Fourth Amendment

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Date: 2008
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Fourth Amendment

The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, 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.

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Ratification Facts


Submitted by Congress to the states on September 25, 1789, along with the other nine amendments that comprise the Bill of Rights.


Ratified by the required three-fourths of states (eleven of fourteen) on December 15, 1791. Declared to be part of the Constitution on December 15, 1791.

Ratifying states:

New Jersey, November 20, 1789; Maryland, December 19, 1789; North Carolina, December 22, 1789; South Carolina, January 19, 1790; New Hampshire, January 25, 1790; Delaware, January 28, 1790; New York, February 24, 1790; Pennsylvania, March 10, 1790; Rhode Island, June 7, 1790; Vermont, November 3, 1791; Virginia, December 15, 1791 (amendment adopted).

Wiretaps, drug-sniffing dogs, random locker searches, drug raids and thermal imagers are just some of the tools police and other authorities use to gather evidence of wrongdoing and fight crime in the United States. The Fourth Amendment seeks to balance the civic need for effective law enforcement with the individual’s rights to privacy and property by prohibiting police from “unreasonably” conducting searches or seizing property as evidence.

Probable Cause and the Particularity Requirement

Before conducting a legal search, a police officer must usually obtain a warrant from a judge or other employee of the court. A warrant is a court document that gives an officer certain limited powers to search for evidence or make arrests.

According to the Fourth Amendment, there are two main conditions that must be met for a warrant to be legal. First, an officer must convince a judge that there is a good reason to issue a warrant, which is called showing probable cause. Second, the warrant must be very specific, which is called the particularity requirement.

An officer shows probable cause by presenting information that would convince a “reasonable person” that a crime has been committed and that the person to be searched is probably connected to the crime. To meet the particularity requirement, a warrant must list exactly who and what is to be searched and what type of evidence the officer hopes to find.

Though it establishes some specific conditions for legal searches and the collection of evidence, the wording of the Fourth Amendment leaves plenty of room for interpretation. For example, the Fourth Amendment prohibits “unreasonable searches and seizures” but does not define “unreasonable.” It has been left to the courts to determine the meaning of “unreasonable.” Some of the questions that have arisen regarding enforcement of the Fourth Amendment include the following:

  1. What is an “unreasonable” search?
  2. What constitutes probable cause?
  3. Can an officer seize evidence not listed on a warrant?
  4. Do all searches require a warrant?
  5. Can evidence obtained during an unconstitutional search be used in court?
  6. Are students protected by the Fourth Amendment at school?

There are no simple answers to these questions. The Supreme Court has heard hundreds of cases involving such Fourth Amendment issues and used various interpretations of the amendment to establish specific rules concerning police searches and the seizure of property.

Protecting the “Comforts of Society”

In the early 1300s, Britain’s king began granting his officials general warrants, which they could use to search any home they wished, seize any property they saw fit, and arrest anyone based on what they found. These warrants, once issued, lasted until the death of the king or queen who issued them. Often these warrants were used to harass people who practiced unpopular religions or who disagreed with the government’s policies.

In 1762 the government of King George III (1738–1820) used general warrants to break into the homes and offices of authors, printers, and publishers suspected of being critical of the king. The agents ransacked the suspects’ possessions and seized their papers. The victims of the raids sued the government for illegal trespass, but officials argued that they had legal warrants for the searches.

Two of the cases, Wilkes v. Wood (1763) and Entick v. Carrington (1765), were heard by the same judge, Lord Camden. Camden ruled that the warrants in the cases were not based on facts that justified the searches. In other words, they lacked probable cause.

He also ruled that the warrants were not specific enough, because they ordered the seizure of all of the suspects’ papers, rather than those that might have been part of a crime. Such broad warrants, Camden wrote, undermined “all the comforts of society.” As a result of Camden’s ruling, the men who had been wrongly searched or imprisoned were allowed to sue the government.

Writs of Assistance in America

In Britain’s American colonies, customs officials and tax collectors had used general warrants, known as writs of assistance, to conduct random searches since the late seventeenth century. With warrant in hand, British officials could seize any property and arrest anyone based only on suspicions. In other words, agents in the colonies, like their counterparts in England, had never been required to show probable cause or to specify what they were searching for.

Because warrants were good only during the lifetime of the king who issued them, when King George II (1683–1760) died, all writs given out under his authority became void. Government officials wishing to conduct searches in the colonies had to obtain fresh warrants under the authority of the new king, George III.

In 1761 merchants in Boston, Massachusetts, went to court to stop new warrants from being granted (Paxton’s Case.) The merchants’ attorney, James Otis Jr. (1725–1783), denounced the writs as “the worst instrument of arbitrary power …. that ever was found in our English law book” because they placed “the liberty of every man in the hands of every petty officer.”

Otis, James In 1761, attorney James Otis Jr. argued that Boston need a fairer process of issuing warrants. MPI/Getty Images.

Otis argued for a fairer process of issuing warrants in which officers would be given the right “to search certain houses” for particular evidence. Warrants, he argued, should only be granted after the official swore under oath “that he suspects such goods to be concealed in those very places he desires to search.”

The merchants lost the case, and British officials continued to use general warrants to conduct random searches in the colonies. But Otis’s fiery arguments against excessive government intrusion aroused colonists’ growing revolutionary spirit. After the trial, angry crowds often interfered with customs and revenue agents attempting to enforce general warrants, while some local magistrates (judges) declined to give out the writs of assistance.

Establishing the People’s Rights

Growing tension between Great Britain and the American colonies led to the American Revolutionary War (1775—83), in which the colonies separated from the British Empire. The newly independent colonies (now states) formed a loose alliance with each other under the Articles of Confederation in 1781. Then in 1788, the states adopted the U.S. Constitution (see chapter one), which established a much stronger central government.

But because nothing in the new Constitution spelled out the people’s rights, many worried that the new government might take the very liberties the colonists had fought Great Britain to win. In response to this concern, a number of amendments (additions) defining different rights were proposed to the Constitution. The first ten amendments to be agreed upon by the states are known as the Bill of Rights (see chapter one).

James Madison (1751–1836), a Virginia lawyer who later became the fourth president of the United States and history records as “the Father of the Bill of Rights,” wrote the Fourth Amendment, using Otis’s ideas from Paxton’s Case and from Camden’s ruling in Entick v. Carrington. With the memory of abusive British searches still fresh in the people’s minds, the amendment was officially ratified by the states on December 15, 1791.

Interpreting the Fourth Amendment

The Supreme Court, as established by the Constitution (see chapter one), is the highest court in the United States. Congress (the law-making branch of the United States government) decides how many judges sit on the Court. The Court originally consisted of six justices (judges) but included nine justices after 1869. Interestingly, the U.S. Constitution does not specify the number of justices; it only calls for a Supreme Court and mentions a chief justice. Congress determines the makeup of the Supreme Court. A justice may write an opinion supporting either side of a given case, but the Court’s final ruling is left to a simple vote of all the justices.

The justices typically hear appeals of cases first heard by lower courts. (An appeal is a legal request to reconsider a court’s ruling.) The Supreme Court is the final interpreter of all federal laws, including the constitutional amendments. The Fourth Amendment, which has played an important and changing role in criminal justice, provides an excellent illustration of how the Supreme Court’s interpretation of a law affects the way in which the law is understood and enforced by the government.

Characteristics of a Good Warrant

Law enforcement officers usually must have a warrant in order to perform a search or seize evidence. But having a warrant is not always enough. For a warrant to be legal, an officer must show probable cause and meet the particularity requirement by listing exactly what and who are to be searched and what evidence the officer expects to find.

Police Informant and Alleged Bomb Plotters This surveillance photo shows a police informant (right) with two bomb plot suspects. Police can often obtain warrants with the help of informants. AP Images.

Showing probable cause

In 1806, the Supreme Court heard its first Fourth Amendment case. This case involved John A. Burford, a Virginia merchant whose temper and behavior were so bad that his neighbors complained to several justices of the peace that they were worried he might commit a crime. In light of their testimony, a court order was issued requiring Burford to pay a bond of $4,000, which he would lose if he committed a crime.

When Burford could not pay the bond (a small fortune at the time) he was arrested and put in jail. When the Supreme Court heard the case, it ordered Burford released from jail. Chief Justice John Marshall (1755–1835) stated that the warrant used to arrest Burford did not comply with any of the Fourth Amendment’s requirements. In particular, he stated that the warrant lacked probable cause to suspect a crime had been committed, because it was based solely on testimony that Burford might commit a crime.

Five years later in Locke v. United States, the Court clearly defined probable cause as “a reasonable ground for belief of guilt” regarding a crime. Without such ground for belief, the court ruled, a warrant was not valid.

Informants and the Aguilar-Spinelli test

Police often use informants in their work. An informant is someone who offers information to the police. Prior to 1964, an officer could obtain a warrant using only an informant’s tip (information). If an informant told the police a house was used to hide stolen goods, for instance, a police officer could use the tip to get a search warrant.

But in Aguilar v. Texas (1964), the Court said an officer must show that an informant is trustworthy and must also explain how the informant came to his or her conclusions. For instance, did the informant witness any wrongdoing or only hear about it secondhand? The judge could then decide whether the informant’s tip justified issuing a warrant.

In Spinelli v. United States (1969), the Court ruled that the conviction of alleged gambler Warren Spinelli must be reversed because an informant’s tip was not sufficiently reliable. For years, the Court applied its so-called Aguilar-Spinelli test to determine whether an informant’s information provided sufficient probable cause. Under the Aguilar-Spinelli test, the government must show a reviewing magistrate (a type of judge) that the informant is reliable and credible and also show the underlying circumstances that caused the informant to come to his conclusions about criminality.

The Supreme Court stated a different opinion in Illinois v. Gates (1983). There the Court stated that a judge should weigh all evidence when considering a warrant, including tips that fail the Aguilar-Spinelli test. This ruling made it easier for police to obtain warrants using informant tips.

Specification in a Warrant

To prevent the kind of general searches common in the colonial era, the Fourth Amendment requires warrants to “particularly describe” the areas to be searched and the type of evidence to be seized. Searches that go beyond the specific scope of a warrant are usually not allowed.

Warrants must also name the people to be searched or arrested, and police are generally not allowed to search people not named on a warrant. In Ybarra v. Illinois (1979), for instance, the Supreme Court ruled that police could not search a patron in a bar who was not named in their warrant. Officers must also use a warrant within a reasonable period of time after it is issued to meet the particularity requirement.

Earls, Lindsey Former Oklahoma high school honor student Lindsey Earls (pictured) sued her school because of its policy of random drug tests. Earls, who tested negative, believed this policy was a violation of her right to privacy. In 2002 the Supreme Court ruled that schools’s interest in ridding their campuses of drugs outweighs an individual’s right to privacy. AP Images.

Shotgun in a shoebox

There are exceptions to the particularity requirement. One of the more common is the plain view rule, which allows officers to seize certain evidence without a warrant if they can see it. For example, an officer with a warrant to search a man at his house for drugs would normally not be allowed to search his visiting grandmother unless she were also named in the warrant. However, if his grandmother were holding drugs in plain sight during the search, the police could seize the evidence without a warrant.

The plain view rule also applies to evidence that may not be out in the open. If police with a warrant to search for drugs at a man’s house found a stolen shotgun hidden under his bed, the officers could seize the gun without a new warrant, because it was reasonable for them to look for drugs under the bed. By contrast, if police had a warrant to search for a shotgun and uncovered stolen gems hidden in a shoebox, they could not use the gems as evidence, because there was no reason to search the shoebox for a shotgun.

Officer in jeopardy.

The court has also ruled that officers may search people for weapons, even if they are not named in a warrant, when the safety of officers or other people in the area may be jeopardized. If officers have a warrant to arrest a particular gang member, for instance, they may search other gang members in the area for weapons while making the arrest.

Necessity for Warrants

The Fourth Amendment establishes requirements for obtaining legal warrants and prohibits unreasonable searches. Nowhere, however, does the amendment say that all searches must begin with a warrant. The “plain view rule” and limited weapon searches (sometimes called “stop and frisk”) allow officers to go beyond the scope of a warrant in certain situations. But officers may also conduct certain kinds of searches with no warrant at all. The Supreme Court has dealt repeatedly with the issue of when and if a search requires a warrant.

Postal Worker Sorting Mail A postal worker sorts mail. The Supreme Court has ruled that mail is not subject to warrantless searches. AP Images.

Extending the bounds of the Fourth Amendment

In the 1877 case of Ex Parte Jackson, postal inspectors argued that the mail was subject to warrantless searches. But the Supreme Court ruled that one’s mail is protected against unreasonable search and seizure, just as private papers are in one’s home. As long as a person’s mail is held by the post office, it can only be opened by an official who has obtained a legal warrant. Otherwise, it must remain sealed and secure.

The case of the “searchless” search.

In Boyd v. New York (1886), the import company E. A. Boyd & Sons, was accused of not paying duties (government import fees) on a quantity of imported plate glass. An 1874 federal law gave the government the power to force Boyd & Sons to produce an invoice (receipt) for the glass it had imported. Using the invoice as evidence, the government proved that the company had not paid the duty.

The company protested that the law violated the Fourth Amendment and the Fifth Amendment, which protects defendants from being forced to incriminate themselves (see chapter six). The government argued that the Fourth Amendment applied only to physical searches of private property, and because no such search had been made, no violation had occurred.

The Supreme Court disagreed. Justice Joseph P. Bradley (1813–1892) observed that by forcing defendants to hand over the same type of evidence that might be found in an actual search and seizure without obtaining a warrant, the law violated the Fourth Amendment. Because the law that helped convict Boyd & Sons was deemed unconstitutional, the Court threw out the conviction, despite the fact that evidence showed the company had broken the law.

Reasonable expectation of privacy.

In 1967, the Supreme Court established a general rule for determining when a search requires a warrant. Federal agents had used electronic listening devices (without a warrant) to eavesdrop on Charles Katz as he talked in a public phone booth. The police later used recordings of these calls to prove Katz was involved in illegal gambling activities.

Traffic Stop A police officer approaches a vehicle during a traffic stop. Officers are allowed to seach a person’s car without a warrant if they suspect the driver might be carrying something illegal. AP Images.

The Supreme Court, however, found that the government eavesdropping met the definition of a search and seizure under the Fourth Amendment, because the actions “violated the privacy upon which [Katz] justifiably relied while using the telephone booth.” The case established that if a defendant has a “reasonable expectation of privacy” when a search is performed, a warrant is required. In his concurring opinion in Katz, Justice John Marshall Harlan identified a two-part test for determining whether a defendant had a “reasonable expectation of privacy.” Those two parts are (1) whether the defendant exhibited a subjective expectation of privacy; and (2) whether society recognizes the expectation of privacy as objectively reasonable.

Search and seizure without a warrant

Although the reasonable expectation of privacy standard was used to expand Katz’s protection from searches outside his home, the same general rule was subsequently used to justify a variety of warrantless searches.

Search issues regarding cars.

As early 1925 (Carroll v. United States) the Court allowed warrantless searches of automobiles if the officer had probable cause to believe the vehicle contained illegal goods, because a vehicle might slip away before an officer could obtain a warrant. But in Cardwell v. Lewis (1974), the Court used the Katz standard to further justify vehicle searches stating that “One has a lesser expectation of privacy in a motor vehicle because its function is transportation and it seldom serves as one’s residence.”

Though this ruling allows for many vehicle searches, the Supreme Court has stated that full vehicle searches are not allowed when a driver is stopped for a traffic violation and the officer has no probable cause to suspect other criminal conduct (Knowles v. Iowa [1998]).

Privacy outdoors.

The expectation of privacy standard has also been used to allow searches of open fields without a warrant, except in the area “immediately around the home.” However, even there, the Court has ruled that a person does not have a reasonable expectation of privacy from aerial surveillance. In light of these rulings, searches conducted by police helicopters or airplanes rarely require a warrant, and aerial searches of private property for marijuana fields and other contraband became routine in the twentieth century.

The stop and frisk.

The case of Terry v. Ohio (1968) created another form of warrantless search. Prior to this case, police needed to have probable cause before making an arrest. But in Terry, the Court ruled that a police officer need only reach two conclusions to justify a warrantless stop and frisk: first, that criminal activity may be going on and second, that the suspect may be armed and dangerous.

In such cases, police can conduct a “carefully limited search” of the suspect’s outer clothing for weapons for the safety of officers and others in the area. Some people argue that the decision to allow “suspicion-based” searches without a warrant considerably weakens the probable cause requirement for searches.

An officer in “hot pursuit” of a suspected felon (someone who has just committed a crime) may conduct a warrantless search for the fleeing suspect. And in cases where evidence may readily disappear, as in blood samples from drunken drivers, an officer may seize that evidence without a warrant.

What to Do with “Bad” Evidence

Man Blowing into Breathalizer A man blows into a breathalyzer to test for alcohol. Police are allowed to administer sobriety tests to drivers without a warrant. Justin Sullivan/Getty Images.

Despite such exceptions, most searches do require a warrant, and most warrants must meet the particularity requirement and show probable cause. But what happens to evidence when the police break these rules? The Fourth Amendment is silent on the subject, leaving it to the Supreme Court to decide just what can be done with the evidence of unconstitutional searches. Those rulings have not always been consistent.

Why waste evidence?

In Boyd v. United States (see above), the Supreme Court leaned toward excluding illegally obtained evidence. But in Adams v. New York (1904), the Court ruled that evidence seized by the government that was not listed on a search warrant could be used against the defendants. The Court stated that English courts and nearly all U.S. courts had historically refused to throw out evidence just because it was obtained illegally. The Court reasoned that a criminal should not go free because the police made a mistake.

The exclusionary rule

In the case of Weeks v. United States (1914), the Supreme Court changed its mind about illegally obtained evidence. Officers had searched the home of Fremont Weeks without a warrant and seized envelopes that linked Weeks to illegal gambling activities.

Weeks claimed that the search and seizure violated his Fourth and Fifth Amendment rights and that his personal property should be returned to him. The government lawyers assumed that the Adams v. New York decision allowed them to use the evidence regardless of how it was obtained.

But the Supreme Court agreed that Weeks’s property (which just happened to be the evidence against him) should have been returned to him because it had been seized illegally. Additionally, the Court reasoned, if his property was returned, it could not be used to convict him.

“If letters and private documents can (be seized illegally) and held and used in evidence,” wrote Justice William Rufus Day (1849–1923), “the protection of the Fourth Amendment might as well be stricken from the Constitution.” The idea that illegally obtained evidence should not be used against a defendant, even when it proves the defendant’s guilt, became known as the exclusionary rule, and as of the early 2000s, this rule stands as one of the Court’s most important and controversial interpretations of law.

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Weighing society’s interests

The Supreme Court has established particular situations where a warrantless search may be legal, such as when evidence is in plain view or when an officer is in hot pursuit of a felon (criminal). But the Court has also determined that there are certain people and places where the community’s interests outweigh an individual’s Fourth Amendment rights.

Railroad employees and customs officers, for instance, can be searched and tested for drugs without a warrant because their jobs involve public safety. Along U.S. borders, customs officials have the power to search anyone without a warrant, probable cause, or suspicion because the nation has an interest in protecting its boundaries. Prisons are another place where people have no Fourth Amendment protections.

Many lower courts have ruled that locker searches, drug-sniffing dogs, and the search of student vehicles on school property are legal and that school officials may conduct such searches without warrants or probable cause. Yet, as of 2007, the Supreme Court has heard very few cases on the subject of searches on public school grounds. In a 1985 decision, New Jersey v. T.L.O., the Court recognized that although public school students enjoy certain Fourth Amendment protections, neither probable cause nor the warrant requirement is necessary because school officials are government agents when they carry out searches. As a result, they may conduct a search based on a general standard of reasonableness. This reasonableness standard requires that the search be justified at its inception and that it be reasonably related in scope to the initial inquiry.

Man Blowing into Breathalizer A policeman and his drug-sniffing dog search high school lockers. AP Images.

One concept the courts have pointed to in making these rulings is that school officials behave in locus parentis—in the place of parents. In other words, while students are at school, teachers and administrators have the same rights and responsibilities as a child’s parents. Other courts have pointed to the fact that lockers, desks, and other property that belong to the schools never become the property of the students and, therefore, is never protected from a school search. However, the Supreme Court has never specifically ruled on this issue.

In Vernonia School District v. Acton (1995), the Court ruled 6–3 that random drug tests of student athletes were legal. In the opinion, the Court stated that students could choose to avoid the searches by choosing not to play sports. The Court also used the expectation of privacy standard, stating that student athletes have a decreased expectation of privacy because they play sports. In Board of Education v. Earls (2002), the Court ruled 5–4 that a public school district in Oklahoma could conduct drug tests on any student participating in any extracurricular activity.

One area where both the Supreme Court and the lower courts have seemed to draw the line is the strip searching of students. Both courts have ruled that even partial bodily searches of students are an invasion of privacy. In a federal appeals court case involving the routine use of drug-sniffing dogs and strip searches in schools, the Court stated that a strip search of a young girl was an “invasion of constitutional rights of some magnitude.”

Excluding fruits of a poisonous tree

Other cases have expanded the scope of the exclusionary rule. In Silverthorne Lumber Co. v. United States (1920), police officers made copies of illegally seized books and papers before returning the evidence to the defendants. The government then used the copies to convict the company of wrongdoing. The government attorneys argued that the Fourth Amendment only required the return of illegally seized evidence.

But the Supreme Court disagreed. Justice Oliver Wendell Holmes (1841–1935) argued that evidence gained in violation of the Fourth Amendment should not be used in any way. This assertion, that any evidence obtained as result of illegally obtained evidence should not be used, is known as excluding the “fruit of the poisonous tree.”

Hot evidence on a silver platter

In seeming contradiction to this ruling was the so-called silver platter doctrine. The limits of government found in the Bill of Rights initially only applied to the federal government, not the individual state governments. The Supreme Court began to extend the reach of the Bill of Rights to include state government in the 1920s (see chapter fourteen), but the process took several decades to complete. Therefore, until the 1960s, different rules applied at the state and federal levels, which could lead to complicated situations when local and federal law enforcement agencies cooperated on a case.

In Byars v. United States (1927), the Supreme Court ruled that federal officials could use evidence that had been seized illegally by state police as long as state officers had not conducted the search on behalf of the federal government and no federal officers participated in the search. In other words, as long as the state government served the evidence up on “a silver platter” to the federal officials, the evidence could be used. In Elkins v. United States (1960), the Court did away with the silver platter doctrine, and a year later the states were also prohibited from using illegally obtained evidence.

Making States Play by the Rules

The Supreme Court initially implemented the Fourth Amendment in the states without compelling the local governments to abide by the exclusionary rule. In the case of Wolf v. Colorado (1949), a local sheriff entered the office of Dr. Julius Wolf with a warrant and seized documents that were later used to convict Wolf of performing illegal abortions. Wolf appealed to the Supreme Court, and the Court ruled that the Fourth Amendment did apply to the states (see chapter fourteen).

However, the Court ruled that the states did not have to exclude illegally obtained evidence, and Wolf’s conviction was not overturned. The Court stated that the exclusionary rule was only one way to deter illegal searches, and states were free to choose others, such as allowing citizens to sue officials who performed illegal searches. Disagreeing with the ruling. Justice Frank Murphy (1890–1949) wrote: “The conclusion is inescapable that but one remedy exists to deter violations of the search and seizure clause.” Namely, the exclusionary rule.

Applying the rules

Because most criminal cases in the United States are tried at the state level where the exclusionary rule was not enforced, the rule had very little effect on criminal law through much of the twentieth century.

This changed with the 1961 case of Mapp v. Ohio. After being tipped off that Dollree Mapp might be in possession of bomb-making materials, police officers (claiming to have a warrant) broke into Mapp’s home and ransacked her possessions. The officers claimed to have found obscene materials during their search, and Mapp was later convicted of violating a state obscenity law based on this evidence. However, no warrant was ever produced at the trial.

When the Supreme Court heard the case, the state of Ohio pointed to the decision in Wolf, arguing that even if the search had been made without a warrant, nothing prevented the state from using the illegally obtained evidence. The Court, however, took this opportunity to overturn the Wolf ruling and extended the exclusionary rule to the states.

Few developments in constitutional law have changed the landscape of law enforcement so much or have been as controversial. Opponents denied that there was any constitutional basis for the rule and argued that it punished officers for making mistakes while letting criminals go free.

Proponents of the exclusionary rule believed it was the only way to give the Fourth Amendment effectiveness and prevent abuses of police power. Justice Tom Clark (1899–1977) wrote, “We can no longer permit [the Fourth Amendment] to be revocable at the whim of any police officer.” He argued that although the exclusionary rule allowed some criminals to go free, the tradeoff was worthwhile because “nothing can destroy a government more quickly than its failure to observe its own laws.”

Allowing for Honest Mistakes

In the 1984 case of United States v. Leon, the Court staked out some middle ground between the opposing views of the exclusionary rule. A magistrate had issued a defective search warrant in a drug case, and because of the mistake, drug evidence seized in a raid was excluded from a lower court trial. However, the Supreme Court reversed that decision, ruling that evidence obtained under a warrant that is later ruled to be invalid could be used if the law enforcement officer acted reasonably. This rule is called the Leon good-faith exception.

In this ruling, the Court said that criminals should not benefit from honest mistakes. Justice Byron R. White (1917–) wrote that the exclusionary rule was created “to deter police misconduct rather than to punish the errors of judges and magistrates.”

The Court broadened the so-called good faith exception in Arizona v. Evans (1995). A court employee had mistakenly listed Isaac Evans as the subject of a misdemeanor arrest warrant. A police officer who stopped Evans for a traffic violation searched him under the authority of that warrant and found marijuana in his possession. At the trial, Evans succeeded in having the marijuana evidence suppressed.

But the Supreme Court voted to allow the evidence, arguing that evidence seized as a result of a clerical error is admissible at trial, since the exclusionary rule’s purpose was to deter intentional police abuses. Critics of the Evans and Leon rulings, however, have argued that the good faith exception gives police the option to abuse their search and seizure powers.

Bags of Marijuana Bags of marijuana seized by police. In Evans v. Arizona the Supreme Court allowed the marijuana evidence found during a traffic violation search. AP Images.

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Police, Thieves, and the Use of Stolen Evidence

The Fourth Amendment applies specifically to the actions of law enforcement officers and court officials, but it does not protect against searches by people other than the police. In fact, the Court has ruled that evidence gained by illegal methods is admissible (useable) in court, as long as the police were not involved in getting it.

In 1918, as the United States was engaged in World War I (a conflict largely between European nations that lasted from 1914 to 1918) the U.S. Intelligence Department became convinced that Felix Gouled was involved in a conspiracy to defraud the government. The government enlisted the help of an army private who knew Gouled to help gather evidence against him. The soldier visited Gouled at his office on a “social call” and while he was there, he took some of his host’s papers and turned them over to the federal agents.

The government used evidence from the stolen papers to show probable cause for a search warrant and used the evidence gathered with the warrant to arrest Gouled and charge him with conspiracy. In 1921, Gouled’s case came before the Supreme Court, and the Court ruled that none of the evidence, neither that stolen by the soldier nor any of the evidence found during the later searches, could be used.

At the time the Supreme Court did not allow the seizure of papers that were not in themselves illegal. In order to be seized, evidence had to be contraband (illegal goods) such as drugs or stolen property. However, the Court also ruled that because a government law enforcement agency had urged the soldier to steal the evidence, the soldier was essentially conducting a government search without a warrant; therefore, the evidence was excluded.

That same year the Court heard Burdeau v. McDowell (1921). In that case, a man stole evidence without any governmental authority and later turned it over to law enforcement officials. The Supreme Court ruled that because the Fourth Amendment, and therefore the exclusionary rule, only apply to government agents, evidence that is illegally obtained by a person with no connections to law enforcement can be used in court.

In other words, a police officer cannot enter someone’s home and take useable evidence without a warrant, but a burglar probably can.

The Elastic Shield

The protections provided by the Fourth Amendment, though simply stated, have not proved as simple to interpret. Since the first Fourth Amendment case in 1804, the Supreme Court has limited the government’s search and seizure power (in cases such as Weeks, Katz, and Mapp) and expanded it (in cases such as Adams and Terry.

Like other amendments, the Fourth Amendment has been interpreted and reinterpreted, often in response to the changing values and conditions of a given time. Even if its exact dimensions have been stretched and narrowed, the Fourth Amendment still provides Americans with an exceptional shield against intrusive police searches and unjustifiable seizures of private property. For example, the Supreme Court in an opinion in Kyllo v. United States (2001) by conservative justice Antonin Scalia, ruled that the use outside a person’s home of a thermal imager (to detect hotspots for evidence of marijuana growth) constituted a search within the meaning of the Fourth Amendment. Scalia reasoned: “Where, as here, the Government uses a device that is not in general public use, to explore details of the home that would previously have been unknowable without physical intrusion, the surveillance is a ‘search’ and is presumptively unreasonable without a warrant.”

The Fourth Amendment remains vitally important in preserving individual privacy from governmental intrusion. However, the War on Terror after the September 11, 2001, terrorist attacks on the United States was anticipated by some to test the nation’s commitment to Fourth Amendment principles in the name of national security. Some believe that the law passed forty-five days after September 11—the Providing Appropriate Tools Required to Intercept and Obstruct Terrorism Act (PATRIOT Act)—may infringe on fundamental Fourth Amendment principles. Others counter that the War on Terror requires a greater sacrifice on the part of individuals for the common good and national security.


For More Information


Fleetwood, Alice. Privacy Rights: Cases Lost and Causes Won before the Supreme Court. Lanham, MD: Rowman & Littlefield, 2006.

Gonzales, Doreen. A Look at the Fourth Amendment : Against Unreasonable Searches and Seizures. Berkeley Heights, NJ : Books, 2007.

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Source Citation

Source Citation   

Gale Document Number: GALE|CX2639900004