The Fourth Amendment
Unreasonable Search and Seizure
The Fourth Amendment to the United States Constitution prohibits the federal government from conducting "unreasonable searches and seizures." In general, this means police cannot search a person without a warrant or probable cause. It also applies to arrests and the collection of evidence.
However, what is "reasonable" is a question the U.S. Supreme Court has grappled with for more than two hundred years. Additionally, technological advancements have expanded the government's ability to search and surveil people, raising the question of what constitutes a "search" under the Fourth Amendment.
This section covers essential concepts related to the Fourth Amendment, including the constitutional right to privacy, search warrants, and the protection of personal property. It also discusses several landmark Supreme Court decisions on these topics.
What the Fourth Amendment Says
The Fourth Amendment is often viewed as two clauses. The first reads:
"The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated..."
The second clause states:
"...and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized."
What the Fourth Amendment Means
The Fourth Amendment reflects the Framers' intent to avoid the perceived unjust searches and seizures they experienced under English rule. It prevents the federal and state governments from conducting "unreasonable searches and seizures."
As the National Constitution Center notes, "The idea is that to avoid the evils of general warrants, each search or seizure should be cleared in advance by a judge, and that to get a warrant the government must show 'probable cause'—a certain level of suspicion of criminal activity—to justify the search or seizure." In doing so, the Fourth Amendment protects the "full enjoyment of the rights of personal security, personal liberty, and private property."
The Fourth Amendment requires the government to obtain a warrant based on probable cause to conduct a legal search and seizure. However, the Supreme Court has carved out numerous exceptions to the warrant requirement, as explained below.
The Supreme Court has issued many landmark decisions regarding the Fourth Amendment and its effect on criminal procedure. Its decisions cover many different topics concerning the Fourth Amendment, including the following:
Frequently Asked Questions
This section answers frequently asked questions about the Fourth Amendment.
What is a “search” under the Fourth Amendment?
Under the Fourth Amendment, a search occurs when a government agent (e.g., a police officer) intrudes into a space in which someone has a reasonable expectation of privacy.
As the Supreme Court noted in an 1886 case, a search isn't just the "breaking of his doors and the rummaging of his drawers." Instead, a search occurs when the government invades someone of their "indefeasible right of personal security, personal liberty, and private property." (Boyd v. United States (1886)).
There are no bright-line rules for whether someone's expectation of privacy is "reasonable." Instead, whether someone has a "reasonable" expectation of privacy depends upon the totality of the circumstances.
For example, a person has a reasonable expectation of privacy in their home. You generally do not have a reasonable expectation of privacy in a public park or on the sidewalk.
What is a “seizure” under the Fourth Amendment?
A seizure refers to an arrest of a person or a seizure of property.
What constitutes an illegal search and seizure?
Generally, a search or seizure is illegal under the Fourth Amendment if it occurs without consent, a warrant, or probable cause to believe a crime has been committed. However, there are several exceptions to the warrant requirement.
What is required for a search warrant?
To obtain a search warrant, a law enforcement officer must request one from a judge. They must make their request in good faith and base it on reliable information that shows probable cause to search. A judge must sign and issue the warrant. The warrant must state the area law enforcement intends to search and the items or people they seek.
What is probable cause?
A law enforcement officer establishes probable cause if a "prudent man" who knew the facts and circumstances known to the officer would believe that a suspect committed a criminal offense.
However, in certain situations, law enforcement may perform a search when they have a reasonable suspicion of criminal activity. This "reasonable suspicion" falls short of the standard needed to establish probable cause. For example, "stop-and-frisk" searches are one of the exceptions to the warrant requirement.
If the police have a warrant, can they search wherever they want?
No. Police can only search the area listed on the search warrant. For example, if they had a warrant to search only your car, they could not also search your home. However, they can search outside the warrant's scope and seize other items if they are in plain view. They can also act to prevent the destruction of evidence.
Historical Background
The states ratified the Fourth Amendment in 1791 as part of the Bill of Rights. As noted above, the Framers proposed the Fourth Amendment due to their experience with the English Crown's use of its power to search and seize people and property.
Freedom against governmental searches and seizures originated in early British law and policy. As the Constitution Annotated notes, it derives from the famous maxim, "Every man's house is his castle." English legal scholars and practitioners like Sir Edward Coke emphasized this idea in early cases and legal theories.
Despite this, English royalty abused their powers to issue general warrants and writs of assistance.
General warrants allowed agents of the Crown to search people and places without cause.
The Crown used writs of assistance in the American colonies to search for goods upon which owners had allegedly not paid taxes. This allowed the Crown to combat smuggling. The Constitution Annotated describes writs of assistance as "general warrants authorizing the bearer to enter any house or other place to search for and seize prohibited and uncustomed goods, and command all subjects to assist in these endeavors."
In England, a series of civil cases played a role in Congress' eventual development of the Fourth Amendment. Two of the most important cases were Wilkes v. Wood (1763) and Entick v. Carrington (1765). In both cases, the courts held that general warrants violated English common law.
Another court case in the United States may have sparked the American Revolution. After King George II died in 1760, his writs of assistance expired. This prompted the Crown to issue a new wave of writs.
James Otis, a lawyer from Massachusetts, challenged the issuance of the writs in 1761. He argued that the "authorizing statutes were invalid because they conflicted with England's constitution."
Otis lost his case, and the Crown issued and used the writs. However, Otis' challenges to the writs were "much cited in the colonies not only on the immediate subject but also with regard to judicial review." John Adams and others attributed Otis' case to potentially leading to the Revolutionary War.
In 1787, delegates from each state met in Philadelphia for the Constitutional Convention. Although the U.S. Constitution did not initially contain the Fourth Amendment, Congress began working on several amendments soon after the Constitution's ratification.
James Madison, a Virginia congressman, was instrumental in crafting the Fourth Amendment's language. The states ratified it in 1791.
Like the other amendments in the Bill of Rights, the Fourth Amendment used to apply only to the federal government. In other words, it did not apply to state police or government agents. However, in Mapp v. Ohio (1961), the Supreme Court held that the Fourth Amendment rights apply in both state and federal courts via the Fourteenth Amendment's doctrine of incorporation.
Important Fourth Amendment Supreme Court Decisions
The Supreme Court's decisions concerning the Fourth Amendment are important in criminal law and procedure today. For example, the decisions have clarified the situations in which a warrantless search is legal, what constitutes a search, and what happens if the government conducts an illegal search and seizure. This section describes some of these cases.
The Reasonable Expectation of Privacy
Katz v. United States (1967) is the leading case on Fourth Amendment searches. There, law enforcement agents installed a recording device (a "wiretap") in a public telephone booth. They did so to learn about a suspect's illegal gambling activity. The government installed the wiretap without obtaining a warrant.
The Supreme Court ruled that installing the wiretap constituted a search under the Fourth Amendment. The Court's analysis of what constitutes a "search" under the Fourth Amendment has informed all subsequent decisions regarding the issue. The Court also introduced the concept of a "reasonable expectation of privacy" in its opinion.
Writing for the majority, Justice Potter Stewart wrote that the Fourth Amendment "protects people, not places." Therefore, whatever a person "knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection." Justice Stewart continued by writing that "what he seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected."
Applying this reasoning to the case at hand, Justice Stewart wrote that the defendant sought to exclude "the uninvited ear" by entering the phone booth. The defendant, Justice Stewart wrote, "did not shed his right to do so simply because he made his calls from a place where he might be seen."
Justice John Marshall Harlan agreed with the majority. He wrote a concurring opinion that became highly influential for its two-part analysis of Fourth Amendment searches. His two-part test is as follows:
The person must exhibit "an actual (subjective) expectation of privacy," and
That the expectation "be one that society is prepared to recognize as 'reasonable.'"
The Court's decision in Katz provided the basis for its analysis of subsequent Fourth Amendment cases. The ruling also led to the requirement that law enforcement must obtain a warrant before conducting surveillance that violates a reasonable expectation of privacy.
The Katz decision marked a significant shift in Fourth Amendment jurisprudence. It focused on protecting privacy rather than property rights or physical intrusion and established that the Fourth Amendment "protects people, not places."
The Exclusionary Rule
In Mapp v. Ohio (1961), the Court ruled that the Fourth Amendment's protections against unreasonable searches and seizures apply to state courts through the Fourteenth Amendment. It also held that the exclusionary rule also applies to state courts.
Authorities suspected Dollree Mapp of harboring a fugitive involved in a bombing. Police officers forced their way into her home without a proper search warrant.
During the search, the police found obscene materials which violated Ohio's laws. Law enforcement arrested Mapp for possessing the materials. She was eventually convicted regarding the materials.
Mapp contested her conviction. She argued that the evidence obtained during the search was inadmissible because authorities obtained it without a warrant.
The Supreme Court held that evidence obtained in violation of the Fourth Amendment is inadmissible in state courts. This ruling extended the exclusionary rule, previously applied only to federal courts, to the states. The exclusionary rule prevents courts from considering illegally obtained evidence.
The Court reasoned that the exclusionary rule is essential to make the Fourth Amendment effective. It also deters law enforcement officers from conducting illegal searches and seizures. By applying the exclusionary rule to the states, the Court aimed to ensure a uniform standard of constitutional rights.
Mapp serves as a crucial check on police powers. The case was pivotal in reinforcing the Fourth Amendment's protections by applying the exclusionary rule to the states, ensuring that the prosecution cannot use illegally obtained evidence in court.
Warrantless Searches
The Court has gone back and forth about the scope of the warrant requirement. A few notable decisions include:
In 1947, the Court held that law enforcement had to obtain a search warrant "whenever reasonably practicable."
In 1950, the Court ruled that the test was not whether it was reasonably practicable to obtain a warrant but whether the search itself was reasonable. If the search was reasonable, it was legal, and no warrant was necessary.
In 1968, the Court reemphasized the warrant requirement. The Court wrote, "the police must, whenever practicable, obtain advance judicial approval of searches and seizures through a warrant procedure."
In the 1970s, the Court generally held that warrantless searches were per se unreasonable (although it did carve out several exceptions).
In the early 1990s, the Court reverted back to the idea that the legality of a search depends upon whether it was reasonable. In a 1996 case, the Court ruled that whether a search is reasonable "is measured in objective terms by examining the totality of the circumstances, and the Court had consistently eschewed bright-lines rules."
Law enforcement may search and/or seize someone or something without a warrant in several circumstances. These include the following:
When they arrest someone on suspicion of committing a felony, and the arrest was made in a public place
In connection with a lawful arrest
During a traffic stop based on reasonable suspicion
During a traffic stop based on the "plain view" exception
When they stop someone suspected of committing ongoing criminal activity
In an emergency ("exigent circumstances"), like when they are in hot pursuit of a fleeing suspect, or to prevent the destruction of evidence
When they stop a vehicle as part of a roadside checkpoint
When they search someone in good faith, but a court later rules the warrant they had was invalid
Read When the Fourth Amendment Applies for more information about warrantless searches.
Digital Privacy
In Riley v. California (2014), the United States Supreme Court addressed whether the search incident to arrest exception extended to digital information on a cell phone.
After law enforcement arrested David Riley, they searched his smartphone without a warrant. They discovered incriminating evidence during the search. Riley contested the search, arguing that it violated his Fourth Amendment rights.
The Supreme Court unanimously held that the warrantless search and seizure of a cell phone's digital contents during an arrest is unconstitutional. The Court recognized that cell phones are not just physical objects. They contain vast amounts of personal data. This, the Court held, is fundamentally different from other items on an arrestee.
Chief Justice Roberts noted that modern cell phones hold "the privacies of life." He argued that this warranted robust protection against government intrusion.
The ruling underscored law enforcement's need to obtain a warrant for digital information. It also showed the Court's ability to apply traditional Fourth Amendment principles to the digital age.
Related Constitutional Rights
The Fourth Amendment is one of several amendments included in the Bill of Rights that promote due process and safeguard the rights of the people against law enforcement officials. For more information, read the following articles:
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