The Fourth Amendment prohibits police from conducting warrantless searches and seizures. Over the past century or so, courts have found that police may conduct a search or seize property without a warrant under certain circumstances, provided that they have probable cause to believe that they will find evidence directly related to criminal activity. Technological advances have also required ongoing challenges to the Fourth Amendment’s warrant requirement. The use of digital tracking evidence has recently posed many challenges for defendants, prosecutors, and courts. The U.S. Supreme Court heard oral arguments in late 2017 in a case challenging the use of cell phone location data by police without a warrant. The court is likely to issue a decision in Carpenter v. United States in the summer of 2018, which may affect Texas criminal cases moving forward.
An individual must have a “reasonable expectation of privacy” for the Fourth Amendment’s warrant requirement to apply. See Katz v. United States, 389 U.S. 347 (1967). When an individual voluntarily discloses information to a third party, courts have generally held that they no longer have a reasonable expectation of privacy in that information. This is known as the “third-party doctrine.” For example, the Supreme Court held that the warrantless use of a pen register to record the phone numbers dialed from a telephone was not a “search” under the Fourth Amendment, since the telephone company would receive and keep records of those numbers. Smith v. Maryland, 442 U.S. 735 (1979).
The Carpenter case questions whether certain uses of telecommunications technology involve a genuinely voluntary disclosure. In Smith, the court treated dialing a telephone number as the voluntary disclosure of information. Almost any sort of electronic communication, however, requires “disclosing” information to the telecommunications provider. This raises questions about how voluntary such a disclosure could be. The only alternative would be to limit all communications to in-person conversation, which is not exactly practical in the 21st century.