Cops can force suspect to unlock phone with thumbprint, US court rules

US District Courts applying Doe and Hubbell have reached different conclusions on biometric unlocking. The 9th Circuit decided that the compelled use of Payne's thumb "required no cognitive exertion" because it "merely provided CHP with access to a source of potential information, much like the consent directive in Doe. The considerations regarding existence, control, and authentication that were present in Hubbell are absent or, at a minimum, significantly less compelling in this case. Accordingly, under the current binding Supreme Court framework, the use of Payne's thumb to unlock his phone was not a testimonial act and the Fifth Amendment does not apply."

The 9th Circuit panel said its "opinion should not be read to extend to all instances where a biometric is used to unlock an electronic device," as "Fifth Amendment questions like this one are highly fact dependent and the line between what is testimonial and what is not is particularly fine."

"Indeed, the outcome on the testimonial prong may have been different had Officer Coddington required Payne to independently select the finger that he placed on the phone," the ruling said. "And if that were the case, we may have had to grapple with the so-called foregone conclusion doctrine. We mention these possibilities not to opine on the right result in those future cases, but only to demonstrate the complex nature of the inquiry."

Foregone conclusion doctrine

The foregone conclusion doctrine noted above generally "applies if the government can show it knows the location, existence, and authenticity of the purported evidence with reasonable particularity," according to the National Association of Criminal Defense Lawyers.

"Even if the act of decryption is potentially testimonial, it may not violate the Fifth Amendment if the implicit facts conveyed by doing so would be a 'foregone conclusion' that 'adds little or nothing to the sum total of the government's information,'" the lawyers' group explains in a primer on compelled decryption.

Yesterday's ruling from the 9th Circuit also rejected Payne's argument that California Highway Patrol violated his Fourth Amendment rights. The Fourth Amendment dispute involved a special search condition in Payne's parole "requiring him to surrender any electronic device and provide a pass key or code, but not requiring him to provide a biometric identifier to unlock the device," the ruling said.

Despite that parole condition, "the search was authorized under a general search condition, mandated by California law, allowing the suspicionless search of any property under Payne's control," the ruling said.
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"Moreover, we hold that any ambiguity created by the inclusion of the special condition, when factored into the totality of the circumstances, did not increase Payne's expectation of privacy in his cell phone to render the search unreasonable under the Fourth Amendment," the panel wrote.