Smith v. Maryland
The Supreme Court ruled that police did not need a warrant to have the phone company record the numbers dialed from a robbery suspect's home phone, because people have no reasonable expectation of privacy in the numbers they dial.
The decision established that information voluntarily given to a business like a phone company -- even routine dialing information -- can be handed over to police without triggering Fourth Amendment protection, a rule that would later shape decades of debate over government access to phone and business records.
How it got here: A Maryland trial court denied the suspect's motion to suppress the pen register evidence and convicted him; Maryland's highest court affirmed, and he asked the Supreme Court to review that ruling.
The Case in Depth
What happened
After a Baltimore woman was robbed, she began getting threatening calls from a man claiming to be the robber. Police identified a suspect, Michael Lee Smith, from a car matching the robber's description. Without a warrant, they had the phone company install a device recording numbers dialed from Smith's home phone, which showed a call to the victim. That evidence helped police get a warrant to search his home and led to his robbery conviction.
The question before the Court
When police had the phone company record the numbers a robbery suspect dialed from his home phone, without a warrant, did that count as a Fourth Amendment search?
Why it matters
The ruling meant that police could obtain records of who a person called, without a warrant, by simply asking the phone company. It became a foundational precedent for the idea that records held by third-party businesses -- banks, phone companies, and later internet and cellphone providers -- get less constitutional protection than the contents of communications themselves.
What changes now
The conviction stands, and the pen register evidence remains admissible. The ruling became a lasting precedent governing how police can obtain phone and other business records without a warrant, later cited in disputes over bank records, email metadata, and cellphone location data as courts wrestled with how far the third-party rule extends into digital-age surveillance.
What this does not decide
The Court's ruling is limited to the numbers dialed, not the content of calls -- a wiretap capturing conversation still requires a warrant under Katz. The opinion also does not address a non-household member's ability to challenge pen register surveillance of someone else's phone, which the Court noted was a distinct question.
Concurrences and dissents
Dissent — Justice Stewart
Justice Stewart argued that numbers dialed from a private telephone deserve the same Fourth Amendment protection as the conversation itself, because both are integral parts of a phone call made from a constitutionally protected space. He rejected the idea that the phone company's ability to record numbers for billing purposes should strip away privacy protection, noting the same logic could apply to conversations too.
Dissent — Justice Marshall
“It is idle to speak of "assuming" risks in contexts where, as a practical mater, individuals have no realistic alternative.”Marshall's objection to the majority's reasoning that dialing a number means accepting the risk of disclosure.
Justice Marshall attacked the majority's 'assumption of risk' reasoning, arguing that people have no real choice but to use the phone system and so cannot meaningfully be said to accept the risk of government surveillance. He warned that letting the government define privacy expectations by simply announcing surveillance practices would let the government erode Fourth Amendment protections at will, and stressed the chilling effect on political and journalistic activity.
How the Court got there
The legal reasoning, step by step
- The Court applied the two-part test from Katz v. United States: whether a person actually expected privacy, and whether that expectation is one society recognizes as reasonable.
- The Court reasoned that phone users generally know they must convey the numbers they dial to the phone company's switching equipment to complete a call, and that phone companies keep records of dialed numbers for billing, fraud detection, and other business purposes.
- Because people are aware the phone company can and does record dialed numbers, the Court concluded that people in general do not actually expect the numbers they dial to remain secret.
- Even if the suspect personally expected privacy, the Court held that expectation was not one society would recognize as reasonable, because he had voluntarily turned the numbers over to a third party -- the phone company -- in the ordinary course of using its service.
- Relying on its earlier ruling that bank customers have no reasonable expectation of privacy in records voluntarily given to banks, the Court extended the same voluntary-disclosure, third-party rule to phone numbers dialed and recorded by phone companies.
- The Court concluded that because installing the recording device did not invade any reasonable expectation of privacy, it was not a 'search' under the Fourth Amendment at all, so no warrant was ever required.
Doctrinal impact
Cases affected by this decision
Reaffirms Katz v. United States (389 U.S. 347)
The Court relies on Katz's two-part privacy test as the governing framework for deciding what counts as a search.
Reaffirms United States v. Miller (425 U.S. 435)
The Court extends Miller's rule that voluntarily disclosed bank records lack privacy protection to phone numbers given to phone companies.