Want to keep your phone secure from the government? Better use a password and not a fingerprint.

Just two weeks ago, the United States District Court for the District of Columbia (2018 WL 3155596) ruled that the government can force you to provide your fingerprints (and other biometric features) for the purpose of unlocking your phone.

This is not the first court to reach this conclusion. The Minnesota Supreme Court (Minnesota v. Diamond, 905 N.W.2d 870 (Minn. 2018)), a Florida appellate court (Florida v. Stahl, 206 So. 3d 124 (Fla. 2016)), a Virginia trial court (Virginia v. Baust, 89 Va. Cir. 267 (Va. Cir. Ct. 2014)), and an Illinois federal court (In re Search Warrant Application, 279 F. Supp. 3d 800 (N.D. Ill. 2017)) all reached the same outcome.

The rationale behind these decisions is simple. Under the Fifth Amendment, the government cannot force you to make a “testimonial” statement.

The United States Supreme Court has repeatedly held that physical acts are not testimonial. So the government can force you to do all kinds of physical things. It can force you to provide a voice sample (United States v. Wade, 388 U.S. 218 (1967)), a handwriting sample (Gilbert v. California, 388 U.S. 263 (1967)), and a blood sample (Schmerber v. California, 384 U.S. 757 (1966)).

Fingerprints are no different. Pre-iPhones, at least two federal appellate decisions (United States v. Hook, 471 F.3d 766 (7th 2006) and Williams v. Schario, 93 F.3d 527 (8th Cir. 1996) (per curiam)) concluded that fingerprints are not protected by the Fifth Amendment. And dicta in a United States Supreme Court dissent (Doe v. United States, 487 U.S. 201 (1988) (Stevens, J., dissenting)) took the position that that fingerprints fall in the same category as blood, voice, and handwriting samples.

Yet with modern cell phones and their various uses and capabilities, fingerprints can be used to unlock phones and discover a vast amount of information. Though that fact seems not to have swayed the courts cited above. Despite all the private information the government can access with a mere swipe of a finger, it does not change the fact that this is just compelling a physical act.

But this is not the only conclusion.

A different Illinois federal court (In re Application for a Search Warrant, 236 F. Supp. 3d 1066 (N.D. Ill. 2017)) held that forced fingerprinting (for the purpose of unlocking cellphones) is testimonial. The court’s rationale was two-fold.

One: the fingerprint links the person to the cellphone. If the fingerprint unlocks the phone, this is tantamount to testimony that he or she controls the device.

This is a fair point.

But you could make the same point about providing a blood sample. If the blood sample matches other DNA evidence, it is tantamount to testimony that the person was at the scene of the crime. So, if the government can do this with blood samples, why should the government not be able to do it with fingerprints?

The answer: Riley v. California, 134 S. Ct. 2473 (2014) (the court’s second rationale). Riley is a United States Supreme Court decision on when warrants are required to search cellphones. Generally always, said Riley. In the course of reaching that answer, Riley recognizes the game changing nature of cellphones—we carry intimate information in vast amounts at all times. That resulted in changing the rules for the Fourth Amendment. And the Illinois federal court in In re Application for a Search Warrant believed the same should happen with the Fifth Amendment.