WASHINGTON  The Supreme Court agreed on Monday to decide whether a police department violated the constitutional privacy rights of an employee when it inspected personal text messages sent and received on a government pager.

The case opens “a new frontier in Fourth Amendment jurisprudence,” according to a three-judge panel of an appeals court that ruled in favor of the employee, a police sergeant on the Ontario, Calif., SWAT team.

Orin S. Kerr, an authority on the Fourth Amendment at George Washington University’s law school, said the case was simultaneously significant and idiosyncratic. “This is the first case on Fourth Amendment protection in data networks,” Mr. Kerr said. But the case arose from unusual circumstances, making it fairly likely that the eventual Supreme Court ruling will be narrow.

The Supreme Court has given public employers wide latitude to search their employees’ offices and files. But it has also said that the Fourth Amendment, which forbids unreasonable government searches, has a role to play in any analysis of that latitude.