Supreme Court Protects Cellphone User Privacy, Prohibits Police From Obtaining GPS Records Without Warrant

Privacy proponents won a huge victory this morning. A ruling by the U.S. Supreme Court bans police from tracking a person using cellphone records unless granted permission from a judge.

NBC News is reporting the 5-4 decision requires a search warrant when any police department nationwide wants to get telephone company tracking data on a specific person. With nearly 95 percent of the U.S. population owning a cellphone, this decision has a widespread impact.

When a person uses a cellphone for either calls or texts, a signal bounces off the nearest antenna tower. If the person is moving while using the phone, the signal is handed off to subsequent towers. Wireless companies keep track of this information for billing purposes.

Police departments eventually figured out that this data can be used to map out where someone has been over a period of time. Today's Supreme Court ruling declared this information mining technique violates the Fourth Amendment to the Constitution.

The court's ruling stems from a case brought by a man named Timothy Carpenter. In 2011, Carpenter was accused and ultimately convicted of robbing multiple Radio Shack and T-Mobile stores. Law enforcement, including the FBI, used months of cellphone data to determine Carpenter was near each store at roughly the same time the crimes were committed.

In court, attorneys for Carpenter argued the data was obtained illegally as a search warrant was not issued. Initially, Carpenter's team lost the argument. Using a Supreme Court decision from decades ago, lower courts determined phone customers do not have a reasonable expectation of privacy, and the data could be used as evidence.

Carpenter rebutted the lower courts' ruling by arguing the old Supreme Court decision did not account for new technology. Since landline telephones did not move, customers did not expect numbers called to be necessarily private. However, with moving phones, companies and police can discover much more about a person than just phone numbers.

Carpenter v. United States made it to the U.S. Supreme Court late last year. Reviewing the case, the justices found cellphone location data contains sensitive information and should be protected.

"The government's position fails to contend with the seismic shifts in digital technology that made possible the tracking of not only Carpenter's location but also everyone else's, not for a short period but for years and years," wrote Chief Justice John Roberts, as cited by CNET.

The court's position does not apply to security cameras, business records, or real-time tracking. The ruing also makes an exception by allowing police to get GPS information without a warrant in cases of emergency such as pursuing a fleeing suspect or protecting someone from imminent harm.