Police Can’t Force You to Unlock Your Phone with Finger or Face, Judge Rules

{Also posted at cyber.pabar.org}

On January 10, 2019, a federal magistrate judge limited law enforcement’s requests to utilize biometric features, e.g., finger, facial or iris recognition, to unlock smartphones or computers that may be found at a residence during a search. The ruling came In the Matter of the Search of a Residence in Oakland, California, Case No. 4-19-70053, in the United States District Court for the Northern District of California by U.S. Magistrate Judge Kandis A. Westmore.

What the Government Wanted

The government was investigating two individuals for extortion of a third person. The alleged perpetrators were accused of using Facebook Messenger for communications threatening to release an embarrassing video of the victim unless the victim paid money. The government agents applied for a search warrant supported by an affidavit seeking to:

  1. Search a specified residence in Oakland, California.
  2. Seize any mobile telephones, computers or similar devices during the search.
  3. Compel any person present to press a finger, thumb or utilize other biometric feature such as facial or iris recognition to unlock the digital devices found in order to permit a search of the contents of the device.

Fourth Amendment Limits the Government

While Judge Westmore found probable cause existed to search the residence, she further found the request overbroad and therefore in violation of the Fourth Amendment of the United States Constitution, because the request was to seize and search the electronic devices of anyone present and was not limited to the identified suspects and their devices. The judge invited the agents to reapply for a warrant limited to those devices reasonably believed by law enforcement to be owned and controlled by the two suspects identified in the affidavit.

Fifth Amendment Further Limits the Government

Judge Westmore went on to determine that forcing suspects to supply a finger, thumb or other biometric feature to unlock a device would violate the Fifth Amendment, which forbids the government from requiring any person to incriminate himself or herself. She noted that previous courts have held that a numeric or alphanumeric passcode cannot be compelled under the Fifth Amendment, because the act of communicating the passcode is testimonial.

The decision also addressed whether the use of a suspect’s biometric feature to potentially unlock an electronic device is testimonial under the Fifth Amendment. Judge Westmore wrote, “[t]he challenge facing the courts is that technology is outpacing the law.” Further, “[c]ourts have an obligation to safeguard constitutional rights and cannot permit those rights to be diminished merely due to the advancement of technology; …. 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.’” She cited Carpenter v. United States, 138 S. Ct. 2206, 2214, 201 L. Ed. 2d 507 (2018).

She found in this context, biometric features serve the same purpose as a passcode, which is to secure the owner’s content, pragmatically rendering the biometric feature and passcode functionally equivalent. She reasoned that use of a finger, thumb or other biometric feature to unlock a device would similarly be testimonial because such an act concedes that the device was in the possession and control of the suspect, and authenticates ownership or access to the device and its contents. She finds that the biometric feature is analogous to the nonverbal, physiological responses elicited during a polygraph test, which are used to determine guilt or innocence, and are considered testimonial. She distinguished this from routine non-testimonial physical acts found not to be protected by the Fifth Amendment, such as providing a blood sample, fingerprinting, handwriting sample or standing in a lineup.


The magistrate judge’s decision could be overturned on appeal, as happened in Illinois in 2017 with a similar ruling. This will be an interesting case to monitor.

Final Thoughts

For anyone concerned about government intrusion into their smartphone, I recommend having a strong alphanumeric passcode.


Jeffrey A. Franklin heads the Cyber Law group at Prince Law Offices P.C. He is also the president and Technology Committee Chair of the Berks County Bar Association and principal technology consultant with BrightLine Tech Solutions LLC.

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