Defense counsel files a written motion identifying the specific evidence to be suppressed, the constitutional violation alleged (4th, 5th, or 6th Amendment), and supporting legal authority.
The prosecution files an opposition brief arguing the evidence was lawfully obtained, often asserting an exception to the warrant requirement or that no constitutional right was violated.
The court holds a suppression hearing where the government bears the burden of proving the evidence was obtained constitutionally. Officers and witnesses may testify.
Defense counsel cross-examines government witnesses, probing inconsistencies in testimony and challenging the reasonableness of the officers' actions.
Both sides present closing arguments applying the facts established at the hearing to the applicable legal standards (reasonable suspicion, probable cause, voluntariness).
The judge issues findings of fact and conclusions of law. If granted, the evidence is excluded from trial and the "fruit of the poisonous tree" doctrine may extend to derivative evidence.
Motions to suppress are filed before trial and decided at a suppression hearing where the judge acts as factfinder. The defense bears the initial burden of demonstrating a constitutional violation, after which the burden shifts to the government to prove the evidence was lawfully obtained. Common grounds include warrantless searches without valid exceptions, Miranda violations during custodial interrogation, illegal traffic stops lacking reasonable suspicion, and identification procedures that were unduly suggestive. A successful suppression motion can be case-dispositive if the excluded evidence is central to the prosecution.
Attorney: "Your Honor, the defense moves to suppress all evidence seized from Mr. Thompson's vehicle. The officers lacked probable cause for the search and no exception to the warrant requirement applies."
Judge: "Officer Martinez, what facts gave you probable cause to believe contraband was in the vehicle?" Officer: "I observed a clear plastic bag protruding from under the seat during a lawful traffic stop."
Attorney: "We also move to suppress the defendant's statements. He was in custody and was not advised of his Miranda rights before questioning." Prosecution: "Your Honor, the defendant was not in custody. He was free to leave at any time."
Students often conflate a motion to suppress with a motion in limine. A motion to suppress is based on constitutional violations (illegal search, Miranda violation), while a motion in limine addresses evidence that is legally obtained but potentially inadmissible under evidentiary rules.
Federal suppression applies the exclusionary rule with exceptions like good faith (United States v. Leon, 1984). Some states provide broader suppression protections under their own constitutions — for example, some reject the good faith exception or have stricter standards for consent searches.
Mapp v. Ohio, 367 U.S. 643 (1961)
Applied the exclusionary rule to the states, holding that unconstitutionally obtained evidence must be suppressed in state criminal proceedings.
Wong Sun v. United States, 371 U.S. 471 (1963)
Established the fruit of the poisonous tree doctrine, requiring suppression of all evidence derived from an initial constitutional violation.
United States v. Leon, 468 U.S. 897 (1984)
Created the good-faith exception to the exclusionary rule for officers reasonably relying on a facially valid warrant.
| Motion to Suppress | Motion in Limine |
|---|---|
| Based on constitutional violations (4th/5th Amendment) | Based on evidentiary rules (relevance, prejudice) |
| Primarily used in criminal cases | Used in both criminal and civil cases |
| Invokes the exclusionary rule | Invokes Rules of Evidence (e.g., Rules 403, 404) |
| Requires an evidentiary hearing | Often decided on briefs without testimony |
| Challenges how evidence was obtained | Challenges admissibility regardless of how obtained |
When must a motion to suppress be filed?
Typically before trial as part of pretrial motions. Under FRCP 12(b)(3), motions to suppress must be raised prior to trial or they are waived, unless the court grants relief for good cause.
What is the burden of proof on a motion to suppress?
Without a warrant, the prosecution bears the burden of proving an exception applies. With a warrant, the defendant bears the initial burden of showing a deficiency. The ultimate burden rests with the government.
What is the fruit of the poisonous tree doctrine?
Under Wong Sun, evidence derived from an unlawful search is inadmissible. Exceptions include independent source, inevitable discovery, and attenuation of the taint.
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