• No part of the Constitution explicitly refers to privacy
• But the Bill of Rights protects certain aspects of privacy
• Courts have viewed Fourth Amendment as partial guarantee of privacy

The Constitution provides a second type of privacy protection. This protection is not explicit, since no clause in the Constitution refers expressly to privacy. But the courts have repeatedly recognized that the Constitution does expressly protect certain aspects of privacy under the Bill of Rights. These include a right to privacy of belief as guaranteed under the First Amendment and a right to privacy within our homes as guaranteed under the Third Amendment. But perhaps the most concrete of the privacy rights suggested by the Bill of Rights are those covered by the Fourth Amendment—the right to be secure in our persons and property against unreasonable searches and seizures.

The Fourth Amendment was written with a very specific British practice in mind. Prior to the Revolution, British customs officers used writs of assistance to indiscriminately search colonists' homes and vessels for smuggled goods. These writs were not like contemporary search warrants; they were not specific as to the place or purpose of the search. Nor were they limited in terms of time. In fact, writs of assistance were issued for the life of the sovereign. As a result, writs functioned as blanket search warrants authorizing, in the eyes of the colonists, unreasonable intrusions into their homes and property.

The Fourth Amendment, drafted in 1789, made explicit reference to these old writs. In its second clause it specified that "no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized." But the amendment's first clause spoke to a more general "right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures." This more general right was tied to an ancient British legal principle guaranteeing personal security in our homes. The belief that "every man's home is his castle" was firmly entrenched in British law.

The courts have spent a great deal of time sorting out exactly what this more general right entails. As a general rule, the courts have maintained that warrants must be obtained before conducting searches. But they have also established certain exceptions to this rule. For example, the police do not need to obtain a warrant before searching a person while in "hot pursuit." Nor is a warrant required in order to search a car or home when something illegal lies in "plain view." In addition, a warrant is not necessary to search a person, and the area surrounding that person, while being placed under arrest.

But the courts have not been able to define with great precision what constitutes the "surrounding area" subject to a warrantless search. And other particular circumstances constantly arise to challenge the courts in their efforts to flesh out the protections of the Fourth Amendment. For example, the introduction of electronic surveillance technologies forced the courts to consider just exactly what constituted a search. Initially, the Supreme Court held that wiretaps did not constitute a search because there was no actual invasion of a person's private space. But in 1967, in Katz v. United States, the Court reversed itself and held that wiretaps do constitute a form of search subject to Fourth Amendment regulation—that is, the police must obtain a warrant before tapping a phone, even if, as in this case, the phone was in a public booth.

Critical to the Court's decision in this case was its conclusion that the Fourth Amendment protects people, not just places; the amendment's intent was not just to protect our homes and property from government's unreasonable encroachment, but also people and the privacy that they have come to expect in certain places and situations. More precisely, the Court held that when and where there is a reasonable expectation of privacy, that privacy must be respected. It cannot be violated unreasonably; authorities may encroach upon it only with a warrant or by meeting one of the exceptions that authorize a warrantless search.

The Katz case illustrates how the Fourth Amendment has evolved over the past two hundred years. While the Fourth Amendment was inspired by a specific British practice, it was drafted in terms suggesting that its framers wanted to establish a more fundamental protection against government intrusion. And as this protection has been worked out by the courts, it has become synonymous with a guarantee that the government may not intrude upon those places, circumstances, and conversations where there is a reasonable expectation of privacy.