Smith v. Maryland

Decided June 20, 1979. Harry Andrew Blackmun delivered the opinion of the Court.

Docket 78-5374 · 442 U.S. 735 (1979) · Cited 2,305 times

Holding

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 Court’s statement of the holding, from the opinion’s syllabus. The syllabus is prepared by the Reporter of Decisions and is not part of the opinion of the Court — read the official opinion for authority.

How the Justices voted

Decided 5–3.

“Concurring” means agreeing with the outcome; any split shown is the Court’s judgment, not each Justice’s reasoning. Source: the Supreme Court Database (Spaeth et al.), Washington University.

Precedents cited

Supreme Court decisions this opinion relies on, ordered by how often it cites each. Cases in our collection link through; others are named.

• Katz v. United States · 389 U.S. 347 (1967)
• United States v. White · 401 U.S. 745 (1971)
• United States v. New York Telephone Co. · 434 U.S. 159 (1977)
• Rakas v. Illinois · 439 U.S. 128 (1978)
• United States v. Miller · 425 U.S. 435 (1976)
• California Bankers Assn. v. Shultz · 416 U.S. 21 (1974)
• Branzburg v. Hayes · 408 U.S. 665 (1972)
• Hoffa v. United States · 385 U.S. 293 (1966)
• Lopez v. United States · 373 U.S. 427 (1963)
• United States v. Giordano · 416 U.S. 505 (1974)
• Couch v. United States · 409 U.S. 322 (1973)
• Terry v. Ohio · 392 U.S. 1 (1968)
• Mapp v. Ohio · 367 U.S. 643 (1961)
• National Ass'n for the Advancement of Colored People v. Alabama Ex Rel. Patterson · 357 U.S. 449 (1958)
• United States v. Chadwick · 433 U.S. 1 (1977)
• United States v. United States District Court for the Eastern District of Michigan · 407 U.S. 297 (1972)
• United States v. Dionisio · 410 U.S. 1 (1973)
• Mancusi v. DeForte · 392 U.S. 364 (1968)

Cited by

Later Supreme Court opinions in our collection that cite this case.

• Carpenter v. United States · 585 U.S. 296 (2018)
• Oliver v. United States · 466 U.S. 170 (1984)
• California v. Ciraolo · 476 U.S. 207 (1986)
• United States v. Knotts · 460 U.S. 276 (1983)
• California v. Rooney · 483 U.S. 307 (1987)
• United States v. Jacobsen · 466 U.S. 109 (1984)
• Kyllo v. United States · 533 U.S. 27 (2001)
• United States v. Dunn · 480 U.S. 294 (1987)
• California v. Greenwood · 486 U.S. 35 (1988)
• Bond v. United States · 529 U.S. 334 (2000)
• Hudson v. Palmer · 468 U.S. 517 (1984)
• Texas v. Brown · 460 U.S. 730 (1983)
• Immigration & Naturalization Service v. Chadha · 462 U.S. 919 (1983)
• Segura v. United States · 468 U.S. 796 (1984)
• Minnesota v. Carter · 525 U.S. 83 (1998)
• Samson v. California · 547 U.S. 843 (2006)
• United States v. Karo · 468 U.S. 705 (1984)
• Michigan v. Clifford · 464 U.S. 287 (1984)
• Dow Chemical Co. v. United States Ex Rel. Administrator · 476 U.S. 227 (1986)

Official text

Read the official opinion (U.S. Reports, govinfo.gov)

Explore from here

Harry Andrew Blackmun’s profile · All Supreme Court opinions · The Supreme Court

Source: Supreme Court of the United States, slip opinions (1979). Citation count from the Free Law Project’s CourtListener bulk data. Data last verified 2026-07-03. Informational only; verify against the primary source before relying. Not a consumer report (FCRA).