The Fourth Amendment right of the people “to be secure in their persons, houses, papers, and effects” has been center stage in debates over technology that scarcely could have been imagined at the time it was written. See, e.g., Carpenter v. United States, 138 S. Ct. 2206 (2018); United States v. Jones, 565 U.S. 400 (2012). With less fanfare, however, the Fifth Amendment has emerged as another critical consideration in recent cases focused on the protection of information accessible only through biometric scans (such as fingerprint or facial recognition). In the latest example of this trend, the U.S. District Court for the Northern District of California found that the Fifth Amendment right against self-incrimination prohibited the compelled use of biometric smartphone unlocking features, such as fingerprint, thumbprint, facial, or iris recognition, in In the Matter of the Search of a Residence in Oakland, California, No. 4-19-70053, 2019 WL 176937 (N.D. Cal. Jan. 10, 2019). Cases like this one read the right even more broadly than those dealing with the compelled production of passwords. Practitioners should monitor this ongoing judicial dialogue about how the Fifth Amendment should apply to issues newly arising in the information age.

The Northern District of California’s Fifth Amendment analysis in Oakland

In Oakland, the Government applied for a warrant authorizing investigators to compel any individual present at a residence connected to two extortion suspects to utilize biometric features to unlock digital devices found at the residence. Relying on recent U.S. Supreme Court decisions directly addressing the Fourth Amendment, including Carpenter, U.S. Magistrate Judge Kandis A. Westmore ruled that law enforcement could not force suspects to use biometric features to unlock digital devices because using such a feature would be testimonial for purposes of the Fifth Amendment’s protection against self-incrimination. In addition, Judge Westmore ruled that the “foregone conclusion” exception did not apply. She thus denied the warrant application.

In her analysis of whether using biometric features would be testimonial, Judge Westmore was mindful of the fact that “technology is outpacing the law” in some areas. She noted the U.S. Supreme Court’s direction in Carpenter to take technological advances into account when addressing constitutional issues and noted that courts “have an obligation to safeguard constitutional rights and cannot permit those rights to be diminished merely due to the advancement of technology.” Judge Westmore proceeded to observe that courts have previously found passcodes cannot be compelled under the Fifth Amendment, because the communication of a passcode is a testimonial act that expresses the contents of a person’s mind. In addition, she observed prior precedent holding that “testimony” can encompass acts implying assertions of fact. Judge Westmore found the compelled use of biometric unlocking features to violate the Fifth Amendment under each of these lines of precedent. First, she reasoned that in this context biometric features serve as the functional equivalent of a passcode; both are unlocking tools used to access content stored on a device. Second, Judge Westmore reasoned that unlocking a device concedes the suspect had possession and control of the device and authenticates ownership or access to the device and all of its contents.

Thus, Judge Westmore concluded, unlocking a device using biometric features is unlike non-testimonial but potentially incriminating acts such as furnishing a blood sample or submitting to fingerprinting. She found that the act of unlocking “far exceeds” submission to fingerprinting, because the suspect’s fingerprints must then be matched to another set of fingerprints to confirm access to a crime scene. Additionally, using a fingerprint to simply confirm presence at a location is “starkly different” given how a smartphone may provide access to sensitive personal information, such as medical and financial records.

Judge Westmore also found that the foregone conclusion exception did not apply.1 Because of the vast quantities of information smartphones contain, she reasoned that the devices should be subject to different treatment and increased protection compared to storage devices courts have traditionally considered, such as safes. Relying on Riley v. California, 134 S. Ct. 2473 (2014), Judge Westmore noted that the Government lacked the prior knowledge required for the foregone conclusion exception to apply because it could not possibly anticipate the large swaths of data, “including GPS location data and sensitive records,” that could be accessed on an unlocked device.

Other courts addressing Fifth Amendment protections for biometric features

Rather than being a one-off, Oakland was the latest installment in a developing conversation about whether, and to what extent, the Fifth Amendment will have an independent role to play in reassessing commonly held views – such as the constitutionality of compelling the production of fingerprints – in the information age. For example, in In re Application for a Search Warrant, 236 F. Supp. 3d 1066 (N.D. Ill. 2017), the court’s analysis of a warrant application similar to that in Oakland assessed compelled use of biometric unlocking features under both the Fourth and Fifth Amendments. There, the court also suggested that the forced use of biometric features was testimonial for Fifth Amendment purposes, though it did note that in some cases, the foregone conclusion exception might apply such that similar future requests may not always be problematic.

Other courts have disagreed, holding the Fifth Amendment not to prohibit compelling the use of biometric unlocking features. For example, in In the Matter of Search of [Redacted], 317 F. Supp. 3d 523 (D.D.C. 2018), the court found that the requested warrant was permissible under both the Fourth and Fifth Amendments, and that the compelled use of biometric features was non-testimonial. The [Redacted] court reasoned that the compelled use of biometric features is “more akin to the surrender of a safe’s key than its combination,” and that the person unlocking the phone in such a manner does not “put any thought at all into the seizure.” Similarly, in State v. Diamond, 905 N.W.2d 870 (2018), the Supreme Court of Minnesota ruled that compelled use of a fingerprint to unlock a cellphone was not testimonial because the person involved “did not even need to be conscious” to provide the fingerprint. Further, even if mental processes were involved, the real inquiry was not simply whether the compelled content comes from the mind, but whether the mental content has “testimonial significance.”

So while searches and seizures are inevitably evaluated under the Fourth Amendment, courts are increasingly finding that accessing the fruits of those searches has a crucial Fifth Amendment element as well. While it is true that, prior to the advent of smartphones with fingerprint-centric security measures, the ability to take fingerprints or otherwise assess a suspect’s physical characteristics was uncontroversial from a constitutional standpoint, technological advances have offered opportunities for courts to reassess where searches might implicate the Fifth Amendment in addition to the Fourth.


  1. The foregone conclusion exception permits the compelling of information when the existence and location of subpoenaed documents are a foregone conclusion and the witness adds little to law enforcement’s body of information by conceding his or her possession of the documents.