Skip navigation
CLN bookstore

NACDL Fourth Amendment Center Compelled Decryption Primer, 2019

Download original document:
Brief thumbnail
This text is machine-read, and may contain errors. Check the original document to verify accuracy.
Reprinted With Permission from the National
Association of Criminal Defense Lawyers, 2019.
To download the original PDF of this primer,
please visit

Compelled Decryption Primer
The Supreme Court recognized in Riley v. California that cell phones

The majority of Americans now own several devices that are encrypted

are unlike other types of physical objects. 134 S.Ct. 2473 (2014).

until unlocked by a passcode or biometric mechanism.

Instead, the Court held, they are minicomputers that contain the

passcode can be a secret number, pattern, or alphanumeric

most intimate details of life. Due to their immense storage

password. Biometric locks may use a fingerprint or face scan.

capacity, combined with the many distinct types of private data


they contain, the Court held that the Fourth Amendment requires

unreadable until unlocked and decrypted by an authorized user.







contents inaccessible and

law enforcement to get a warrant to search a cell phone, even
While the lawfulness of a device search is a Fourth Amendment issue,

incident to arrest.

the Fifth Amendment privilege against self-incrimination is the

But if a device is locked or encrypted, can law enforcement compel


a suspect to unlock or decrypt it? This primer outlines the state of

successfully assert this right, the act of decryption must be

the law on compelled decryption and offers a guide for defense

compelled, incriminating, and “testimonial.” While the first two

lawyers on this important emerging issue.






requirements are often easily met, the key question is whether
decryption is testimonial.

Is Compelling Decryption “Testimonial”?
The act of decrypting a device may be “testimonial” under the Fifth Amendment if it explicitly or implicitly conveys the fact that certain data exists
or is in the possession, custody, or control of an individual. See In Re Grand Jury Subpoena Duces Tecum, 670 F.3d 1335 (11th Cir. 2012). Such an “act
of production” may itself be incriminating or effectively concede the “existence, possession and control, and authenticity” of
potentially incriminating evidence on a device. Id. at 1343. This analysis often hinges on the type of lock employed.

Numeric or Alphanumeric Locks: Courts have generally found that compelling individuals to provide their numeric
Enter Passcode

or alphanumeric passcode is potentially testimonial under the Fifth Amendment, as it forces the defendant to reveal
“the contents of his own mind.” In Re Grand Jury Subpoena Duces Tecum 670 F.3d at 1345; see also U.S. v. Apple MacPro
Computer, 851 F.3d 238 (3d Cir. 2017). It is analogous to compelling production of the combination to a wall safe, which
is testimonial, as opposed to surrendering the key to a strongbox, which is not. See Doe v. U.S., 487 U.S. 201, 220 (1988).
However, even if a court finds that providing the passcode is “testimonial,” it may still fall under the “foregone conclusion”
exception, which is addressed on the next page.

Biometric Locks: Some courts have found nothing testimonial under the
Fifth Amendment about compelling the production of biometric keys, such as a
fingerprint, similar to tests that gather physical evidence. See, e.g., State v. Diamond, 905
N.W.2d 870 (Minn. 2018); Matter of Search of [Redacted] Washington, D.C., 317 F. Supp.
3d 523 (D.D.C. 2018); Commonwealth v. Baust, 89 Va. Cir. 267 (Va. Cir. Ct. 2014).
Recently, however, others have begun to hold that compelling the production of a
biometric key is just as testimonial as a numeric one. See Matter of Residence in
Oakland, California, 354 F. Supp. 3d 1010, 1016 (N.D. Cal. 2019); In Re Application for a
Search Warrant, 236 F. Supp. 3d 1066 (N.D. Ill. 2017). From this perspective, “biometric
features serve the same purpose of a passcode, which is to secure the owner's content,
pragmatically rendering them functionally equivalent.” 354 F. Supp. 3d at 1015.


Is it a “Foregone Conclusion”?
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.” U.S. v. Hubbell, 530 U.S. 27, 45 (2000).
As a general rule, the “foregone conclusion” exception applies if the government can show it knows the location, existence, and authenticity
of the purported evidence with reasonable particularity. Id. at 27. But the Supreme Court has never applied the exception beyond business
documents, indicating an unwillingness to do so where more private and personal documents, like a diary, are at issue. Fisher v. U.S., 425 U.S.
391, 401 & n.7 (1976) (citing U.S. v. Bennet, 409 F.2d 888, 897 (2d Cir. 1969)). It is therefore essential to challenge whether the doctrine applies at
all in the digital context. The Court has repeatedly emphasized that cell phones are not like ordinary closed containers or physical objects. See
Riley, 134 S. Ct. at 2491 (“[A] cell phone search would typically expose to the government far more than the most exhaustive search of a house”);
Carpenter v. U.S., 138 S.Ct. 2206, 2220 (2018) (requiring a warrant for historical cell phone location information). Indeed, the breadth and depth
of private information contained in modern electronic devices simply did not exist when the Court established the foregone conclusion rule.
Defense counsel should argue that it does not apply in the context of digital devices, just as the Court declined to apply the search-incident-toarrest rule in Riley and the longstanding "third-party doctrine" in Carpenter.
In the alternative, the critical question is whether the government already knows of the existence and location of relevant files and can show
that the client can access them. In Re Grand Jury Subpoena Duces Tecum, 670 F.3d at 1346. Lower courts are currently split on the test for deciding
this question in the context of digital devices. Each of the tests is addressed below:

Reasonable Particularity Test: The Eleventh Circuit has held that the

Clear & Convincing Evidence Test: Some courts have rejected the

foregone conclusion rule applies only if the government can show with

Eleventh Circuit’s “reasonable particularity” test. In U.S. v. Spencer,

“reasonable particularity” that the purported evidence exists, is in a certain

for example, the court instead required “clear and convincing

location, and is authentic. By contrast, the rule does not apply if the

evidence” that the defendant could unlock his phone. No. 17 CR

government is unable to identify specific files or data that investigators

259, 2018 WL 1964588 (N.D. Cal. Apr. 26, 2018). This test shifts the

expect to find. See In Re Grand Jury Subpoena 670 F.3d at 1346; see also

goalposts in a way that is exceedingly unfavorable to the defense.

Apple MacPro Computer, 851 F.3d at 248-49 (applying Eleventh Circuit’s

Rather than needing to show that the files exist, are on the device,

test, but finding a foregone conclusion where a family member saw the

and are authentic, the Spencer court requires the government to

defendant navigate to child pornography on the encrypted device). This

show only that an individual can unlock his own phone, a low

is a high bar to meet, consistent with the high degree of constitutional

bar to clear in most cases.

protection that the Supreme Court has afforded to modern cell phones.

Other Potential Legal Arguments
Is Compelled Decryption Necessary or Appropriate?

Is the Search Warrant Overbroad?

When a suspect does not provide a passcode to decrypt a device, the

When presented with a warrant to search a device locked by a

government may invoke the All Writs Act for a court order to compel

biometric key, make sure to check that the warrant describes the

decryption “in aid of” a valid search warrant. See U.S. v. Apple

device to be searched, files expected to be found, and specific

MacPro Computer, 851 F.3d at 241-42. But, if the government has the

individuals law enforcement seek to compel to provide a

technical capability to decrypt the device itself, or can reasonably

biometric key. In In Re Application for a Search Warrant, 236 F.

acquire that ability, then an order compelling decryption is improper.

Supp. 3d 1066 (N.D. Ill. 2017), the court found that the search
warrant application lacked enough detailed information about

As private companies develop technologies that allow the
government to unlock and decrypt devices, the government should
be required to disclose any methods known or reasonably available
to it that could be used instead of ordering a suspect to provide
a passcode for an encrypted device or compelling a company

the devices to be searched, and residents of the premises to be
searched. The magistrate judge found that, in this case, the use of
a fingerprint to unlock a device would be testimonial because it
would communicate that the individual had accessed the device
before and had control over its contents. Id. at 1073; see also In

to assist in the search of a device. An All Writs Act order compelling

the Matter of the Search of a Residence in Oakland, California,

the suspect to decrypt a device is not “necessary or appropriate” if

No. 4-19-70053, 2019 WL 176937, at *3-5 (N.D. Cal. Jan. 10, 2019)

the government has other viable means of getting in.

(finding that the warrant's language was overbroad, and that the
use of a fingerprint to unlock the device was testimonial for
Fifth Amendment purposes).

State Jurisdictional Challenges
State courts may lack jurisdiction to issue a compelled decryption order if there is no state law granting judges such authority. While state law may
authorize courts to compel the production of evidence in certain circumstances, device decryption is likely not one of them, indicating that the
legislature did not intend to vest courts with this power. Federal courts have the general authority to compel the production of evidence “in aid of
their respective jurisdictions” under the All Writs Act, 28 U.S.C.A. § 1651, but similar provisions may not exist in state law. Consequently, any decryption
order issued by a state court may be vulnerable to jurisdictional challenges as well as constitutional ones.

Border Searches
If an individual is entering the United States, the government’s stated interest in national security at the border will often outweigh an individual’s
privacy rights. For more information on how your constitutional rights may be interpreted during a border search, please see NACDL’s primer
“Protecting Your Digital Devices at the Border,” available at:

Case List
Compelling A Passcode Is Testimonial:


In Re Grand Jury Subpoena Duces Tecum,
670 F.3d 1335 (11th Cir. 2012).


Passcode Is Testimonial, But The
Foregone Conclusion Applies:


Seo v. State, 109 N.E.3d 418 (Ind. Ct. App.),
transfer granted, opinion vacated, 119


N.E.3d 90 (Ind. 2018).


U.S. v Kirschner, 823 F. Supp. 2d 665 (E.D.


Mich. 2010).


G.A.Q.L. v. State, 257 So.3d 1058 (Fla. Dist.


Ct. App. Oct. 24, 2018).


SEC v. Bonan Huang, 2015 WL 5611644
(E.D. Pa. 2015).

Compelling Biometric Decryption Is


In Re Application for a Search Warrant, 236
F. Supp. 3d 1066 (N.D. Ill. 2017).
Matter of Residence in Oakland, California,
354 F. Supp. 3d 1010 (N.D. Cal. 2019).

Biometric Decryption Is Not Testimonial:


State v. Diamond, 905 N.W.2d 870


(Minn. 2018).
Matter of Search of [Redacted] Washington,
D.C., 317 F. Supp. 3d 523 (D.D.C. 2018).


U.S. v. Spencer, No. 17-cr-00259-CRB-1,
2018 WL 1964588 (N.D. Cal. April 26,
Commonwealth v. Baust, 89 Va. Cir. 267
(Va. Cir. Ct. 2014).
Commonwealth v. Jones, 481 Mass. 540
U.S. v. Friscosu, 841 F. Supp. 2d 1232 (D.
Colo. 2012).
State v. Stahl, 206 So. 3d 124 (Fla. Dist.
Ct. App. 2016).
U.S. v. Apple MacPro Computer, 851
F.3d 238 (3d Cir. 2017).

Fifth Amendment Privilege Against
Self-Incrimination Generally:


U.S. v. Hubbell, 530 U.S. 27 (2000).
Fisher v. U.S., 425 U.S. 391 (1976).
U.S. v. Doe, 465 U.S. 605 (1984).
Hoffman v. U.S., 341 U.S. 479 (1951).
Doe v. U.S., 487 U.S. 201, 220 (1988).

Additional Resources
the Digital


Aloni Cohen and Sunoo Park, Compelled
Decryption and the Fifth Amendment:
Exploring the Technical Boundaries, 32 HARV.
J.L. & TECH. 169 (2018).


Efren Lemus, When Fingerprints Are Key:
Reinstating Privacy to the Privilege Against
Self-Incrimination in Light of Fingerprint
Encryption in Smartphones, 70 SMU L. REV. 533


Laurent Sacharoff, Unlocking the Fifth
Amendment: Passwords and Encrypted
Devices, 87 FORDHAM L. REV. 203 (2018).


Jason Wareham, Cracking the Code: The
Enigma of the Self-Incrimination Clause and
Compulsory Decryption of Encrypted Media, 1
GEO. L. TECH. REV. 247 (2017).


Hanni Fakhoury, A Combination or a Key? The
Fifth Amendment and Privilege Against
Compelled Decryption, 9 DIGITAL EVIDENCE &

U.S. v. Patane, 542 U.S. 630 (2004).



U.S. v. Djibo, 151 F. Supp. 3d 297 (E.D.
N.Y. 2015) (passcode suppressed as
an un-Mirandized statement).
U.S. v. Gavegnano, 305 Fed. App'x. 954
(4th Cir. 2009) (no expectation of
privacy in a gov't-issued computer).

Lacambra, Defending Against
Dragnet: Fighting Compelled
Disclosure and Decryption,
Frontier Foundation, Oct. 31,


For litigation assistance and other resources, contact



Federal Prison Handbook - Side
CLN Subscribe Now Ad
CLN Subscribe Now Ad 450x600