The United States Court of Appeals for the Sixth Circuit ruled Tuesday that police can use cell phone data obtained without a warrant to establish an individual’s location.

The case, United States v. Skinner, involved a suspected drug trafficker, Melvin Skinner, who was tracked and arrested by the Drug Enforcement Administration (DEA).

“The drug runners in this case used pay-as-you-go (and thus presumably more difficult to trace) cell phones to communicate during the cross country shipment of drugs,” Judge John Rogers wrote in his opinion (PDF). “Unfortunately for the drug runners, the phones were trackable in a way they may not have suspected. The Constitution, however, does not protect their erroneous expectations regarding the undetectability of their modern tools.”

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The U.S. Supreme Court ruled in January that police could not plant a GPS tracking device on a suspect’s car without obtaining a warrant. However, Rogers ruled that the Fourth Amendment did not prevent law enforcement agencies from tracking a cell phone’s location.

“Skinner did not have a reasonable expectation of privacy in the data emanating from his cell phone that showed its location,” Rogers wrote. “Skinner himself obtained the cell phone for the purpose of communication, and that phone included the GPS technology used to track the phone’s whereabouts.”

“Law enforcement tactics must be allowed to advance with technological changes, in order to prevent criminals from circumventing the justice system,” he added.

Cell phones continuously transmit data to cell-sites scattered across the nation. The cell-sites are operated by cell phone service providers, who keep records of the cell phone’s geolocational data.

Law enforcement agencies can obtain cell phone records from service providers, giving them access to the phone’s locational data. In addition, computers scientists have found it is relatively easy and inexpensive to set up a device to track a cell phone’s position, without any collaboration with cell phone service providers.

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According to an investigation by the American Civil Liberties Union, cell phone tracking by police is widespread. While some police departments obtain a warrant to track cell phones, many do not.

[Cell phone location data via Shutterstock]