In Bumper v. North Carolina, 391 U.S. 543 (1968), the Court found that a search conducted by virtue of a warrant cannot later be justified by consent if the warrant turns out to be invalid. Voluntariness of consent to search is to be determined from the totality of the circumstances of which consent is one element, according to Schneckloth v. Bustamonte, 412 U.S. 218 (1973). Knowledge of the right to refuse consent is not a prerequisite for voluntary consent. It was determined in the case U.S. v. Watson, 423 U.S. 411 (1976), that an officer may arrest an individual in a public place without a warrant, even if there is time and opportunity to obtain one, if there is probable cause that a criminal act has been committed. The Court found in Stoner v. California, 376 U.S. 483 (1964), that a hotel guest is entitled to protection against unreasonable searches and seizures; this cannot be waived by the consent of a hotel clerk.