A United States judge has ruled that forcibly unlocking smartphones secured by biometrics is a violation of the Fifth Amendment.

Judge Kandis Westmore, a U.S. District Court judge for the Northern District of California recently denied a request from law enforcement to issue a search warrant allowing a mobile device to be unlocked using iris scan, facial recognition or fingerprint. According to reports, the ruling said that forcibly unlocking devices with biometric data would be the equivalent of testifying against oneself, which is a violation of the Fifth Amendment. The decision adds biometric sensor data to the list of login information, including personal identification numbers (PINs) and passwords, already covered under Fifth Amendment safeguards against self-incrimination.

The judge wrote: "If a person cannot be compelled to provide a passcode because it is a testimonial communication, a person cannot be compelled to provide one’s finger, thumb, iris, face, or other biometric feature to unlock that same device. The undersigned finds that a biometric feature is analogous to the 20 nonverbal, physiological responses elicited during a polygraph test, which are used to determine guilt or innocence, and are considered testimonial."

However, a higher court could still overturn Westmore’s decision, which was made at the district level.

This news follows recent headlines that law enforcement has used the fingerprints of dead people to unlock their devices. Researchers have also recently made headlines for being able to 3D print synthetic fingerprints and dummy heads for the purpose of unlocking devices.