The Exclusionary Rule

Fundamentals of Procedural Law by Adam J. McKee

The Exclusionary Rule is a critical component of American criminal law that safeguards against unconstitutional police conduct. This legal principle holds that evidence obtained in violation of a defendant’s constitutional rights cannot be used in a criminal trial. The rule is intended to deter law enforcement from engaging in illegal conduct by denying them the potential benefits of such behavior.

The Foundation: Weeks v. United States

The foundation for the Exclusionary Rule lies in the landmark Supreme Court case, Weeks v. United States (1914). In this case, the Court held that evidence seized during an illegal search and seizure was inadmissible in a federal court trial. The defendant’s constitutional right against unreasonable searches and seizures under the Fourth Amendment had been violated, and the Court decided that the use of unlawfully obtained evidence would erode constitutional protections.

Purpose and Logic of the Rule

The purpose and logic of the Exclusionary Rule are deeply rooted in respect for constitutional rights and the rule of law. By excluding evidence obtained through unconstitutional methods, the rule seeks to discourage police misconduct and uphold the integrity of the criminal justice system. It sends a clear message: The ends (securing convictions) do not justify the means (violating constitutional rights).

Application and Evolution: Mapp v. Ohio

While Weeks v. United States established the Exclusionary Rule in federal courts, it was the decision in Mapp v. Ohio (1961) that extended its application to the states. This was a significant development, as the vast majority of criminal prosecutions occur in state courts. The Mapp case underscored that constitutional rights apply uniformly across all levels of the justice system.

In Mapp v. Ohio (1961), the Supreme Court provided a comprehensive rationale for the Exclusionary Rule, particularly in its application to the states. The Court’s legal logic revolved around the necessity of effective deterrence against Fourth Amendment violations and the preservation of judicial integrity.

Dollree Mapp’s home had been searched without a warrant, leading to her arrest based on material found during this illegal search. At the heart of the Court’s ruling was a determination that the protections of the Fourth Amendment were meaningless unless there was a method to enforce them.

The Court reasoned that allowing state courts to admit evidence obtained in violation of the Constitution would, in essence, endorse law enforcement’s disregard for the Fourth Amendment. Thus, the Court held that evidence seized illegally could not be used in state courts, effectively extending the Exclusionary Rule to all levels of the American legal system.

The majority opinion underscored the need for an effective deterrent against reckless invasions of privacy by law enforcement officials. This need was deemed paramount, even if it sometimes meant that evidence of guilt would be excluded, and guilty defendants might go free as a result. The Court believed that the potential exclusion of evidence would encourage law enforcement to conduct searches and seizures lawfully.

In Mapp v. Ohio, the Supreme Court used the Due Process Clause of the Fourteenth Amendment as a conduit for incorporating the Fourth Amendment protections against the states. This incorporation doctrine was critical to the Court’s decision, as it ensured that the fundamental safeguards of the Fourth Amendment would be upheld in state, as well as federal, courts. Thus, Mapp formed the bedrock for the application of the Exclusionary Rule in state courts and its fundamental role in U.S. criminal procedure.

Controversies and Critiques

While the Exclusionary Rule is a vital instrument for protecting constitutional rights, it has also faced criticism. Detractors argue that it allows guilty persons to escape conviction due to procedural errors, putting societal safety at risk. The Court has grappled with these criticisms in various cases, carving out exceptions to the rule where the societal cost of exclusion outweighs the deterrence benefits.

The dissent in Mapp v. Ohio contended that the extension of the Exclusionary Rule to states was unnecessary and even harmful. Justice Harlan, writing the dissent, argued that each state should have the autonomy to devise its own rules on the admissibility of evidence. He warned that this rule would lead to the acquittal of guilty defendants, compromising public safety. Moreover, he proposed alternative remedies for illegal searches, such as civil damages or disciplinary action against offending police officers. He believed these could provide sufficient deterrence against Fourth Amendment violations without unduly impacting the state’s ability to prosecute crime.

Despite these debates, the Exclusionary Rule remains a cornerstone of American criminal procedure, emblematic of the balance between societal interests in crime control and individual rights against governmental overreach.


Modification History

File Created:  08/08/2018

Last Modified:  07/24/2023

[ Back | Content | Next]

This work is licensed under an Open Educational Resource-Quality Master Source (OER-QMS) License.

Open Education Resource--Quality Master Source License


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.