Mapp Hearing
A Mapp hearing is a court hearing in a criminal case to determine whether evidence being used against the defendant was obtained illegally. The Fourth Amendment provides that defendants are to be free from unreasonable searches and seizures. As such, there is a presumption that the police must get a warrant before searching a person or place for evidence. Under the landmark case Mapp v. Ohio, the United States Supreme Court held that evidence had to be excluded, or suppressed, if it was obtained contrary to the Fourth Amendment. 367 U.S. 643, 655 (1961). In Mapp, Dollree Mapp was charged with possession of obscene material in state court following an admittedly illegal search. Ohio police officers had forced their way into Ms. Mapp's home while investigating a different matter and found the material. After the Ohio Supreme Court found that the conviction was valid despite the evidence being obtained illegally, the United States Supreme Court reversed.
In a criminal case, a Mapp hearing may be held to determine whether evidence that the prosecution wishes to use was obtained illegally. Should the evidence be found to be obtained illegally, the prosecution cannot use it against the defendant to prove their guilt. In many cases, this means the criminal case will continue to trial without the illegally obtained evidence. In other cases, the prosecution can lose the ability to present evidence sufficient to proceed, and the case may be dismissed or, should there be a trial, end in acquittal.