A more thorough explanation:

The exclusionary rule is a legal principle that prevents the government from using evidence that was obtained in violation of the United States Constitution. This rule applies to evidence that was gathered through an unreasonable search or seizure, in violation of the Fourth Amendment. It also applies to self-incriminatory statements obtained in violation of the Fifth Amendment and evidence obtained in violation of the Sixth Amendment right to counsel.

If evidence that falls within the scope of the exclusionary rule leads law enforcement to other evidence, which they would not otherwise have located, then the exclusionary rule applies to the newly discovered evidence. This secondarily excluded evidence is called “fruit of the poisonous tree.”

The exclusionary rule is a court-created remedy and deterrent, not an independent constitutional right. Its purpose is to deter law enforcement officers from conducting searches or seizures in violation of the Fourth Amendment and to provide remedies to defendants whose rights have been infringed.

There are several exceptions to the exclusionary rule:

• Good Faith Exception: Evidence is not excluded if it is obtained by officers who reasonably rely on a search warrant that turns out to be invalid. This exception does not trigger the rule because excluding the evidence would not deter police officers from violating the law in the future.
• Independent Source Doctrine: Evidence initially obtained during an unlawful search or seizure may later be admissible if the evidence is later obtained through a constitutionally valid search or seizure.
• Inevitable Discovery Doctrine: This doctrine allows admission of evidence that was discovered in an unlawful search or seizure if it would have been discovered in the same condition anyway, by an independent line of investigation that was already being pursued when the unlawful search or seizure occurred.
• Attenuation Doctrine: In cases where the relationship between the evidence challenged and the unconstitutional conduct is too remote and attenuated, the evidence may be admissible.
• Evidence Admissible for Impeachment: The exclusionary rule does not prevent the government from introducing illegally gathered evidence to “impeach,” or attack the credibility of, defendants’ testimony at trial.
• Qualified Immunity: Due to qualified immunity, the exclusionary rule is often a defendant's only remedy when police officers conduct an unreasonable search or violate their Miranda rights.

For example, the good faith exception allows evidence to be admissible if it is obtained by officers who reasonably rely on a search warrant that turns out to be invalid. This exception does not trigger the exclusionary rule because excluding the evidence would not deter police officers from violating the law in the future.