Abstract: In the early twentieth century, the Supreme Court's Fourth Amendment jurisprudence was geared toward the protection of property. The Court's inclination to protect property quite clearly is reflected in its 1928 decision in Olmstead v. United States (277 U.S. 438 (1928)). In Olmstead, the Supreme Court held that use of a wiretap to intercept a private telephone conversation was not a "search" for purposes of the Fourth Amendment. One of the grounds on which the Court justified its result was that there had been no physical intrusion into the person's home. Under Olmstead's narrow view of the Fourth Amendment, the amendment was not applicable in the absence of physical intrusion. Thus, without trespass or seizure of any material object, surveillance was beyond the scope of the Fourth Amendment as interpreted by the Olmstead Court.
However, in its well-known decision in Katz v. United States, 389 U.S. 347 (1967), the Supreme Court rejected Olmstead's "trespass" doctrine, articulating, in its place, a Fourth Amendment jurisprudence based on the protection of individual privacy. In Katz, the Court held that the Fourth Amendment protects people, not places: "What a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection¼ But what he seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected."
Thus, the Court held that physical penetration of a constitutionally protected area is not necessary before a search and seizure can be held to violate the Fourth Amendment. According to the Court in Katz, "once it is recognized that the Fourth Amendment protects people-and not simply "areas"-against unreasonable searches and seizures it becomes clear that the reach of that Amendment cannot turn upon the presence or absence of a physical intrusion into any given enclosure." Thus, although the Government's activities in Katz involved no physical intrusion, they were found to have violated the privacy on which the petitioner justifiably relied and thus constituted "search and seizure" within the meaning of the 4th Amendment. Changing technology precipitated the shift from protection of property to protection of privacy, and in 1968, just one year after Katz, Congress passed Title III of the Omnibus Crime Control and Safe Streets Act authorizing microphone surveillance or wiretapping for law enforcement purposes, and requiring a warrant, based on probable cause, prior to such surveillance or wiretapping.