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In a victory for privacy advocates, a federal appeals court in Florida ruled that law enforcement agents cannot force mobile carriers to turn over the location history of their customers without a search warrant.

The case involved an appeal by Quartavius Davis, who was convicted by a jury for his role in a violent armed robbery spree targeting restaurants and gas stations. The evidence included location data gleaned from cellphone towers that showed Davis had been in proximity of the various businesses.

In finding that the police should had obtained a warrant to obtain the location data, the 11th Circuit Court of Appeals unanimously ruled that the government violated Davis’ Fourth Amendment right against unreasonable search and seizure.

The case is groundbreaking because higher courts have yet to rule definitively on whether people have a privacy right in the location disclosed by their cell phones. Citing a recent Supreme Court case that suggested police in some cases need a warrant to track a suspect’s automobile, the appeals court noted that a cell phone carries deeper privacy implications:

Even on a person’s first visit to a gynecologist, a psychiatrist, a bookie, or a priest, one may assume that the visit is private if it was not conducted in a public way […] One’s cell phone, unlike an automobile, can accompany its owner anywhere […] There is a reasonable privacy interest in being near the home of a lover, or a dispensary of medication, or a place of worship, or a house of ill repute. (emphasis and ellipsis added)

The court also drew a firm line between what police must do to obtain call records from a phone company, which can share records without a warrant under the so-called “third-party doctrine,” versus what is required to obtain a person’s location.

Declaring that a person’s location is more analogous to the content of a phone call (for which police do need a warrant), the court stated that people can reasonable expect that their mobile carrier will not hand over a historic record of the places they have been.

In finding a privacy right in cellphone location, the court also gave full-throated support to a modern interpretation of the Fourth Amendment. That interpretation finds that the right against unreasonable searches doesn’t apply only in cases of physical trespass — such as when police break down a door — but to more general notions of privacy too.

Finally, the case also highlights the ability of cellphone towers to observe and record a phone user’s location. While the court acknowledged that the tower’s do not disclose a person’s precise location, it ruled that they reveal enough information to trigger the Fourth Amendment’s privacy protection.

While the ruling is a major victory for civil libertarians, it is not good news for Davis, the defendant. The court ruled that, under a legal exception, the evidence did not have to be excluded — meaning Davis will still remain in prison the rest of his life.

Here is the ruling with relevant parts underlined. It is so far the most important privacy decision this year:

11th Circuit Phone Search

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