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The Fourth Amendment and the 'Exclusionary Rule'

The Fourth Amendment to the U.S. Constitution prohibits police officers from conducting unreasonable searches and seizures by requiring them to either have a valid warrant or probable cause. But, what happens if a police officer does conduct a search in violation of the Fourth Amendment and subsequently finds incriminating evidence? Well, that's when the "exclusionary rule" comes into play.

Read on the learn how this rule developed and why we have such a rule in the first place.

The Development of the Exclusionary Rule

For the more than 100 years after its ratification, the Fourth Amendment was of little value to criminal defendants because evidence seized by law enforcement in violation of the warrant or reasonableness requirements was still admissible during the defendant's prosecution.

The U.S. Supreme Court dramatically changed Fourth Amendment jurisprudence in 1914, however, when it handed down its decision in Weeks v. United States. This case involved the appeal of a defendant who had been convicted based on evidence that had been seized by a federal agent without a warrant or other constitutional justification. In reversing the conviction, the Supreme Court effectively created the exclusionary rule. Then, in 1961, the U.S. Supreme Court made the exclusionary rule applicable to the states with its decision in Mapp v. Ohio.

Why Do We Have the Exclusionary Rule?

Designed to deter police misconduct, the exclusionary rule enables courts to exclude incriminating evidence from being introduced at trial upon proof that the evidence was procured in violation of a constitutional provision. The rule allows defendants to challenge the admissibility of evidence by bringing a pre-trial motion to suppress the evidence. If the court allows the evidence to be introduced at trial and the jury votes to convict, the defendant can challenge the propriety of the trial court's decision denying the motion to suppress on appeal.

If the defendant succeeds on appeal, however, the U.S. Supreme Court has ruled that double jeopardy principles do not bar retrial of the defendant because the trial court's error wasn't addressing the question of guilt or innocence. Nonetheless, obtaining a conviction in the second trial would be significantly more difficult if the evidence suppressed by the exclusionary rule is important to the prosecution.

Companion to the Exclusionary Rule: Fruit of the Poisonous Tree

A legal concept that's related to the exclusionary rule is the "fruit of the poisonous tree" doctrine. Under this doctrine, a court may exclude from trial not only evidence that itself was seized in violation of the U.S. Constitution, but also any other evidence that is derived from an illegal search.

For example, suppose a defendant is arrested for kidnapping and later confesses to the crime. If a court subsequently declares that the arrest was unconstitutional, the confession will also be deemed tainted and ruled inadmissible at any prosecution of the defendant on the kidnapping charge.

Learn More About the Fourth Amendment and the Exclusionary Rule: Speak with an Attorney

If you're facing criminal charges, the exclusionary rule could end up determining the outcome of your case. However, courts do not automatically exclude evidence unlawfully obtained by law enforcement. Instead, it's up to your legal defense team to evaluate the evidence and make the appropriate objections. That's why it's critical to have a strong criminal defense lawyer from the very start of your case.

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