Last month, District Judge Edmond Chang handed down a decision that held that the government, with a search warrant, can require individuals to use their fingerprints to unlock a phone using biometrics without violating the Fifth Amendment. Judge Chang’s decision follows a 2014 Virginia state circuit court decision, which also allowed the government to compel an individual to unlock his phone with his fingerprint.

As biometric security continues to be implemented in our cellphones, these types of questions will confront courts with increasing regularity. For those courts that take the tack of Judge Chang, one issue to consider is whether his approach to fingerprints would apply to newer forms of biometric security—specifically face scans and voice commands. Any possible answer must begin with an understanding of the Fifth Amendment.

The Fifth Amendment states that “[n]o person . . . shall be compelled in any criminal case to be a witness against himself . . . .” To receive Fifth Amendment protection, a person’s statement or act must (i) be compelled; (ii) be testimonial; and (iii) incriminate the person in a criminal proceeding. Certain exceptions aside, the Fifth Amendment protects only compelled communications. Thus, the Fifth Amendment protects a person against incrimination when his compelled communication is testimonial.

So what is considered testimonial? In Doe v. United States, the Supreme Court held that a testimonial “communication must itself, explicitly or implicitly, relate a factual assertion or disclose information” that expresses “the contents of an individual’s mind.” Because of the Supreme Court’s distinction between testimonial and nontestimonial communication, the government has a lot of freedom in conducting investigations. The government can compel an individual to furnish a handwriting sample, give a blood sample, or try on clothes. None of these examples violates the Fifth Amendment’s right against self-incrimination. Therefore, while the government can compel you to unlock your phone with a fingerprint, it may not be able to compel you to hand over your phone’s passcode.

Now, returning to the question about whether the government can compel you to unlock your phone by either a face scan or by your voice, given Supreme Court precedent, the answer may be yes in both scenarios. The phone’s actual scanning of your face, while compelled, may not be considered testimonial because it is arguably not a communication that explicitly, or implicitly, relates a factual assertion or a disclosure of information. The face scan is no different than the fingerprint—it simply unlocks your phone.

Similarly, if the voice-command to unlock your phone is “Ok, phone,” then what is being compelled may be considered identification—having your phone recognize your voice and unlock— rather than testimonial or communicative content, thereby falling into the same category as a fingerprint. Now, on the other hand, if the government were to compel you to unlock your phone by a voice command that revealed your password, that would seem more clearly a violation of your Fifth Amendment right against self-incrimination because your communication—the voice password—is explicitly disclosing information.

Of course, Congress can change all of this with a legislative fix. Justice Roberts noted in Riley v. California that modern cell phones, with all they contain and may reveal, hold “for many Americans ‘the privacies of life.’” And increased biometric security in cellphones will help protect those privacies. But given current case law, while we are protecting our cellphones from thieves and hackers with biometric security, we are opening a direct door for the government. Another example of the law of unintended consequences….