A California judge has refused to allow law enforcement to use a “finger, thumb, iris, or other biometric feature” to unlock digital devices of any individual present at an investigation, a decision that could impact how courts weigh biometric privacy rights going forward,

In a Jan. 10 order, U.S. Magistrate Judge Kandis Westmore of the Northern District of California wrote the federal government was out of bounds with the Fourth and Fifth Amendments in attempting “to compel any individual present” during a search “to press a finger (including a thumb) or utilize other biometric features” to unlock digital devices for authorized search.

In the order, Westmore explained that biometrics should be granted the same constitutional protections as passwords, noting that courts have previously “found that a passcode cannot be compelled under the Fifth Amendment, because the act of communicating the passcode is testimonial.”

“Courts have an obligation to safeguard constitutional rights and cannot permit those rights to be diminished merely due to the advancement of technology,” she wrote, citing Carpenter v. United States, an influential U.S. Supreme Court decision tackling how the Fourth Amendment should be applied to technological developments. ”Citizens do not contemplate waiving their civil rights when using new technology, and the Supreme Court has concluded that, to find otherwise, would leave individuals 'at the mercy of advancing technology.' ”

But should people expect judges to view things similarly down the road? Brett Max Kaufman, an American Civil Liberty Union attorney who worked on the Carpenter arguments that his organization brought before SCOTUS, said “we're going to start seeing more of these for sure.”

“I think we're about at the moment now where we're a few years past the widespread introduction and adoption of biometrics to protect phones, and we've seen a smattering of cases involving [biometrics] most of which went through the other way [from Westmore's decision] over the years,” he said. “I think we're going to see a lot more judges take on this analysis.”

The order stems from a government investigation into two individuals who allegedly threatened a victim via Facebook Messenger to distribute “an embarrassing video of him” unless he paid. The government applied for a warrant to search and seize items from an Oakland residence connected to the individuals under investigation, including mobile phones and computer, as well as require anyone at the residence to try and unlock devices with biometric means.

The case is under seal other than Westmore's order, and the DOJ attorney listed on the docket, Assistant U.S. Attorney Robert Leach, didn't respond to an email seeking comment.

However, Westmore wrote that the government's argument likens biometric unlocking to “submitting to fingerprinting or a DNA swab,” both of which aren't considered testimonial. The judge however disagreed, reasoning fingerprinting is to “merely compare [a suspect's] fingerprints” to others found on the crime scene, whereas “a successful finger or thumb scan confirms ownership or control of the device, and, unlike fingerprints, the authentication of its contents cannot be reasonably refuted.”

The government seems “to see biometrics as sort of a lifeline on something that they were not constitutionally permitted to do,” Kaufman said. “Their argument is, 'We can take fingerprints, so why can't we just use your fingerprints?' And I think what [Westmore's] opinion does—which is an argument that is going to be persuasive to a lot of judges—is that you can't just blindly apply those. You need to look at why they're doing it. Especially in the context of the technology. I think the public sees these biometrics features as additional security and privacy, and the government is turning them into loopholes for privacy and security.”

Indeed, biometrics technology may be getting more popular. A 2017 Visa survey of Americans pegged the number of those interested in using biometrics for authorizing payments at 86 percent, while a University of Texas survey finds that 58 percent of survey participants were “very comfortable with fingerprint scanning.”

Further, the situation Westmore presided over isn't unprecedented. A U.S. Magistrate Judge in the Northern District of Illinois in 2017, whose order Westmore cited, used the Fourth and Fifth Amendments to deny a warrant to compel individuals present at the scene of an investigation to use their “fingerprints and/or thumbprints” to unlock Apple devices.

“I think that what will happen is there will be other judges that get similar applications” for a warrant as those Westmore considered, said Brian Owsley, assistant professor of law at the University of North Texas at Dallas College of Law, and a former magistrate judge. “In my experience what happens is this is driven oftentimes from Main Justice—the U.S. attorneys and their investigative agents are filing requests around the country, and they'll maybe start adding biometrics language.”

“The next time, maybe a judge in the Middle District of Florida gets something like this, she might say, 'Oh, no, this is like what Westmore did. And that gave me pause, and I agree with her reasoning and stuff like that, and I'm going to issue an order denying [the warrant].”