What is the exclusionary rule regarding evidence in a criminal trial?

The exclusionary rule is a legal principle that prohibits the use of evidence obtained through violations of a defendant's constitutional rights, most commonly violations of the Fourth Amendment, which protects against unreasonable searches and seizures. When evidence is acquired through illegal means, such as without a proper warrant or probable cause, it cannot be used to prosecute an individual in court.

This rule is intended to deter law enforcement from conducting unlawful searches and seizures, thereby upholding the integrity of the judicial process. If the prosecution were allowed to use such evidence, it could incentivize police misconduct and undermine the rights afforded to individuals under the Constitution. By excluding illegally obtained evidence, the rule seeks to maintain fair trial standards and protect civil liberties within the criminal justice system.