Facts
- After a Baltimore robbery, the victim received threatening calls; the caller directed her to her porch, where she saw a car she associated with the robber.
- Police traced the car’s license plate to Michael Lee Smith.
- Without a warrant, police asked the telephone company to install a pen register at its central office to record numbers dialed from Smith’s home phone.
- The pen register recorded a call from Smith’s phone to the victim’s number.
- Using that information, police obtained a search warrant for Smith’s home and found items including a phone book opened or marked to the victim’s listing.
- Smith was arrested, identified in a lineup, and convicted of robbery and related offenses after his motion to suppress evidence derived from the pen register was denied.
Issues
- Whether installing and using a pen register, without a warrant, to record numbers dialed from a suspect’s home telephone is a “search” under the Fourth Amendment.
- Whether a caller has a legitimate expectation of privacy in the numbers dialed and conveyed to the telephone company for routing and billing.
Decision
- The Supreme Court affirmed the conviction.
- The Court held that installation and use of a pen register to record dialed numbers was not a Fourth Amendment search and therefore did not require a warrant.
- Applying the reasonable-expectation-of-privacy test, the Court concluded that callers generally know dialed numbers are conveyed to and recorded by the phone company for business purposes.
- The Court reasoned that, by voluntarily conveying dialed numbers to the phone company, Smith assumed the risk that the company would disclose that information to police.
- The Court emphasized that a pen register records only dialing information and not the contents of communications.
Legal Principles
- Fourth Amendment protection turns on whether the defendant had a subjective expectation of privacy that society recognizes as reasonable.
- Information voluntarily conveyed to a third party in the ordinary course of business is generally not subject to a reasonable expectation of privacy when obtained from or through that third party.
- Pen registers capture non-content dialing information; obtaining such transactional routing data from a phone company does not, by itself, constitute a Fourth Amendment search.
Conclusion
The Court ruled that police do not conduct a Fourth Amendment search when they use a pen register, without a warrant, to record numbers dialed from a home phone, because the caller exposes those numbers to the telephone company and lacks a legitimate expectation of privacy in that routing information.