not establish a per se exigency that would justify a blood draw without consent.
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.
Navarette v. California, 572 U.S. 393 (2014), was a case in which the United States Supreme Court clarified when police officers may make arrests or conduct temporary detentions based on information provided by anonymous tips. In 2008, police in California received a 911 call that a pickup truck was driving recklessly along a rural highway. Officers spotted a truck matching the description provided in the 911 call and followed the truck for five minutes, but did not observe any suspicious behavior. Nevertheless, officers conducted a traffic stop and discovered 30 pounds (14 kg) of marijuana in the truck. At trial, the occupants of the car argued that the traffic stop violated the Fourth Amendment of the United States Constitution, because the tip was unreliable, and officers did not personally observe criminal activity. Writing for a majority of the Court, Justice Clarence Thomas held that the 911 call was reliable, and that officers need not personally observe criminal activity when acting upon information provided by an anonymous 911 call.
Birchfield v. North Dakota, 579 U.S. ___ (2016), was 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.
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.
