Smith v. Maryland, 442 U.S. 735 (1979), was a Supreme Court case holding that the installation and use of a pen register by the police to obtain information on a suspect's telephone calls was not a "search" within the meaning of the Fourth Amendment to the United States Constitution, and hence no search warrant was required. In the majority opinion, Justice Harry Blackmun rejected the idea that the installation and use of a pen register constitutes a violation of the suspect's reasonable expectation of privacy since the telephone numbers would be available to and recorded by the phone company anyway.