Dec 15, 2014 · 2 minutes

A police officer's ignorance of the law, combined with bizarre decisions concerning when law enforcement can access a smartphone, could be a disaster for privacy in the United States.

The first part of that equation comes from the Supreme Court's decision that a police officer collecting information via a traffic stop based on a misunderstanding of the law, such as when a car can be stopped for malfunctioning brake lights, doesn't violate the Fourth Amendment. (The case was brought to the Supreme Court after a cop found a sandwich bag full of cocaine in the trunk of someone's car after pulling him over because one of his brake lights was out.)

That's a problem. In a dissenting opinion, Justice Sonia Sotomayor wrote that the Supreme Court's decision "means further eroding the Fourth Amendment’s protection of civil liberties in a context where that protection has already been worn down." She also argued that it's hard to figure out "how a citizen seeking to be law-abiding and to structure his or her behavior to avoid these invasive, frightening and humiliating encounters could do so" after the ruling.

An officer's ability to stop anyone he likes, only to later claim he misunderstood the law he cited to do so, is problematic for several reasons. Prime among them is the unclear laws regarding when those officers can request access to a citizen's smartphone. The Supreme Court believes doing so requires a warrant; other judges have argued that police can require someone to unlock a device that uses a biometric security system instead of a passcode.

As I reported when a Circuit Court judge issued that opinion in October:

Need another reason not to secure your smartphone with a fingerprint? A Circuit Court judge has ruled that police can require suspects to unlock a device with their fingerprint, but may not with a passcode. When it comes to keeping information away from the police, at least, it may be better to rely on four numerical digits than just one physical one.

The judge’s decision was based on the idea that “giving police a fingerprint is akin to providing a DNA or handwriting sample or an actual key, which the law permits,” the Virginian-Pilot says in its report on the decision. This doesn’t mean that a suspect’s phone can be accessed with just a fingerprint — some software requires an additional passcode to be opened — but it does mean that an iPhone could be laid bare to law enforcement if its owner relies on its TouchID feature alone. Which means that a cop can pull someone over because of his own misunderstanding of the law, require them to unlock their iPhone because they rely on its biometric sensor for security, and use any evidence they find even though the original stop had no basis in any actual law. Or they could steal private photos from those devices and share them with their friends, like one California police officer did to numerous women over the last year, as I reported in November.

All of which means the Supreme Court has made it easier to undermine a ruling they made that actually made sense for people living in the smartphone era. It just takes a little ignorance, willful or otherwise, and a rogue Circuit Court judge to undermine our privacy.

[illustration by Brad Jonas for Pando]