What does the exclusionary rule prevent?

The exclusionary rule is a legal principle in United States law that prevents the government from using evidence gathered in violation of the Constitution, particularly the Fourth Amendment, which safeguards against unreasonable searches and seizures. When evidence is obtained illegally, such as through an unlawful search or a lack of probable cause, this rule mandates that such evidence cannot be presented in a trial. The purpose of the exclusionary rule is to deter law enforcement from conducting illegal searches, thereby upholding constitutional rights.

The other options do not accurately describe the exclusionary rule. For instance, hearsay evidence is a separate category governing the admissibility of statements made outside of court, and while important, it does not fall under the exclusionary rule. Public demonstrations against a verdict pertain to First Amendment rights and are not related to evidence admissibility. Lastly, a conviction based solely on witness testimony may raise concerns of credibility or reliability, but it is not directly addressed by the exclusionary rule, which specifically pertains to the legality of how evidence is obtained.