Potter Stewart

“ Denno, 388 U.S. 293, 301, 87 S.Ct. 1967, 1972, 18 L.Ed.2d 1199, the fact that the parties involved in the decision are the only litigants so situated who receive the benefit of the new rule is 'an unavoidable consequence of the necessity that constitutional adjudications not stand as mere dictum.' Whatever inequity may arguably result from applying the new rule to those 'chance beneficiaries' is 'an insignificant cost for adherence to sound principles of decision-making.' Ibid. ”

“ Last Term in Katz v. United States, 389 U.S. 347, 88 S.Ct. 507, 19 L.Ed.2d 576, we held that the reach of the Fourth Amendment 'cannot turn upon the presence or absence of a physical intrusion into any given enclosure.' Id., at 353, 88 S.Ct., at 512. Noting that the 'Fourth Amendment protects people, not places,' id., at 351, 88 S.Ct., at 511, we overruled cases holding that a search and seizure of speech requires some trespass or actual penetration of a particular enclosure. ”

“ There is, moreover, a significant distinction between the Mapp and Katz decisions. Mapp dealt solely with the applicability of the exclusionary rule to the States; 'the situation before Mapp * * * (was that) the States at least knew that they were constitutionally forbidden from engaging in unreasonable searches and seizures under Wolf v. Colorado, 338 U.S. 25, 69 S.Ct. 1359, 93 L.Ed. 1782 (1949) .' [22] Before Katz on the other hand, 'non-trespassory' electronic surveillance was not thought to fall within the reach of the Fourth Amendment. ”

“ Although there apparently have not been many federal convictions based on evidence gathered by warrantless electronic surveillance, [17] we have no cause to doubt that the number of state convictions obtained in reliance on pre-Katz decisions is substantial. [18] Moreover, the determination of whether a particular instance of eavesdropping led to the introduction of tainted evidence at trial would in most cases be a difficult and time-consuming task, which, particularly when attempted long after the event, would impose a weighty burden on any court. ”

“ The petitioners argue that even if Katz is not given fully retrospective effect, at least it should govern those cases which, like the petitioners', were pending on direct review when Katz was decided. Petitioners point out that in Linkletter, the only other case involving the retroactivity of a Fourth Amendment decision, the Court held Mapp applicable to every case still pending on direct review on the date of that decision. A similar approach was adopted in Tehan v. United States ex rel. Shott, 382 U.S. 406, 86 S.Ct. 459, 15 L.Ed.2d 453, with respect to the prospectivity of Griffin v. ”

“ United States ex rel. Shott, 382 U.S. 406, 417, 86 S.Ct. 459, 466, 15 L.Ed.2d 453.↑ Indeed, since the Fourth Amendment prohibits only Unreasonable searches and seizures, it could be argued that there was, in fact, no Fourth Amendment viotion in the present case. The law enforcement officers could certainly be said to have been acting 'reasonably' in measuring their conduct by the relevant Fourth Amendment decisions of this Court. Cf. Katz v. United States, 389 U.S. 347, 356, 88 S.Ct. 507, 514, 19 L.Ed.2d 576; James v. United States, 366 U.S. 213, 221-222, 245 81 S.Ct. ”