Smith v. Maryland

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Smith v. Maryland
Seal of the United States Supreme Court.svg
Argued March 28, 1979
Decided June 20, 1979
Full case name Michael Lee Smith v. Maryland
Citations 442 U.S. 735 (more)
99 S. Ct. 2577; 61 L. Ed. 2d 220; 1979 U.S. LEXIS 134
Prior history Cert. to the Court of Appeals of Maryland
Court membership
Case opinions
Majority Blackmun, joined by Burger, White, Rehnquist, Stevens
Dissent Stewart, joined by Brennan
Dissent Marshall, joined by Brennan
Powell took no part in the consideration or decision of the case.

Smith v. Maryland, 442 U.S. 735 (1979),[1] was a case in which the Supreme Court of the United States held that the installation and use of the pen register was not a "search" within the meaning of the Fourth Amendment, and hence no warrant was required. The pen register was installed on telephone company property at the telephone company's central offices. In the Majority opinion, Justice Blackmun rejected the idea that the installation and use of a pen register constitutes a violation of the "legitimate expectation of privacy" since the numbers would be available to and recorded by the phone company anyway.


In Katz v. United States (1967), the United States Supreme Court established its "reasonable expectation of privacy" test. It overturned Olmstead v. United States and held that a bugging was a constitutionally-protected search, because there was a reasonable expectation that the communication would be private. The government was then required to get a warrant to execute a search using a bug.

In Smith v. Maryland, the Supreme Court held that a pen register is not a search because the "petitioner voluntarily conveyed numerical information to the telephone company." Since the defendant had disclosed the dialed numbers to the telephone company so they could connect his call, he did not have a reasonable expectation of privacy in the numbers he dialed. The court did not distinguish between disclosing the numbers to a human operator or just the automatic equipment used by the telephone company.

The Smith decision left pen registers completely outside constitutional protection. If there were to be any privacy protection, it would have to be enacted by Congress as statutory privacy law.

Court Opinion[edit]

The justices that held the decision argued that:

Given a pen register's limited capabilities, therefore, petitioner's argument that its installation and use constituted a "search" necessarily rests upon a claim that he had a "legitimate expectation of privacy" regarding the numbers he dialed on his phone.

This claim must be rejected. First, we doubt that people in general entertain any actual expectation of privacy in the numbers they dial. All telephone users realize that they must "convey" phone numbers to the telephone company, since it is through telephone company switching equipment that their calls are completed. All subscribers realize, moreover, that the phone company has facilities for making permanent records of the numbers they dial, for they see a list of their long-distance (toll) calls on their monthly bills. In fact, pen registers and similar devices are routinely used by telephone companies "for the purposes of checking billing operations, detecting fraud, and preventing violations of law." United States v. New York Tel. Co., 434 U.S., at 174 -175.

Further it was argued that is not unreasonable to assume that the telephone company would use electronic equipment to keep records of all telephone numbers dialed.

Electronic equipment is used not only to keep billing records of toll calls, but also "to keep a record of all calls dialed from a telephone which is subject to a special rate structure."

The argument was made that since telephone numbers are needed to connect your calls that this information cannot be considered private as telephone companies would have access to this information in order to connect your call.

Telephone users, in sum, typically know that they must convey numerical information to the phone company; that the phone company has facilities for recording this information; and that the phone company does in fact record this information for a variety of legitimate business purposes. Although subjective expectations cannot be scientifically gauged, it is too much to believe that telephone subscribers, under these circumstances, harbor any general expectation that the numbers they dial will remain secret.

See also[edit]


  1. ^ 442 U.S. 735 Full text of the opinion courtesy of

Further reading[edit]