Smith v. Maryland

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Smith v. Maryland
Argued March 28, 1979
Decided June 20, 1979
Full case nameMichael Lee Smith v. Maryland
Citations442 U.S. 735 (more)
99 S. Ct. 2577; 61 L. Ed. 2d 220; 1979 U.S. LEXIS 134
Case history
PriorSmith v. State, 283 Md. 156, 389 A.2d 858 (1978); cert. granted, 439 U.S. 1001 (1978).
The installation and use of a pen register is not a "search" within the meaning of the Fourth Amendment, and hence no warrant is required.
Court membership
Chief Justice
Warren E. Burger
Associate Justices
William J. Brennan Jr. · Potter Stewart
Byron White · Thurgood Marshall
Harry Blackmun · Lewis F. Powell Jr.
William Rehnquist · John P. Stevens
Case opinions
MajorityBlackmun, joined by Burger, White, Rehnquist, Stevens
DissentStewart, joined by Brennan
DissentMarshall, joined by Brennan
Powell took no part in the consideration or decision of the case.

Smith v. Maryland, 442 U.S. 735 (1979), was a Supreme Court case, holding that the installation and use of a pen register was not a "search" within the meaning of the Fourth Amendment to the United States Constitution, and hence no warrant was required.[1]

The pen register was installed on telephone company property at the telephone company's central offices. In a majority opinion, Justice Harry Blackmun rejected the idea that the installation and use of a pen register constitutes a violation of the "legitimate expectation of privacy" since the telephone numbers would be available to and recorded by the phone company anyway.


In Katz v. United States, the United States Supreme Court established its "reasonable expectation of privacy" test,[2] which overturned a 1928 precedent established in Olmstead v. United States[3] and held that the use of a covert listening device (bug) was not a constitutionally protected search without first obtaining a warrant, because there was a reasonable expectation that the communication would be private. The government was therefore 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 that they could connect his call, he could not reasonably expect that the numbers he dialed were private. 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 legal basis for privacy protection of the information contained in a pen register, it would have to be enacted by Congress as statutory privacy law.

Majority opinion[edit]

In a majority opinion authored by Justice Harry Blackmun, the court held 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 it 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.

Dissenting opinions[edit]

In a dissenting opinion, Justice Potter Stewart, joined by Justice William J. Brennan, Jr., instead argued that, like the contents of a conversation (an allusion to a precedent set by Katz), the record of numbers dialed from a private telephone is within constitutional protection:

The central question in this case is whether a person who makes telephone calls from his home is entitled to make a similar assumption about the numbers he dials. What the telephone company does or might do with those numbers is no more relevant to this inquiry than it would be in a case involving the conversation itself. It is simply not enough to say, after Katz, that there is no legitimate expectation of privacy in the numbers dialed because the caller assumes the risk that the telephone company will disclose them to the police.

The numbers dialed from a private telephone—although certainly more prosaic than the conversation itself—are not without "content."

In a second dissenting opinion, Justice Thurgood Marshall, joined by Justice Brennan, expressed his disagreement with the Court's existing third-party doctrine, stating:

Since I remain convinced that constitutional protections are not abrogated whenever a person apprises another of facts valuable in criminal investigations, see, e.g., United States v. White, 401 U.S. 745, 786–790 (1971) (Harlan, J., dissenting); id., at 795–796 (MARSHALL, J., dissenting); California Bankers Assn. v. Shultz, 416 U.S. 21, 95–96 (1974) (MARSHALL, J., dissenting); United States v. Miller, 425 U.S. 435, 455–456 (1976) (MARSHALL, J., dissenting), I respectfully dissent.

The use of pen registers, I believe, constitutes such an extensive intrusion. To hold otherwise ignores the vital role telephonic communication plays in our personal and professional relationships, see Katz v. United States, 389 U.S., at 352, as well as the First and Fourth Amendment interests implicated by unfettered official surveillance. Privacy in placing calls is of value not only to those engaged in criminal activity. The prospect of unregulated governmental monitoring will undoubtedly prove disturbing even to those with nothing illicit to hide. Many individuals, including members of unpopular political organizations or journalists with confidential sources, may legitimately wish to avoid disclosure of their personal contacts. See NAACP v. Alabama, 357 U.S. 449, 463 (1958); Branzburg v. Hayes, 408 U.S. 665, 695 (1972); id., at 728–734 (STEWART, J., dissenting). Permitting governmental access to telephone records on less than probable cause may thus impede certain forms of political affiliation and journalistic endeavor that are the hallmark of a truly free society. Particularly given the Government's previous reliance on warrantless telephonic surveillance to trace reporters' sources and monitor protected political activity, I am unwilling to insulate use of pen registers from independent judicial review. [442 U.S. 735, 752]

See also[edit]


  1. ^ Smith v. Maryland, 442 U.S. 735 (1979).
  2. ^ Katz v. United States, 389 U.S. 347 (1967).
  3. ^ Olmstead v. United States, 277 U.S. 438 (1928).

Further reading[edit]

  • Applegate, John; Grossman, Amy (1980). "Pen Registers after Smith v. Maryland". Harv. C.R.-C.L. L. Rev. 15 (3): 753–778.
  • Andrea Peterson from The Washington Post's The Switch in a December 4, 2013, article named "The NSA says it ‘obviously’ can track locations without a warrant. That’s not so obvious." discussed the background of the case.

External links[edit]