suppression of evidence

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Suppression of evidence is a pretrial proceeding to prevent evidence from being shown at trial, which could be lawful or unlawful. 

Lawful suppression of evidence means the judge rejects the use of the evidence in the court because they think that the evidence may be inadmissible due to a violation of the Constitution or other statutes that permit the evidence to be excluded. For instance, the evidence is obtained in violation of the Constitutional rights of a defendant. The suppression request is usually raised by a pretrial motion made by a criminal defendant. The admissibility of evidence is a preliminary question that can only be resolved by the judge. Once the judge believes the evidence should be suppressed, it will not go to the trial. The jury, which only assesses the credibility of evidence, usually has nothing to do with the suppression of the evidence.

Unlike lawful suppression of evidence proposed by a defendant, an unlawful suppression of evidence is made by a prosecutor who improperly or intentionally hides or withholds evidence. Since the Brady Rule requires prosecutors to disclose material evidence possessed by the government, if prosecutors fail to disclose it, the evidence then cannot be used at trial. See Brady v. Maryland, 373 U.S. 83 (1963).

Grounds for Suppression

The Fourth Amendment: Exclusionary Rule

An unreasonable search or seizure is is a violation of the Fourth Amendment. The exclusionary rule is the remedy to an unreasonable search and seizure, which suppresses any evidence seized via such a search; see Mapp v. Ohio, 347 U.S. 643 (1961). This remedy only applies to criminal trials. Even though the defendant can get evidence excluded, they cannot get a remedy against the government officials who performed unreasonable search or seizure, for the officer has qualified immunity. This rule is to protect government employees executing their working assignments from being personally sued by the defendant. 

For instance, evidence seized pursuant to an unlawful arrest may be suppressed at trial, while a voluntary confession made after that arrest will not automatically be suppressed. But if the confession is too closely tied to the illegal arrest which may not be truly voluntary, it may be suppressed; see Wong Sun v. U.S., 371 U.S. 471 (1963).

There are some exceptions to the exclusionary rule that evidence obtained will not be suppressed; they are good faith exceptions, independent source doctrine, inevitable discovery doctrine, attenuation doctrine, and evidence admissible for impeachment. 

The Fifth Amendment: Miranda Warning

Any incriminating statement (e.g., a confession) of a suspect obtained as the result of custodial interrogation (question asked by known police or other known law-enforcement officers after being taken into custody) is inadmissible and should be suppressed in the subsequent trial. However, if the suspect was informed of their Miranda rights, which gives procedural protection to privilege against self-incrimination, but they still made that statement, the statement is admissible, as their rights are waived. If the suspect made two statements, one before the Miranda warning and the other after it, the second confession is admissible unless “the circumstances indicate that the substance of Miranda has been drained away” see Oregon v. Elstad, 470 U.S. 298 (1985). The suppression of incriminating statements is not automatic.

Fruit of the poisonous tree confessions include any physical derivative evidence which is obtained as a result of a non-Mirandized confession; they are admissible if the confession is not coerced: see United States v. Patane, 542 U.S. 630 (2004).

The Sixth Amendment: Assistance of Counsel 

The Sixth Amendment guarantees a criminal defendant “the right to effective assistance of counsel” unless the defendant knowingly and voluntarily waives that right, it is automatically initiated.   

The Sixth Amendment also guarantees a criminal defendant “the right to a public trial.” The right to a public trial extends to suppression hearings (e.g., a motion that a defendant moves to suppress an identification). 

If the counsel fails to submit a motion to suppress evidence, they might be ineffective and incompetent, and the conviction may get overturned.


Since a pretrial motion to suppress is a mix of the question of fact and law; once appealed, the question of law is reviewed de novo by the judge while the question of fact is reviewed for clear error

[Last updated in June of 2022 by the Wex Definitions Team