The rights of those accused of a crime are spelled out in four of the ten constitutional amendments that make up the Bill of Rights (Amendments Four, Five, Six, and Eight). For the most part, these amendments have been held to apply to both the federal and the state governments. The Fourth Amendment says in part that “the right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated.” Although there are numerous and tricky exceptions to the general rule, ordinarily the police may not break into a person’s house or confiscate his papers or arrest him unless they have a warrant to do so. This means, for instance, that a policeman cannot simply stop you on a street corner and ask to see what is in your pockets (a power the police enjoy in many other countries), nor can your home be raided without probable cause to believe that you have committed a crime. What if the police do search or seize unreasonably?
The courts have devised a remedy for the use at trial of the fruits of an unlawful search or seizure. Evidence that is unconstitutionally seized is excluded from the trial. This is the so-called exclusionary rule, first made applicable in federal cases in 1914 and brought home to the states in 1961. The exclusionary ruleis highly controversial, and there are numerous exceptions to it. But it remains generally true that the prosecutor may not use evidence willfully taken by the police in violation of constitutional rights generally, and most often in the violation of Fourth Amendment rights. (The fruits of a coerced confession are also excluded.)