by Christopher J. Rydberg*

In the digital age, how should privacy concerns constrain police investigations? In this Contribution, Christopher J. Rydberg considers this problem with respect to forcing suspects to unlock smartphones and specificity requirements with respect to smartphone search warrants. Ultimately, the Contribution argues that smartphones are different in kind because of the massive scope of data they contain, and thus historical doctrines of police process will have to change to accommodate the smartphone era.

Advances in technology raise new and challenging questions for courts in interpreting the protections of the Fourth and Fifth Amendments. As the Supreme Court noted in Riley v. California, searches of cell phones “typically expose to the government far more [private information] than the most exhaustive search of a house,” and the “possible intrusion on privacy is not physically limited in the same way when it comes to cell phones.”1 Cell phones have the capacity to store vast amounts of private information about our everyday lives,2 and the distinct and diverse types of data they may store tend to expose to law enforcement officers a complete picture of the owner’s life. As Justice Sotomayor noted in United States v. Jones, individual, discrete pieces of information — even if not individually private or incriminating — may in sum become a mosaic, revealing the most intimate details of an individual’s life.3

These unique concerns pose challenges to courts seeking to ensure that the Fourth and Fifth Amendments retain meaning in the digital age. Balancing law enforcement interests against individual privacy rights, and the right against self-incrimination, requires heightened judicial scrutiny and management to ensure that law enforcement does not run roughshod over civil liberties while in pursuit of suspects. This is even more important in the age of terrorism, as the fear of terror can blind government actors in their attempts to prevent another attack, focusing single-mindedly on their target while ignoring countervailing constitutional privacy considerations. Accordingly, this Contribution will argue that the Fifth Amendment prevents government actors from physically compelling subjects to unlock their cell phones with their fingerprint and thereby obtaining incriminating evidence. This Contribution will also argue that the Fourth Amendment requires greater particularity in cell phone searches, specifying how the phone will be searched, and that the use of the plain view doctrine in cell phone searches is inconsistent with Fourth Amendment reasonableness requirements.


The Fifth Amendment to the U.S. Constitution provides that no person “shall be compelled in any criminal case to be a witness against himself.”4 The Fifth Amendment protects a wide range of compelled communications deemed to be testimonial, or communicative, in nature.5 In particular, the Fifth Amendment protects against government compulsion by means of force or other coercive techniques.6 Included in these protections are any “testimonial materials, such as books and papers,” because these things “are generally little more than an extension of [one’s] person.”7 The amendment does not, however, guard against compulsion of evidence that is merely demonstrative, or non-testimonial, in nature.8 This non-testimonial exception to the privilege against self-incrimination encompasses several types of physical evidence, including: voice exemplars,9 handwriting exemplars,10 participation in lineups,11 blood samples,12 clothing,13 and the collection of fingerprints during the post-arrest booking process.14

The Fourth Amendment of the U.S. Constitution protects against unjustified government intrusion into the private affairs of citizens.15 The Amendment contains two principal clauses – the Reasonableness Clause and the Warrant Clause.16 Generally, the Fourth Amendment holds that a search is unreasonable unless conducted with a warrant supported by probable cause.17

For a warrant to comply with the Fourth Amendment of the U.S. Constitution, it must be based on probable cause and be reasonable, and it must “particularly describ[e] the place to be searched, and the persons or things to be seized.”18 This requirement to describe with particularity where the search would take place and what will be seized arose as a protection against general warrants, which permitted law enforcement the wide-ranging authority to search at will without meaningful checks.19 As such, when searching physical locations, warrants should be tailored to specific locations where there is probable cause to believe evidence is likely to be found.20 “If police approach a magistrate with an informant’s testimony that Sally Suspect is involved in narcotics trafficking, the magistrate should not automatically issue a warrant for Sally’s house, her office, her car, and her person.”21 Similarly, within physical structures, the same constraints apply — police may only search where the evidence may reasonably be found.22

There are, however, exceptions to this general preference for warrants. The “plain view” doctrine is one of them.23 This seizure is permissible even without a warrant because it would not produce an additional invasion of privacy.24 For a seizure of evidence under the plain view exception to be permissible, the item must be in plain view of an officer who is legitimately on the premises with a lawful right of action to the object, and it must be immediately apparent that the object in question is contraband.25


The coerced unlocking of a suspect’s cell phone by use of her fingerprint should be deemed testimonial because it demonstrated her control over the phone. The Supreme Court has held that the act of producing documents could be deemed testimonial, by virtue of the fact that the production communicated ownership and control over the evidence.26 Although the Court in Fisher held that the nature of production should be determined on a case-by-case basis, rather than implementing a bright-line rule, its reasoning demonstrates that there are at least some times when the act of producing evidence could itself be testimonial.27 The forced unlocking of a smartphone should be deemed one of those testimonial acts of production. The act of unlocking a cell phone with a fingerprint demonstrates control over the phone and the communicative evidence contained therein, as the biometric encryption is a direct link to testimonial material within the phone. The Supreme Court’s jurisprudence protects evidence that is a “link in the chain” to communicative evidence, even if that link would not normally receive Fifth Amendment protection. As the Court noted in Hoffman v. United States, “[t]he privilege afforded not only extends to answers that would in themselves support a conviction under a federal criminal statute but likewise embraces those which would furnish a link in the chain of evidence needed to prosecute the claimant for a federal crime.”28 Similarly, in United States v. Hubbell, the Court noted that information “that may ‘lead to incriminating evidence’ is privileged even if the information itself is not inculpatory.”29 The use of an individual’s fingerprint to unlock her cell phone is exactly such a link and thus deserves Fifth Amendment protection.

The forced use of an individual’s fingerprint to open her cell phone should be viewed in light of the purpose for which the fingerprint was used: as a passcode and a means to access vast quantities of highly personal information contained on the phone. Physically forcing a suspect to place her finger on her phone and unlock it falls squarely within the evil intended to be prevented by the Fifth Amendment.30 Such physical coercion to produce incriminating evidence is incompatible with the basic tenets of the Fifth Amendment.

This purpose-driven analysis is particularly important given the artificial distinction a contrary position would create. Currently, forcing an individual to divulge a passcode would run afoul of Fifth Amendment protections, while compelling production of a physical key would not.31 Accordingly, in United States v. Kirschner, the Government issued a subpoena for passwords to the defendant’s computer, seeking evidence of child pornography.32 The District Court held this to be a violation of the Fifth Amendment privilege, ruling that the production of the passwords was testimonial and divulged information that Kirschner knew would convict him.33

A mechanical application of Fifth Amendment precedent may relate a fingerprint to a key, but such a reading misses the forest for the trees and eviscerates the Amendment’s protection in the digital era. The fingerprint, as used to unlock a cell phone, is far more than mere identification that the Schmerber Court contemplated. It is a direct link to communicative and possibly incriminating evidence. Contrary holdings would create the perverse result that the Fifth Amendment protects the consumer who choses to use a password, but not the individual who used biometric protection — even though the latter makes her choice knowing that biometric encryption is more secure than a four-digit passcode.34 This is a distinction without a difference, for both the passcode and the fingerprint are simply the means to access testimonial content on the phone. This would be an untenable and illogical result — the consumer who seeks extra protection through biometric security in the end receives less.

Search warrants that purport to authorize broad searches of all data contained on a cell phone should be deemed overbroad and without the particularity demanded by the Fourth Amendment. Generally, electronic searches present very significant challenges to the particularity requirement. Advancements in technology mean that vast amounts of data can be stored on a hard drive that fits in a pocket. In particular, the modern smartphone functions in such a wide variety of ways — phone, calendar, email, texting, location tracking — that a search without guidelines to cabin government discretion could reveal the most intimate aspects of our lives. The risk in electronic search cases of those “wide-ranging exploratory searches” prohibited by the Fourth Amendment is heightened.35 As a result, where search warrants have purported to authorize broad searches of electronic equipment, courts have held the warrant to violate the particularity requirement.36 Absent restrictions, the government could search through the entirety of a suspect’s phone and its many applications. Such a broad search closely resembles the general warrants so reviled at the founding,37 and for that reason, warrants authorizing searches of the entirety of a cell phone cannot pass constitutional muster.

The plain view doctrine’s application to digital evidence, and to cell phones in particular, poses similar challenges. For both computers and cell phones, hard drives can store vast amounts of private information about our everyday lives. Modern cellphones compound these concerns, because they function as “cameras, video players, rolodexes, calendars, tape recorders, libraries, diaries, albums, televisions, maps, [and] newspapers” all at once, in a compact package that will fit in the palm of your hand.38 In this sense, they are qualitatively different from, for example, a storage cabinet — not merely because their storage capacity exceeds even a room full of filing cabinets, but because of the myriad types of documents they can hold.

The fact that digital devices, including computers and phones, can hold such a variety of documents presents a challenging question for the application of the plain view doctrine. When law enforcement searches electronic devices, it is not just possible but in fact highly likely that they will encounter private information that is unrelated to the target of the search, even if the search is extremely focused.39 This lack of effective constraints on where and how law enforcement may search leads to a weakening of the particularity requirement and runs the risk of permitting general warrants, the very evil the Fourth Amendment sought to remedy.40 “[D]igital evidence diminishes the regulatory effect of the particularity requirement” because the evidence sought could be located anywhere on the hard drive or cell phone and thus increases the frequency with which the plain view doctrine could be invoked on finding unrelated but nonetheless incriminating evidence.41 Searching a cell phone or a computer is qualitatively different than tangible objects, because the “possible intrusion on privacy is not physically limited in the same way when it comes to cell phones.”42

These significant concerns counsel in favor of rejecting the plain view doctrine in electronic search cases and for requiring greater particularity in search warrants for cell phones. These protocols are critical to preserving the core purpose and integrity of both the Fourth Amendment and the plain view exception to the preference for warrants. In the case of digital searches, allowing the plain view doctrine to exist would allow the exception to swallow the rule — that is, any search warrant for a computer or cell phone would become functionally a general warrant, allowing law enforcement to search through each individual file or piece of information. Untethered from its grounding in the reasonableness clause of the Fourth Amendment, the plain view exception would allow “[t]he process of segregating electronic data that is seizable [sic] from that which is not . . . [to] become a vehicle for the government to gain access to data which it has no probable cause to collect.”43

Riley supports the proposition that electronic searches should be treated differently than other searches of physical objects or locations. In Riley, the Court singled out the unique qualities of cell phones and how they present novel privacy concerns in holding that the search incident to a lawful arrest exception does not apply to cell phones.44 Those same unique qualities of cell phones also dictate that the plain view exception should not apply. “The existing plain view exception remains rooted in the contingent dynamics of physical evidence collection,”45 while the relatively new world of digital evidence presents vastly different concerns about the scope of government intrusion. Specifically, the Riley Court noted that “[a] conclusion that inspecting the contents of an arrestee’s pockets works no substantial additional intrusion on privacy beyond the arrest itself may make sense as applied to physical items, but any extension of that reasoning to digital data has to rest on its own bottom.”46 The same concerns that animated the Court in Riley to carve out a cell-phone exception to the search incident to arrest doctrine are at play here as well, and call for the creation of a similar exception.

The balance between law enforcement and privacy interests — carefully established over decades — has been upended by rapid advancements in technology. It is critical that courts respond appropriately to these advances rather than mechanically applying precedent more appropriately suited to the collection of physical evidence.47 The Fifth Amendment must be held to protect a suspect from being physically compelled to provide her fingerprint to unlock her cell phone. Similarly, the Fourth Amendment’s protections should apply equally, if not more so, for cell phones and other digital evidence. Warrants should specify with particularity what specifically on the phone will be searched and how. Finally, the plain view doctrine should not apply in this case. As an exception to the general preference for warrants, it no longer has its intended effect in the context of digital searches, and accordingly should not be permitted.

* Christopher J. Rydberg is a 2L at New York University School of Law. This piece is a commentary on the 2017 Evan A. Evans Constitutional Law Moot Court Competition hosted by the University of Wisconsin Moot Court Board. The fact pattern of the competition involved law enforcement seeking to search the cell phone of an individual believed to be part of a fictional terrorist organization. Law enforcement obtained a warrant that authorized a search of “any and all data” on the phone related to the terrorist network. The questions presented were whether the Fifth Amendment prevented law enforcement from physically compelling the defendant to unlock his cell phone with his fingerprint, whether the search warrant lacked particularity under the Fourth Amendment, and whether the plain view exception to the warrant requirement should apply in cell phone searches. The views expressed in this article do not necessarily represent the views of the author on this point of law. Rather, this article is a distillation of one side of an argument assigned to the author at the 2017 Evan A. Evans Constitutional Law Moot Court Competition.

1. Riley v. California, 134 S. Ct. 2473, 2491, 2489 (2014) (emphasis in original).

2. See Orin S. Kerr, Searches and Seizures in a Digital World, 119 Harv. L. Rev. 532, 532 (2005).

3. United States v. Jones, 565 U.S. 400, 416 (2012) (Sotomayor, J., dissenting) (questioning “whether people reasonably expect that their movements will be recorded and aggregated in a manner that enables the Government to ascertain, more or less at will, their political and religious beliefs, sexual habits, and so on.”).

4. U.S. Const. amend. V (“No person . . . shall be compelled in any criminal case to be a witness against himself”).

5. See Fisher v. United States, 425 U.S. 391, 409 (1976).

6. See Holt v. United States, 218 U.S. 245, 252-53 (1910); see also United States v. White, 322 U.S. 694, 698 (1944) (explaining that “[t]he constitutional privilege against self-incrimination . . . is designed to prevent [the government from] forc[ing] from the lips of the accused individual the evidence necessary to convict him or to force him to produce and authenticate any personal documents or effects that might incriminate him.”).

7. Fisher, 425 U.S. at 420 (1976) (Brennan, J., concurring).

8. See Schmerber v. California, 384 U.S. 757, 764 (1966) (“[T]the privilege is a bar against compelling ‘communications’ or ‘testimony,’ but that compulsion which makes a suspect or accused the source of ‘real or physical evidence’ does not violate it.”).

9. United States v. Dionisio, 410 U.S. 1, 7 (1973).

10. Gilbert v. California, 388 U.S. 263, 266-67 (1967).

11. United States v. Wade, 388 U.S. 218, 221-22 (1967).

12. Schmerber, 384 U.S. at 765.

13. Holt v. United States, 218 U.S. 245, 252-53 (1910).

14. See Schmerber, 384 U.S. at 764 (“[B]oth federal and state courts have usually held that [the Fifth Amendment] offers no protection against compulsion to submit to fingerprinting.”).

15. See U.S. Const. amend. IV.

16. See Luis G. Stelzner, The Fourth Amendment: The Reasonableness and Warrant Clauses, 10 N.M. L. Rev. 33, 33 (1979).

17. See, e.g., California v. Carney, 471 U.S. 386, 390 (1985) (“This fundamental right is preserved by a requirement that searches be conducted pursuant to a warrant issued by an independent judicial officer.”).

18. U.S. Const. amend. IV.

19. See, e.g., Ashcroft v. al-Kidd, 563 U.S. 731, 742 (2011) (“The Fourth Amendment was a response to the English Crown’s use of general warrants, which often allowed royal officials to search and seize whatever and whomever they pleased while investigating crimes or affronts to the Crown.”).

20. See, e.g., United States v. George, 975 F.2d 72, 76 (2d Cir. 1992) (“Absent some limitation curtailing the officers’ discretion when executing the warrant, the safeguard of having a magistrate determine the scope of the search is lost.”)

21. Adam M. Gershowitz, The Post-Riley Search Warrant: Search Protocols and Particularity in Cell Phone Searches, 69 Vanderbilt L. Rev. 585, 589 (2015).

22. See id. (“If police have a search warrant for a stolen fifty-inch television, they cannot look in the microwave.”).

23. See Coolidge v. New Hampshire, 403 U.S. 443, 465 (1971) (plurality opinion) (“It is well established that under certain circumstances the police may seize evidence in plain view without a warrant.”).

24. See Arizona v. Hicks, 480 U.S. 321, 325 (1987) (noting that an inspection of items in plain view “would not have constituted an independent search, because it would have produced no additional invasion of respondent’s privacy interest”).

25. See Horton v. California, 496 U.S. 128, 136-37 (1990) (holding that a plain view seizure requires the “incriminating character must . . . be ‘immediately apparent’” and that the officer must “have a lawful right of access to the object itself”).

26. See Fisher v. United States, 425 U.S. 391, 410 (1976) (“[T]he act of producing evidence in response to a subpoena nevertheless has communicative aspects of its own”).

27. Id. (“These questions perhaps do not lend themselves to categorical answers; their resolution may instead depend on the facts and circumstances of particular cases or classes thereof.”).

28. Hoffman v. United States, 341 U.S. 479, 486 (1951).

29. United States v. Hubbell, 530 U.S. 27, 38 (2000) (quoting Doe v. United States, 487 U.S. 201, 208, n.6 (1988)).

30. See United States v. White, 322 U.S. 694, 698 (1944) (“Physical torture and other less violent but equally reprehensible modes of compelling the production of incriminating evidence are thereby avoided.”).

31. See Hubbell, 530 U.S. at 41 (finding that Fifth Amendment would protect against forced disclosure of “combination to a wall safe,” but “not being forced to surrender the key to a strongbox”).

32. See United States v. Kirschner, 823 F. Supp. 2d 665, 666 (E.D. Mich. 2010).

33. Id. at 669.

34. See About Touch ID security on iPhone and iPad, Apple (Nov. 3, 2015), (“Your fingerprint is one of the best passcodes in the world.”).

35. See Maryland v. Garrison, 480 U.S. 79, 84 (1987).

36. See United States v. Zemlyansky, 945 F. Supp. 2d 438, 458 (S.D.N.Y. 2013) (disallowing a warrant for “indiscriminately permit[ting] the search of all [c]omputers and [t]humb drives” for lacking particularity); United States v. Rosa, 626 F.3d 56, 58 (2d Cir. 2010) (finding that a warrant permitting officers to search “computer equipment” and “electronic digital storage media” lacked particularity).

37. See Ashcroft v. al-Kidd, 563 U.S. 731, 742-43 (2011) (“The Fourth Amendment was a response to the English Crown’s use of general warrants, which often allowed royal officials to search and seize whatever and whomever they pleased while investigating crimes or affronts to the Crown.”).

38. Riley v. California, 134 S. Ct. 2473, 2489 (2014).

39. See Kerr, supra note 2, at 538.

40. See id. at 565 (noting that “computer technologies may allow warrants that are particular on their face to become general warrants in practice”).

41. Id.

42. Riley, 134 S. Ct. at 2489.

43. United States v. Comprehensive Drug Testing Inc., 621 F.3d 1162, 1177 (9th Cir. 2010).

44. See Riley, 134 S. Ct. at 2489.

45. Kerr, supra note 2, at 571.

46. Riley, 134 S. Ct. at 2489.

47. As the Court in Riley noted, saying digital evidence should be treated just like physical evidence “is like saying a ride on horseback is materially indistinguishable from a flight to the moon. Both are ways of getting from point A to point B, but little else justifies lumping them together.” Riley, 134 S. Ct. at 2488.