Legal Definitions - exclusionary rule

The exclusionary rule is a legal principle that prevents the government from using evidence in a criminal trial if that evidence was obtained in a way that violates a person's constitutional rights. Its primary purpose is to deter law enforcement officers from engaging in illegal searches, seizures, or questioning, thereby upholding fundamental protections like the Fourth Amendment (protection against unreasonable searches and seizures), the Fifth Amendment (right against self-incrimination), and the Sixth Amendment (right to an attorney).

If evidence is obtained unlawfully, and that unlawful evidence then directly leads to the discovery of other evidence, that "secondary" evidence is also typically excluded under what is known as the "fruit of the poisonous tree" doctrine. While there are some exceptions to this rule, its fundamental aim is to ensure that the government respects constitutional protections during criminal investigations.

Here are some examples illustrating the exclusionary rule:

• Example 1 (Illegal Search): Police officers, without a search warrant or any immediate danger, force their way into a person's apartment because they suspect drug activity. Inside, they find a large quantity of illegal narcotics.

  Explanation: The forced entry without a warrant or valid reason constitutes an unreasonable search, violating the Fourth Amendment. Under the exclusionary rule, the illegal narcotics found during this search would not be allowed as evidence in court against the apartment's occupant, because they were obtained unlawfully.

• Example 2 (Violation of Miranda Rights): A suspect is arrested for theft and taken to the police station. Detectives interrogate the suspect for several hours, repeatedly asking questions about the crime, but never inform them of their right to remain silent or their right to an attorney (their Miranda rights). During this interrogation, the suspect eventually confesses to the theft.

  Explanation: The confession was obtained after the suspect's Fifth Amendment right against self-incrimination was violated because they were not properly informed of their Miranda rights before questioning. The exclusionary rule would prevent the prosecution from using this confession as evidence in court.

• Example 3 (Fruit of the Poisonous Tree): Following an illegal wiretap (a violation of the Fourth Amendment) on a suspect's phone, law enforcement overhears a conversation where the suspect mentions hiding stolen artwork in a specific storage unit. Based solely on this illegally obtained information, officers obtain a search warrant for the storage unit and find the artwork.

  Explanation: The initial illegal wiretap is the "poisonous tree" because it violated the suspect's constitutional rights. The information gained from this wiretap directly led to the discovery of the stolen artwork. Even though a warrant was later obtained for the storage unit, the evidence (the artwork) is considered "fruit of the poisonous tree" and would likely be excluded from trial because its discovery stemmed directly from the initial illegal act.