On June 11, 2014, the 11th U.S. Circuit Court of Appeals held that police will need a search warrant to obtain the metadata that allows a phone carrier to determine your location.

What location metadata are we talking about?
The metadata in question here is the cellphone’s location. In addition to the GPS capabilities of most modern phones, all phones constantly broadcast location metadata to their cellphone providers. In order to remain connected to the cell network, your cellphone constantly pings nearby cell towers, so that the phone company will know which tower to route incoming calls and data through. If your phone is pinging a specific tower, then obviously you must be close enough to that tower to be able to connect to it. When there’s more than one tower in an area, the phone company is able to triangulate a more exact position. Given enough towers, the phone company is able to determine your exact location at any point in time.
Why didn’t the police need a search warrant to get Quartavious Davis’s location metadata?
Thanks to the Fourth Amendment, police usually need search warrants in order to seize private information, except when that information qualifies under one of several exceptions. For Quartavious Davis, the police tried to argue that the location metadata fell under the Third-Party Doctrine.
The Third-Party Doctrine says that any information you knowingly reveal to a third-party will not receive Fourth Amendment protections against unreasonable searches and seizures. Because that information isn’t protected by the Fourth Amendment, the police will only need a court order instead of a search warrant. The distinction is that it’s much harder for police to get search warrants, which require the police to show a judge that there’s probable cause. A court order requires only reasonable grounds for belief, which they can show by arguing that the information is relevant and material to the investigation.
So what did the 11th Circuit decide?
What the courts are arguing about at this point is whether or not the location metadata is knowingly and voluntarily revealed to your cellphone company or not. The 11th Circuit held that because Davis had not knowingly or voluntarily sent the metadata to his phone company, he had not waived his reasonable expectation of privacy.
This most recent decision only has validity in Florida, Georgia, and Alabama, and directly contradicts a decision from the 5th Circuit earlier last year, which held that merely owning a phone equals consent to constant tracking. Because two different Circuits directly contradict on this issue, it’s likely the U.S. Supreme Court will step in soon to sort this mess out.
My thoughts on the issue
The 11th Circuit decision mostly punted the in-depth analysis which would give some weight to its decision: does mere ignorance shield society from privacy intrusions? Anyone technologically-fluent already understands that their cell phones are constantly broadcasting location metadata, and our society’s understanding of this fact is increasing every day. At some point enough people will understand how their phones work that the courts will feel comfortable throwing out this privacy protection. In another landmark case, Smith v. Maryland from 1979, the U.S. Supreme Court argued that all people must realize that when they dial (landline) phone numbers, those numbers are sent to their telephone companies, and that everyone knows those companies have facilities for permanently storing those records. After all, if you know that someone is constantly monitoring you, do you really have any reasonable expectation of privacy after all? At some point our society will be technologically-fluent enough that the courts will unanimously expect us all to know similar things about our cellphone providers. Hopefully we’ll be able to cobble together enough protections before then.