Eyewitness Identification: Constitutional Aspects

The Supreme Court has held that a person does not have a reasonable expectation of privacy in personal characteristics that are exposed to the public, such as one's visage or the sound of one's voice (United States v. Dionisio, 410 U.S. 1, 14 (1973)). Thus, viewing a face in a lineup or showup is not a "search" for purposes of the Fourth Amendment prohibition of unreasonable searches and seizures. However, the Court has also held that the police "seizure" of a person for the purpose of subjecting him or her to an identification procedure does implicate the Fourth Amendment (Hayes v. Florida, 470 U.S. 811, 816 (1985); Davis v. Mississippi, 394 U.S. 721, 724 (1969)). Under these circumstances, the police need, at a minimum, reasonable suspicion that the person is involved in the crime, unless the person is being used as a distractor and is already in custody, in which case no suspicion is necessary.