Why your iPhone-unlocking fingerprint is susceptible to FBI search warrants

A judge is forcing a woman to unlock an iPhone with her fingerprints, but does this violate the Constitution?

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Should you be able to plead the Fifth when a judge forces you to use your fingerprints to unlock an iPhone?

That’s the latest ongoing debate in a Los Angeles courtroom after a judge compelled a woman in custody to use Touch ID to unlock an iPhone. Legal experts are arguing that this goes against the Fifth Amendment’s protection against self-incrimination because the authorities would then have access to potentially-incriminating personal data stored on the device.

The debate started after authorities obtained a search warrant for Paytsar Bkhchadzhyan, the girlfriend of a suspected Armenian gang member, to use her fingerprints to unlock an iPhone seized from a home in Glendale, California. The iPhone in question was enabled with Touch ID sensor technology.

In February, Bkhchadzhyan was sentenced to a felony count of identify theft. According to court documents, it only took 45 minutes after Bkhchadzhyan was taken into custody for U.S. Magistrate Judge Alicia Rosenberg to order her to press her fingerprints on the iPhone. Bkhchadzhyan’s fingerprints were collected by an FBI agent that same day.

Even though the U.S. Supreme Court has ruled that authorities can obtain a search warrant for mobile phones and can force people in custody to hand over physical evidence including fingerprints without a judge order, legal experts say this case is different. Their argument is that forcing a person to use their fingerprints to unlock an iPhone could be a form of self-incrimination, in violation of the Fifth Amendment.

According to Susan Brenner, a law professor at the University of Dayton, this is on par with unlawfully forcing someone to testify incriminating testimony. By unlocking the iPhone with her fingerprints, Bkhchadzhyan would be authenticating the data on the phone and become associated with it.

“By showing you opened the phone, you showed that you have control over it,” Brenner told the LA Times. “It’s the same as if she went home and pulled out paper documents—she’s produced it.”

But not every legal expert believes that fingerprints fall under the Fifth Amendment’s protection against self-incrimination. In fact, Touch ID may be a legal loophole to forcing someone to reveal their passcode.

“Unlike disclosing passcodes, you are not compelled to speak or say what’s ‘in your mind’ to law enforcement,” Albert Gidari, the director of privacy at Stanford Law School’s Center for Internet and Society, told the LA Times. “‘Put your finger here’ is not testimonial or self-incriminating.”

Why this matters: The issue boils down to the earlier ruling that fingerprints are “physical evidence,” like a key. The legal system does not require a search warrant for physical evidence. However, producing an iPhone passcode is considered knowledge stored in one’s mind, so forcing someone to disclose the passcode is protected under the Fifth Amendment. 

It gets murky, however, with fingerprint sensors that unlock mobile phones. For Touch ID to be able to unlock an iPhone, a person has to physically press down on the device. A fingerprint scan won’t do. So it’s more involved than just handing over a key. It’s forcing someone to perform an action with a key only they can use.

This story, "Why your iPhone-unlocking fingerprint is susceptible to FBI search warrants" was originally published by Macworld.