As we come to rely on our smartphones more and more, it becomes reasonable to ask whether the Fifth Amendment privilege against self-incrimination protects one from having to unlock a phone for law enforcement. The short answer to the question of whether one can be compelled to unlock their cell phone for law enforcement is “maybe.”
Most modern smartphones are opened using the owner’s fingerprint. The Supreme Court, in U.S. v. Wade, held that the Fifth Amendment privilege against self-incrimination offers no protection against compulsion to submit to fingerprinting. However, the case law that determines that was decided in the context of utilizing fingerprinting solely for identification purposes.
In the context of the Fifth Amendment, current technology allows one’s fingerprint for at least three starkly different scenarios: (1) using a fingerprint to identify someone; (2) using a fingerprint to place someone at a specific location; or (3) using a fingerprint to access a database of someone’s most private information. The Wade court could only foresee the first two situations and could not have anticipated that its holding would be applied in such a far-reaching manner as implied by the third scenario.
The Supreme Court has held that an individual must show three things to fall within the ambit of the Fifth Amendment: (1) compulsion, (2) a testimonial communication or act, and (3) incrimination.
It is obvious that in a criminal prosecution, the Government may often seek to compel the defendant to decrypt and hand over the contents of the smartphone at issue which, the Government believes likely to contain incriminatory evidence. 
The crux of the dispute is whether the Government seeks “testimony” within the meaning of the Fifth Amendment. It could be argued that the Government merely wants the defendant to hand over pre-existing and voluntarily created files, not to testify. It can be conceded that the files, if any, contained on the phone are not ipso facto testimonial.
Whether such files are testimonial, however, is not the issue. The issue is whether the act of production may have some testimonial quality enough to trigger Fifth Amendment protection when the production explicitly or implicitly conveys some statement of fact. Thus, the issue turns on whether the act of decryption and production would be testimonial. 
An act of production can be testimonial when that act conveys some explicit or implicit statement of fact that certain materials exist, are in the subpoenaed individual’s possession or control, or are authentic. An act of production is testimonial when the government compels the individual to use “the contents of his own mind” to explicitly or implicitly communicate some statement of fact. 
Put another way, the Supreme Court has marked out two ways in which an act of production is not testimonial. First, the Fifth Amendment privilege is not triggered where the Government merely compels some physical act, i.e. where the individual is not called upon to make use of the contents of his or her mind. The most famous example is the key to the lock of a strongbox containing documents, but the High Court has also used this rationale in a variety of other contexts. 
Under the “foregone conclusion” doctrine, an act of production is not testimonial—even if the act conveys a fact regarding the existence or location, possession, or authenticity of the subpoenaed materials—if the Government can show with “reasonable particularity” that, at the time it sought to compel the act of production, it already knew of the materials, thereby making any testimonial aspect a “foregone conclusion.” 
It could be argued that the Government does not seek the key to a lock, but rather the contents of the smartphone. This argument fails, however, because in Fisher, where the analogy was born, and again in Hubbell, the Government never sought the “key” to a lock for its own sake; rather, the Government sought the files being withheld.  Requiring a decryption password (or replacement for one, such as a fingerprint scan) is more akin to requiring the production of a key to a safe because both demand the use of the contents of the mind, and the production is accompanied by the implied factual statements noted above that could prove to be incriminatory.
To be fair, it is obvious that the Government can show a modern smart phone can contain hundreds, if not thousands, of files, and that those files are encrypted as a matter of course. What the People must show, however, is that the phone contains any files at all, and which files the phone contains that may prove useful.  Simply because the phone is encrypted does not necessarily mean the defendant is trying to hide something. The Government must show that it had prior knowledge of either the existence or the whereabouts of the files that it seeks to compel the defendant to produce. 
Therefore, the act of a defendant’s decryption and production of the contents of their smartphone sufficiently implicates the Fifth Amendment privilege in most cases. This is because (1) the defendant’s decryption and production of the contents of the drives would be testimonial, not merely a physical act; and (2) the explicit and implicit factual communications associated with the decryption and production are not foregone conclusions. 
The decryption and production of the phone’s contents would require the use of the contents of the defendant’s mind and could not be fairly characterized as a physical act that would be non-testimonial in nature. 
is tantamount to testimony by the defendant of his knowledge of the existence
and location of potentially incriminating files; of his possession, control,
and access to the encrypted portions of the drives; and of his capability to
decrypt the files. 
The “foregone conclusion” doctrine is likely to be inapplicable
because Government often has no knowledge of whether any files exist or the
location of those files on the phone. 
 U.S. v. Wade,388 U.S. 218 (1967).
 United States v. Doe (In re Grand Jury Subpoena Duces Tecum), 670 F.3d 1335 (11th Cir. 2012); See also United States v. Ghidoni, 732 F.2d 814, 816 (11th Cir. 1984) (citing United States v. Authement, 607 F.2d 1129, 1131 (5th Cir. 1979) (per curiam)).
 Doe, 670 F.3d at 1341-42.
 See United States v. Hubbell, 530 U.S. 27, 35-36 (2000) (noting that it is a “settled proposition that a person may be required to produce specific documents even though they contain incriminating assertions of fact or belief because the creation of those documents was not ‘compelled’ within the meaning of the privilege”).
 Doe, 670 F.3d at 1341-42
 See Fisher v. United States, 425 U.S. 391 (1976) (“The act of producing evidence in response to a subpoena nevertheless has communicative aspects of its own, wholly aside from the contents of the papers produced.”).
 Fisher, 425 U.S. at 410-11; 391 Doe, 670 F.3d at 1341-42.
 See Hubble, 530 U.S. at 36.
 . Doe, 670 F.3d at 1345 (citing Curcio v. United States, 354 U.S. 118, 128 (1957).
 , see Hubbell, 530 U.S. at 43 (citing Doe v. United States, 487 U.S. 201, 210 )
 Doe, 670 F.3d at 1346
 Hubbell, 530 U.S. at 38 (trying to compel production of documents); Fisher, 425 U.S. at 394-95 (seeking to access contents possessed by attorneys).
 See Hubbell, 530 U.S. at 43.
 Doe, 670 F.3d at 1346.
 Hubbell, 530 U.S. at 45.
 Doe, 670 F.3d at 1346