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The Exclusionary Rule: What Is It?


The Exclusionary Rule is a legal principle that prohibits the use of evidence obtained in violation of the Fourth Amendment to the United States Constitution. The rule applies to both federal and state courts and has been interpreted to apply to all types of evidence, including confessions, eyewitness identifications, and physical evidence. The purpose of the exclusionary rule is to deter law enforcement from violating constitutional rights by ensuring that any illegally-obtained evidence will not be admitted at trial. Despite its purpose, however, the exclusionary rule has been criticized as being ineffective and actually harming criminal investigations.

What is a Miranda Warning?

The Miranda Warning is a set of standards that were established in the 1966 Supreme Court case, Miranda v. Arizona. The purpose of the Miranda Warning is to ensure that criminal suspects are aware of their constitutional rights before they are interrogated by law enforcement. The specific wording of the Miranda Warning may vary depending on the jurisdiction, but it typically includes information about the right to remain silent and the right to an attorney.

exclusionary rule

What Is Exclusionary Rule?

The exclusionary rule is a legal principle that holds that evidence obtained through illegal or unconstitutional means cannot be used in criminal prosecutions. The rationale behind the rule is to deter law enforcement from engaging in illegal or unconstitutional activity, and to protect the constitutional rights of defendants. The exclusionary rule is not a blanket prohibition on the use of all illegally-obtained evidence; rather, it is a tool for courts to use in weighing the probative value of the evidence against its potential to prejudice defendants.

The exclusionary rule is derived from the Fourth Amendment’s Bill of Rights and is intended to safeguard people against unlawful searches and seizures. The exclusionary rule aims to provide a remedy, as well as a disincentive, for criminal prosecution by prosecutors and cops who gather evidence illegally in violation of the Fifth Amendment’s protection against self-incrimination. The exclusionary rule safeguards against breaches of the Sixth Amendment, which guarantees access to legal counsel.

Scope and Limitations of the Exclusionary Rule:

The scope of the exclusionary rule varies from jurisdiction to jurisdiction, but it typically applies to all law enforcement agencies, including police, prosecutors, and even courts. In some jurisdictions, the rule may also apply to private individuals and entities. 

In a civil action, grand jury proceeding, or parole revocation hearing, the exclusionary rule does not apply. Whether the actions were unlawful for exclusionary rule reasons is determined by the legislation in force at the time of the police action rather than at the time of the attempt to introduce evidence.

The fruit of the poison tree doctrine is a legal principle that holds that evidence obtained by illegal means, such as through torture, is inadmissible in court. The rationale behind the doctrine is that it would be unfair to allow the government to benefit from its own wrongdoing.

When a defendant is arrested illegally, the government may not use fingerprints taken while the individual was in jail as evidence. Because cops would not have acquired the prints without an unlawful arrest, they are “fruit of the poisonous tree.”

At any rate, the “fruit of the poisonous tree” principle does not apply to interrogations carried out without a Miranda warning. Although a confession procured in violation of Miranda is inadmissible, evidence acquired as a result of what was stated during the interrogation is admissible. For example, if the identity of a witness is obtained through a confession that breaches Miranda, the government may still use the witness’s testimony at trial.

Limitations on the exclusionary rule have included the following:

Private search doctrine: The defendant’s property and assets are not admissible if they were acquired illegally by a third party. The Fifth Amendment is intended to safeguard personal freedoms, with the Fourth Amendment applying particularly to law enforcement agents.

Standing requirement: The illegal search of a third party’s privacy rights cannot be undone, regardless of when it occurred. The exclusionary rule does not apply to the privacy rights of a third person. There is, however, an exception to this standing requirement under the jus tertii standing exception.

Cross-examination: Unlawfully obtained evidence may be used on cross-examination to challenge the defendant’s credibility, at least where it is necessary to avoid gamesmanship. For example, if the defendant expressly states that he has no narcotics ties, he cannot use the exclusionary rule as a defense against attacks on his trustworthiness. However, the government may not attempt to “smuggle in” excluded evidence during cross-examination by asking wide inquiries.

Inevitable discovery doctrine: In Nix v. Williams, the court ruled that if the evidence found as a result of the illegal search would almost certainly have been discovered eventually even without said search, it may be presented in court.

Good faith exception: Under the good-faith exception, evidence obtained as a result of a defective search warrant may still be used if police officers acting in good faith (bona fides) rely upon it.

Independent Source Doctrine: If police acquire evidence illegally, but also through a legal approach, it is admissible.

Knock-and-Announce Exception: Police may search your home without a warrant if they obtain evidence in violation of the regulation to bang and announce themselves before doing so.

Attenuation: If the temporal connection between the illicit activity and the evidence is disrupted, the evidence may still be admissible if other factors have altered. The following are some examples:

  • If a person is illegally detained but returns voluntarily to the police station several days later and gives a statement, the statement may be admitted.
  • If a defendant was illegally stopped, and yet an outstanding arrest warrant is subsequently discovered, the evidence obtained during the stop may be admissible.
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