tion of a conversation was a seizure.

The second of the Olmstead holdings—where there is no physical trespass, there can be no search—fell that same year. In Katz v. United States (1967), the Court considered the case of Charles Katz, who had used a pay phone in Los Angeles to place illegal bets in Miami and Boston. Without obtaining a warrant, FBI agents placed listening devices outside of the phone booth and recorded Katz’ end of several conversations. The transcripts of these conversations were introduced during Katz’ trial, and presumably played a role in his conviction. In response to his appeal, the Supreme Court ruled that tapping phone calls placed from a phone booth required a warrant. The majority opinion explicitly overturned Olmstead, holding that the Fourth Amendment “protects people, not places;” trespass was no longer necessary for the Fourth Amendment to be implicated.

Justice Harlan’s concurring opinion introduced a two-part test for determining whether the Fourth Amendment should be applied in a given situation:

˲ ˲ The person must have exhibited “an actual (subjective) expectation of privacy;”

˲ ˲ This expectation is one that “society is prepared to recognize as reasonable.” Thus by 1967 Olmstead was completely reversed, and the Court was applying Fourth Amendment protection to the content of telephone calls. However, the context of telephone and other electronic communication did not receive the same level of protection.

Context. The distinction between the content and context of electronic communication is best understood through the analogy of postal mail. The content information is the letter itself—the written or typed communication generated by one party for the purpose of communicating with another party. As with the content of a telephone call, letters are protected by a series of rather strict regulations.a The context information consists of the information on the outside of the envelope, information used by the com- a See Ex Parte Jackson, 96 U.S. ( 6 Otto) 727, 733 (1877); Walter v. United States, 447 U.S. 649, 651 (1980).

The surveillance
architecture
adopted for cellular
networks generates
a pool of data that
feeds into law
enforcement’s
and marketers’
desire for personal
information.

munication system to establish communication between the two parties. In the case of the postal system, this consists primarily of the mailing and return addresses, but may also include postmarks or other information that accumulates in transit. In the case of a cellular telephone call, context data includes the number the caller dials, the number from which the caller dials, the location of the caller, the time of the call, and its duration.

Courts and legislatures have been far less protective of context information than content. The basic rationale is that the user understands context information is needed to complete the communication process, and that in using the technology, context information is freely given to the network. It follows that, according to the courts, there is no reasonable expectation of privacy in this information, and the Fourth Amendment is not implicated.

The key precedent is United States v. Miller (1976), a case with far reaching implications for the public use of a wide variety of communication networks. The case involved a modern-day bootlegger named Mitch Miller; prohibition was not the issue, the focus was instead on the more mundane matter of taxation. While putting out a fire at Miller’s warehouse, firefighters and police discovered 175 gallons of whiskey that did not have the requisite tax stamps. Investigators obtained, without a warrant, copies of Miller’s deposit slips and checks. The cancelled checks showed that Miller had purchased material for the construction of a still. Miller was subsequently convicted of possessing an unregistered still.

Miller appealed, claiming that his Fourth Amendment rights had been violated; the investigators should have obtained a warrant before acquiring his bank records. The Supreme Court disagreed. Writing for the Court, Justice Powell stated that:

 

There is no legitimate “expectation of privacy” in the contents of the original checks and deposit slips, since the checks are not confidential communications, but negotiable instruments to be used in commercial transactions, and all the documents obtained contain only in-