Amendment to the U.S. Constitution and part of the Bill of Rights that protects people against unreasonable searches and seizures.

The Framers of the Bill of Rights were concerned with the old English practice of issuing general warrants and writs of assistance. These two legal tools authorized searches with few stipulations on searching agents, allowing searches day or night on bare suspicion. Authorized by the monarch, they were valid for the duration of his or her lifetime. They were not required to name a specific person or place but could be stated in more general terms. No oath before a magistrate was necessary to secure a warrant, and probable cause was not required. Everything was left to the discretion of the holder of the warrant. The result was harassment. The colonists were victims of these general warrants and writs of assistance and purposely set out to outlaw them.Search and seizureSearch and seizure

James Madison revised his initial draft of the Fourth Amendment, changing the word “secured” to “secure” and adding the clause “against unreasonable searches and seizures.” Although Madison’s goal was to eliminate general warrants and writs of assistance, scholars believe these alterations made the meaning of the amendment ambiguous. The Fourth Amendment outlaws only unreasonable searches and seizures, logically allowing those deemed reasonable. The Framers envisioned that searches conducted with a warrant, which required specifics such as who is to be searched, what is to be seized, and when, were constitutionally permissible. The warrant clause stipulated what was expected of police when conducting searches. However, left unanswered were the questions of whether there are times when it is reasonable to search without a warrant, what constitutes probable cause, and whether the amendment restricts only police or other governmental agents with searching authority.

The Court in Wolf v. Colorado[case]Wolf v. Colorado[Wolf v. Colorado] (1949) made clear that search warrants had to be supported by probable cause and issued by a neutral and impartial magistrate. However, often searches are conducted without a search warrant.

The Court created a number of exceptions to the search warrant requirementSearch warrant requirement. Using the reasonableness clause of the amendment rather than the warrant provision, the Court rejected the idea of a bright-line rule in favor of a more fact-bound, case-by-case approach. The police do not need a warrant for searches incident to arrest; stop-and-frisk situations; when illegal or stolen items are in plain view during a legal search; administrative, consensual, and border searches; and searches involving exigent circumstances such as automobile searches.

When an individual is arrested on probable cause, a police officer is permitted to conduct a warrantless search of the person. This exception to the warrant requirement, search incident to arrest, rests on the understanding that the arresting officer must have the power to disarm the accused and preserve any evidence. Protecting the officer’s safety and retaining probative evidence is reasonable. The officer may search not only the person but the areas of immediate control. In Chimel v. California[case]Chimel v. California[Chimel v. California] (1969), the Court reasoned that the scope of a search incident to arrest included wherever the arrestee might reach to grab a weapon or piece of evidence.

If in the course of a valid search, an officer comes on stolen or illegal items in plain view, they may be seized and used as evidence. This inadvertent windfall is permissible and reasonable under the Fourth Amendment as long as the officer happens on the evidence in the course of conducting a legal search. Related is the plain feel exception. In Minnesota v. Dickerson[case]Minnesota v. Dickerson[Minnesota v. Dickerson] (1993), the Court held that if an officer feels what seems to be contraband or evidence of a crime when patting down the outside of a suspect’s clothing, the items can be seized.

In Terry v. Ohio[case]Terry v. Ohio[Terry v. Ohio] (1968), the Court allowed for searches on the street that did not meet the standard of probable cause. In this case, it upheld the brief detention of a suspect for weapons on the grounds of reasonable suspicion rather than probable cause. Only a limited frisk was permitted with the lowered standard of cause. If the pat-down yielded a basis for an arrest, however, a full search incident to arrest could follow.Stop and frisk rule

The Court has applied the Fourth Amendment to the increasing problems arising in a mobile society. Planes, buses, trains, and boats all raise exigency concerns because of the highly mobile nature of the place to be searched and the futility of the police in executing search warrants on moving objects. The most common exigent circumstance is created by the automobileAutomobile searches. As early as 1925 in Carroll v. United States[case]Carroll v. United States[Carroll v. United States], the Court made clear that the automobile would not be afforded the same level of privacy rights protection as an individual’s home or person. Stopping an automobile and searching it on the street without a warrant was reasonable. However, the particulars of the car have generated a volume of litigation aimed at answering questions such as whether the police can lawfully open the glove box, the trunk, or containers in the automobile or search the driver, passengers, and their personal items. Given the lower expectation of privacy in automobiles, the Court in Michigan Department of State Police v. Sitz[case]Michigan Department of State Police v. Sitz[Michigan Department of State Police v. Sitz] (1990) allowed roadblocks to briefly stop all drivers to catch those driving under the influence of drugs and alcohol.

Employees of other governmental agencies, such as housing, fire, health, welfare, and safety inspectors, also have searching capabilities. These agents have a lesser standard than probable cause and often invoke an element of surprise, such as unannounced inspections of restaurants. Related to these types of searches are those to ensure safety in the workplace or school by drug-testing employees and students. In National Treasury Employees Union v. Von Raab[case]National Treasury Employees Union v. Von Raab[National Treasury Employees Union v. Von Raab] (1989), the Court upheld suspicionless mandatory urinalysis testing for promotion on the grounds of safety (the employees would have access to firearms and secure information). By 1995 in Vernonia School District v. Acton[case]Vernonia School District v. Acton[Vernonia School District v. Acton], the Court upheld the right to drug-test all student athletes without requiring suspicion of individuals.

The courts have long recognized that individuals and items entering the United States may be searched at the international border without warrant or probable cause. The Court has placed some limits on these searches, such as the level of intrusion. Strip searches, for example, must be justified by real suspicion. In an attempt to stop the influx of illegal drugs, law enforcement developed the drug courier profile, a composite of variables that indicates the likelihood an individual is trafficking drugs. In United States v. Sokolow[case]Sokolow, United States v.[Sokolow, United States v.] (1989), the Court upheld the use of the profile as a basis for detaining and searching individuals both at the border and within the continental United States.

In Schneckloth v. Bustamonte[case]Scheneckloth v. Bustamonte[Scheneckloth v. Bustamonte] (1973), the Court acknowledged the use of consent searches, noting that individuals may waive their Fourth Amendment rights and allow a search without a warrant or probable cause. The key to the validity of such searches is that they must be voluntary; an individual must knowingly and freely consent to be searched. The waiver must be uncoerced, given without trickery or fear or promise of reward. Consent can be withdrawn at any time, and a refusal to give consent cannot then be used to establish probable cause.

The Fourth Amendment also applies to wiretapping and other forms of police surveillance. The Court in Katz v. United States[case]Katz v. United States[Katz v. United States] (1967) reasoned that a person’s expectation of privacy includes the seizure of intangible items such as words.

The Fourth Amendment describes the right to be secure against unreasonable searches and seizures without mentioning a remedy. The common-law remedy for search and seizure violations was a suit of trespass. This was used until Weeks v. United States[case]Weeks v. United States[Weeks v. United States] (1914) when the Court adopted the exclusionary rule, which excludes illegally seized evidence from trials. The twofold purpose of the rule is to preserve the integrity of the judiciary and deter police misconduct. Weeks mandated the application of the exclusionary rule to searching agents of the federal government. In 1949 in Wolf, the Court incorporated the Fourth Amendment, thereby requiring states not to abridge the search and seizure rights of their citizens, yet allowing them to choose the remedy. This choice was eliminated in Mapp v. Ohio[case]Mapp v. Ohio[Mapp v. Ohio] (1961) when the Court incorporated the remedy of exclusion from trials for all Fourth Amendment violations, by either state or federal officials.

Mapp’s scope was limited by the Court. In Linkletter v. Walker[case]Linkletter v. Walker[Linkletter v. Walker] (1965), the Court refused to apply the exclusionary rule retroactively. The exclusion remedy was limited in scope so that it did not include grand jury proceedings in United States v. Calandra[case]Calandra, United States v.[Calandra, United States v.] (1974). The Court ruled in United States v. Havens[case]Havens, United States v.[Havens, United States v.] (1980) that illegally seized evidence could be used to impeach the credibility of the defendant at trial and in Nix v. Williams[case]Nix v. Williams[Nix v. Williams] (1984) that it could also be admitted into evidence if the police would have inevitably discovered the evidence by lawful means. In 1984 in United States v. Leon[case]Leon, United States v.[Leon, United States v.] and Massachusetts v. Sheppard, the Court allowed the use of illegally obtained evidence if the police error was made in objective good faith. The Court was unwilling to exclude reliable probative evidence when the error made by the police was unintentional and made in the course of attempting to follow the law.

• Otis H. Stephens and Richard A. Glenn’s Unreasonable Searches and Seizures: Rights and Liberties Under the Law (Santa Barbara, Calif.: ABC-Clio, 2004) covers the subject of Fourth Amendment jurisprudence through two centuries of American history. Samuel Dash’s The Intruders: Unreasonable Searches and Seizures from King John to John Ashcroft (New Brunswick, N.J.: Rutgers University Press, 2004) takes an even deeper historical approach, tracing protection against unreasonable searches back to early English history. Paula Franklin’s The Fourth Amendment (New York: Silver Burdett Press, 2001) describes the origins of the Fourth Amendment as a check on police abuses. William W. Greenhalgh’s The Fourth Amendment Handbook: A Chronological Survey of Supreme Court Decisions (2d ed. Chicago: Criminal Justice Section, American Bar Association, 2003) is a professional handbook for lawyers. Another good historical treatment of the Fourth Amendment is Nelson B. Lasson’s The History and Development of the Fourth Amendment to the United States Constitution (Baltimore, Md.: Johns Hopkins University Press, 1937). Several classic and often cited works about the Fourth Amendment are Jacob W. Landynski’s Search and Seizure and the Supreme Court (Baltimore, Md.: Johns Hopkins University Press, 1966), Wayne LaFave’s Search and Seizure: A Treatise on the Fourth Amendment (Mineola, N.Y.: Foundation Press, 1978), Erwin N. Griswold’s Search and Seizure: A Dilemma of the Supreme Court (Lincoln: University of Nebraska Press, 1975), and Telford Taylor’s Two Studies in Constitutional Interpretation (Columbus: Ohio State University Press, 1969). A general treatment of Fourth Amendment rights can be found in David M. O’Brien’s Constitutional Law and Politics: Civil Rights and Liberties (6th ed. 2 vols. New York: W. W. Norton, 2005). Some law review articles debating the policy implications of the Fourth Amendment and its remedy are Anthony Amsterdam’s “The Supreme Court and the Rights of Suspects in Criminal Cases,” New York University Law Review 45 (1970): 785, Yale Kamisar’s “Is the Exclusionary Rule an‘Illogical’ or ‘Unnatural’ Interpretation of the Fourth Amendment?” Judicature 62 (1978): 67, and Malcolm Wiley’s “Constitutional Alternatives to the Exclusionary Rule,” South Texas Law Journal 23 (1982): 531. Warren E. Burger expressed his views on the Fourth Amendment in “Who Will Watch the Watchman?” American University Law Review 14 (1964): 1.

Automobile searches

Bill of Rights

Carroll v. United States

Chimel v. California

Exclusionary rule

Leon, United States v.

Mapp v. Ohio

Search warrant requirement

Stop and frisk rule

Weeks v. United States

Wolf v. Colorado