Smith v. Maryland

Background

A Baltimore woman was robbed and then received threatening phone calls. Police traced the car to Michael Lee Smith and asked the telephone company to install a pen register at its central office to record numbers dialed from Smith’s home. The pen register showed a call from Smith’s number to the victim. Police then got a search warrant, searched Smith’s house, and used that evidence at trial. Smith challenged the pen register because no warrant was obtained before it was installed.

Reasoning

The Court applied the familiar test about whether someone has a reasonable expectation of privacy. It stressed that pen registers record only the numbers dialed, not the content of calls. The majority said people voluntarily convey numbers to the phone company and know the company can and does record numbers for billing and other business reasons. Because dialed numbers are exposed to a third party, the Court concluded there was no legitimate expectation of privacy in those numbers and thus no Fourth Amendment “search.” The state courts’ rulings were affirmed.

Real world impact

As a practical matter, the decision permits police to get dialing records via pen registers without first getting a warrant, making it easier to trace who called whom. Telephone subscribers’ dialing patterns can be collected and used as evidence in investigations without the heightened protection of a warrant.

Dissents or concurrances

Two Justices dissented, arguing that numbers dialed from a private home can reveal intimate associations and should be protected like the content of calls, and that warrants or judicial review should be required before government access.