Mapp v. Ohio Case Summary: What You Need to Know

The Fourth Amendment provides important protections against unreasonable search and seizure. In Mapp v. Ohio, the Supreme Court held that evidence gathered in violation of the Fourth Amendment cannot be used in a criminal trial. 

The 1950s and '60s were an integral time for civil rights. The developments, both legal and social, that came out of this time have shaped the U.S. legal system for decades. And in 1961, a crucial case ensured that police must follow the Constitution when gathering evidence.

In a 6-3 decision, the Supreme Court in Mapp v. Ohio ruled that evidence obtained in violation of the Fourth Amendment is inadmissible in state court.

Use the links below to skip to different sections:

Background of the Case

The case began in Cleveland, Ohio, in 1957 when police demanded entry into 34-year-old Dollree Mapp's home. Although they believed Mapp was hiding a suspected bomber, the police had no search warrant. After calling her lawyer for advice on what to do, Mapp refused to let them in.

Thirteen hours later, Cleveland police returned and forced their way inside Mapp's house. They gave Mapp a piece of paper they claimed was a search warrant, but Mapp did not have an opportunity to view it before police entered her home.

They did not find the suspect but did find a trunk of pornographic books and photos in Mapp's basement. Months later, she refused to testify against mobster Shondor Birns - and found herself facing charges of possession of pornography based on what police found in her home.

At trial, no search warrant was produced - and the police officers gave no reason for it to be missing. Mapp filed a lawsuit, arguing that police had violated her rights under both the First and Fourth Amendments.

Mapp's First Amendment argument focused on freedom of expression. She argued that this freedom included a right to possess "obscene materials." The Fourth Amendment issue surrounded the protection against unreasonable searches and seizures.

When her case reached the Supreme Court, the justices decided the First Amendment issue was irrelevant, proceeding with only the Fourth Amendment issues.

Protection from Unreasonable Searches & Seizures

The Fourth Amendment guarantees the right to be free from "unreasonable searches and seizures." Seen as a fundamental right, this Amendment grew directly from what colonists experienced under British rule. Using what were known as "writs of assistance," British officers could enter anyone's home to search for evidence of a crime.

By adding the Fourth Amendment to the United States Constitution, the Framers created enhanced protection from such practices. Specifically, it requires that someone's home, belongings, and their person cannot be searched without a warrant or probable cause.

The Supreme Court's Decision in Mapp v. Ohio

In 1961, Mapp's case reached the Supreme Court, then led by Chief Justice Earl Warren. The majority opinion for the 6-3 decision was written by Justice Tom C. Clark. The six justices in the majority declared that any evidence obtained in a search conducted in violation of the 4th Amendment cannot be admitted in state court.

This decision overturned Wolf v. Colorado, a 1949 case which held that the 4th Amendment did not forbid the use of illegally obtained evidence in state court. In Wolf, the Supreme Court held that it was up to the state courts to adopt the exclusionary rule. And if they hadn't, they must already have some other mechanism for deterring police misconduct. So, until the court took up the issue again in Mapp, state courts could admit evidence obtained illegally.

In Mapp, the Supreme Court found there was no reason that states should not be held to the same standard as the federal government:

"This Court has not hesitated to enforce as strictly against the States as it does against the Federal government the rights of free speech and of a free press, the rights to notice and to a fair, public trial, including, as it does, the right not to be convicted by use of a coerced confession... Why should not that same rule apply to what is tantamount to coerced testimony by way of unconstitutional seizure of goods, papers, effects, documents, etc.?"

The majority opinion relied on the legal doctrine of "selective incorporation." Selective incorporation is derived from the Fourteenth Amendment's due process clause, which bans states from making laws that infringe on the rights of American citizens.

Using selective incorporation, the court found that state courts were subject to what is known as the "exclusionary rule."

What Is the Exclusionary Rule?

In the broadest sense, the "exclusionary rule" prohibits the government from using evidence gathered in violation of the Constitution. Created by the Supreme Court in 1914, the exclusionary rule made Fourth Amendment protections more effective for criminal defendants.

Intended to deter police misconduct, the rule allows courts to exclude evidence - even if it proves guilt - if law enforcement obtained it without a search warrant or some other constitutional justification.

For the first 50 years the exclusionary rule was in play, it was only applied in federal proceedings. However, the Supreme Court's decision in Mapp v. Ohio extended it to state courts.

Fruit of the Poisonous Tree

The exclusionary rule can also extend to chains of evidence, through a doctrine known as "fruit of the poisonous tree." This describes the idea that evidence collected based on other, illegally obtained evidence is also not admissible.

For example:

Police find significant physical evidence based on information they obtain by interrogating a suspect. But, it turns out the arrest or interrogation was carried out illegally. In that case, the intel from the questioning and the physical evidence could be inadmissible at trial. Because without the unlawfully obtained info, they wouldn't have found the physical evidence.

Today, the exclusionary rule and the "fruit of the poisonous tree" doctrine are seen as fundamental principles of criminal law.

Dissenting Opinions

Justice John M. Harlan disagreed with the majority when they opted to dismiss Mapp's First Amendment arguments. Instead, he argued, they should have focused solely on these issues. Because Mapp was convicted under an Ohio statute that criminalized the possession of pornography, he explained, the real problem was whether that law was "consistent with the rights of free thought and expression assured by state action by the 14th Amendment."

Justice Harlan also believed that applying the exclusionary rule to the states violated the principles of stare decisis and judicial restraint.

Stare decisis refers to the credit the Supreme Court gives to its own decisions. It's because of this doctrine that the court rarely overturns its own opinions. Justice Harlan believed that because the court had addressed the exclusionary rule issue in Wolf, the majority was wrong to change the rule in Mapp.

Judicial restraint is a concept that judges should consciously limit their own power by resolving cases in the narrowest way possible. In his dissent, Justice Harlan accused the majority of "reaching out" to decide the case on Fourth Amendment grounds when they should have limited themselves to the First Amendment issue.

Weeks v. United States - In this 1914 case, the Supreme Court established the exclusionary rule by finding the federal government could not use illegally obtained evidence in federal court to obtain a conviction. The court in Mapp extended this ruling to state court proceedings.

Silverthorne Lumber Co. v. United States- The Supreme Court established the "fruit of the poisonous tree" doctrine in 1920 with Silverthorne Lumber Co. Police had illegally seized tax books from Silverthorne Lumber and made copies of the records inside. The court found the copies made were inadmissible because they were "tainted" by the illegality of the initial search.

Nix v. Williams- In 1984, the Supreme Court placed a limit on the Mapp decision and created the "inevitable discovery rule." Under inevitable discovery, a piece of evidence that would have eventually been discovered through legal means is admissible.

United States v. Leon - Also decided in 1984, U.S. v. Leon established the "good faith" exception to the exclusionary rule. Essentially, if a police officer believes that their search is legal, the evidence can be admitted in court. This rule requires judges to determine whether an officer acted in "good faith," and often comes up when there are issues with a search warrant that an officer does not know about.

Read the Supreme Court's full decision from Mapp v. Ohio on FindLaw's Cases & Codes.

Was this helpful?


Learn about the nation's highest court and its most famous decisions.

Read more >