442 U.S. 735 (1979).

One-Sentence TakeawayThere is no reasonable expectation of privacy in numbers dialed from a phone and, therefore, it did not violate the Fourth Amendment for the officers to install and use a pen register without first obtaining a warrant.

Police officers had reasons to believe that Defendant had robbed the victim and was now making threatening calls to her home.  The officer requested the phone company install a pen register to record the numbers dialed from Defendant’s home.  The police did not obtain a warrant prior to making the request.

Based on the information obtained from the pen register, the officers obtained a search warrant and obtained evidence which led to Defendant’s conviction for robbery.

The issue facing the U.S. Supreme Court was whether the warrantless installation of the pen register violate Defendant’s Fourth Amendment right to privacy.  The Court answered in the negative.

The Court reasoned, “this Court uniformly has held that the application of the Fourth Amendment depends on whether the person invoking its protection can claim a ‘justifiable,’ a ‘reasonable,’ or a ‘legitimate expectation of privacy’ that has been invaded by government . . . This inquiry . . . embraces two discrete questions.  The first is . . . whether . . . the individual has shown that ‘he seeks to preserve [something] as private.’ The second question is whether the individual’s subjective expectation of privacy is ‘one that society is prepared to recognize as ‘reasonable.'”

The Court reasoned that Defendant here did not have a reasonable expectation of privacy.  “Since the pen register was installed on telephone company property at the telephone company’s central offices, petitioner obviously cannot claim that his ‘property’  was invaded or that police intruded into a ‘constitutionally protected area’  Pen registers do not acquire the contents of communications.”

The Court further explained: ” 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 . . . It is too much to believe that telephone subscribers, under these circumstances, harbor any general expectation that the numbers they dial will remain secret.”

“Second, even if petitioner did harbor some subjective expectation that the phone numbers he dialed would remain private, this expectation is not one that society is prepared to recognize as reasonable.  This Court consistently has held that a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties . . . We therefore conclude that petitioner in all probability entertained no actual expectation of privacy in the phone numbers he dialed, and that, even if he did, his expectation was not legitimate.  The installation and use of a pen register, consequently, was not a search.”

Further Reading:

Supreme Court Syllabus:

The telephone company, at police request, installed at its central offices a pen register to record the numbers dialed from the telephone at petitioner’s home. Prior to his robbery trial, petitioner moved to suppress “all fruits derived from” the pen register. The Maryland trial court denied this motion, holding that the warrantless installation of the pen register did not violate the Fourth Amendment. Petitioner was convicted, and the Maryland Court of Appeals affirmed.

Held: 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. Pp. 442 U. S. 739-746.

(a) Application of the Fourth Amendment depends on whether the person invoking its protection can claim a “legitimate expectation of privacy” that has been invaded by government action. This inquiry normally embraces two questions: first, whether the individual has exhibited an actual (subjective) expectation of privacy; and second, whether his expectation is one that society is prepared to recognize as “reasonable.” Katz v. United States, 389 U. S. 347. Pp. 442 U. S. 739-741.

(b) Petitioner in all probability entertained no actual expectation of privacy in the phone numbers he dialed, and even if he did, his expectation was not “legitimate.” First, it is doubtful that telephone users in general have any expectation of privacy regarding the numbers they dial, since they typically know that they must convey phone numbers to the telephone company and that the company has facilities for recording this information and does, in fact, record it for various legitimate business purposes. And petitioner did not demonstrate an expectation of privacy merely by using his home phone, rather than some other phone, since his conduct, although perhaps calculated to keep the contents of his conversation private, was not calculated to preserve the privacy of the number he dialed. Second, even if petitioner did harbor some subjective expectation of privacy, this expectation was not one that society is prepared to recognize as “reasonable.” When petitioner voluntarily conveyed numerical information to the phone company and “exposed” that information to its equipment in the normal course of business, he assumed the risk that the company would reveal the information

Page 442 U. S. 736

to the police, cf. United States v. Miller, 425 U. S. 435. Pp. 442 U. S. 741-746.

283 Md. 156, 389 A.2d 858, affirmed.

BLACKMUN, J., delivered the opinion of the Court, in which BURGER, C.J., and WHITE, REHNQUIST, and STEVENS, JJ., joined. STEWART, J., post, p. 442 U. S. 746, and MARSHALL, J., post, p. 442 U. S. 748, filed dissenting opinions, in which BRENNAN, J., joined. POWELL, J., took no part in the consideration or decision of the case.

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