Police have your phone.
They have a warrant authorizing them to search it.
There is just one problem.
They cannot get inside.
The device is protected by a passcode, fingerprint or facial-recognition system, and investigators want you to unlock it for them.
Can the government make you do it?
The answer is more complicated than the question.
A search warrant can give investigators legal authority to search a device, but that does not necessarily resolve whether the person who owns or controls the phone can be compelled to help them gain access.
That second question can implicate the Fifth Amendment's protection against compelled self-incrimination.
And unlike the Supreme Court's relatively clear rule requiring police generally to obtain a warrant before searching the digital contents of a phone seized during an arrest, the law governing compelled unlocking remains more unsettled.
Courts have had to apply constitutional principles developed long before smartphones existed to devices capable of protecting enormous quantities of information behind a few digits—or a person's face.
Having a Warrant and Being Able to Unlock the Phone Are Different Problems
Suppose investigators obtain a valid search warrant for a house.
The warrant gives them legal authority to conduct the search described by the warrant.
But imagine that investigators encounter a locked safe inside.
The authority to search and the practical ability to gain access are related, but they are not identical questions.
Smartphones create a digital version of that problem.
A warrant may establish the government's authority to search information on a device. Encryption may still prevent investigators from reading it.
Investigators might attempt to unlock the device technologically.
They might obtain information through another source.
Or they might seek an order requiring someone to assist in unlocking it.
At that point, the question is no longer simply whether the government may search.
It becomes whether the government may compel a person to do something that makes the search possible.
The Fifth Amendment Protects Testimony, Not Every Form of Evidence
The Fifth Amendment says that no person shall be compelled in a criminal case to be a witness against himself.
That protection is sometimes described too broadly.
The Fifth Amendment does not mean the government can never compel a person to provide evidence that might be incriminating.
Courts have long distinguished between compelled testimonial communication and the compelled production or display of certain physical characteristics.
For example, the Supreme Court has treated things such as fingerprints, voice exemplars and some physical evidence differently from compelled testimony.
That distinction creates the central problem with locked phones.
Is unlocking the phone more like giving investigators a physical key?
Or is it more like telling them the secret combination to a safe?
The answer can matter enormously.
A Memorized Passcode Exists in the Mind
Consider a phone protected by the passcode:
6-2-9-4-1-8.
Investigators cannot determine the code.
Only the owner knows it.
If the government orders that person to state the passcode aloud, it is requiring the person to reveal information stored in his or her mind.
That looks much more like traditional testimony than providing a fingerprint.
The Justice Department itself has recognized the constitutional problem. A federal prosecution bulletin discussing device access explained that compelling a password can require a testimonial communication implicating the Fifth Amendment, while also noting circumstances in which the government's prior knowledge may affect the analysis.
But even that does not end the inquiry.
A doctrine known as the foregone conclusion doctrine can become important.
The Government May Argue That You Aren't Telling It Anything It Doesn't Already Know
The foregone-conclusion doctrine developed from cases involving compelled production of evidence.
The basic idea is that an act of producing something can itself communicate facts.
Imagine investigators order someone to produce a particular document.
By producing it, the person may implicitly communicate:
The document exists.
I possess or control it.
This is the document you asked for.
Those implied statements can sometimes have testimonial significance.
But if the government can already establish those facts with sufficient particularity, it may argue that the act of production adds little or nothing testimonial—the relevant facts are already a “foregone conclusion.”
Applying that doctrine to encrypted phones has produced difficult disputes.
What exactly must the government already know?
That the phone belongs to the person?
That the person knows the passcode?
That the person can unlock it?
That particular files exist inside?
Courts have not always answered those questions the same way.
Entering the Code Can Communicate Something Even Without Saying It
Suppose the government does not require someone to reveal the passcode.
Instead, investigators hand the person the phone and say:
“Type the code in yourself. Don't tell us what it is.”
At first, that may seem different.
Investigators never learn the digits.
But the act of successfully unlocking the phone can still communicate information.
It can demonstrate that the person knows how to unlock the device.
It may indicate possession or control.
And depending on the circumstances, investigators may argue—or the person may contest—that the act communicates additional facts about the relationship between that person and the phone.
This distinction has produced substantial litigation.
In a case arising from Illinois, for example, the state court concluded that compelling a defendant to enter a phone passcode was testimonial to the extent the act implicitly communicated that a passcode existed, the person possessed or controlled it, and the entered passcode was authentic. The parties then disputed whether those facts were already a foregone conclusion.
That illustrates why “the police never actually saw the password” does not necessarily resolve the Fifth Amendment question.
A Fingerprint Creates a Different Argument
Now replace the passcode with a fingerprint.
Investigators do not ask the person to remember or reveal anything.
They want to place a finger on the phone's sensor.
Historically, the Supreme Court has distinguished compelled testimony from the compelled display of physical characteristics.
That gives the government a strong argument that requiring a fingerprint is more like taking fingerprints during booking than forcing someone to reveal the contents of his or her mind.
The Justice Department has made precisely that argument, comparing biometric unlocking to use of a physical key rather than disclosure of a safe combination.
But courts have wrestled with whether smartphone biometrics are quite that simple.
The finger is physical.
What happens when the finger touches the phone, however, can reveal something else: that this person possesses a biometric characteristic capable of opening this particular device.
That is why biometric unlocking has generated its own line of constitutional disputes.
The Ninth Circuit Considered Compelled Thumbprint Unlocking
One important modern example involved Jeremy Payne.
Law enforcement compelled the use of Payne's thumb to unlock a phone.
The Ninth Circuit concluded that, under the Supreme Court framework it applied, the compelled use of the thumb was not testimonial for Fifth Amendment purposes. The court reasoned that the act required no cognitive exertion and placed it in the category of physical evidence rather than testimonial communication. A later Supreme Court petition challenging that analysis described the Ninth Circuit's reasoning and pointed to disagreement among lower courts.
That disagreement matters.
A person should not assume that every court will necessarily treat every form of biometric unlocking identically.
The technology, facts and governing precedent in the jurisdiction can affect the analysis.
Your Face Can Function Like a Key
Facial recognition makes the distinction even stranger.
The phone is locked.
The government points it toward someone's face.
The device recognizes the person's physical features and opens.
The person has not spoken.
No memorized information has been disclosed.
But access to potentially years of communications, photographs and records has been enabled.
From one perspective, this looks like using a physical characteristic, much like a fingerprint.
From another, the act confirms a relationship between the person and the device.
Courts have had to determine which aspect matters for Fifth Amendment purposes.
That question demonstrates how poorly some traditional analogies fit modern devices.
A human face was not historically a key capable of opening an archive of someone's digital life.
Now it can be.
The Phone Can Contain Far More Than Investigators Could Carry Away From a House
The stakes are high because unlocking a smartphone is not comparable to opening an ordinary container.
A modern phone can contain or provide access to photographs, messages, email, financial records, browsing activity, location information, health information, calendars and years of personal communications.
The Supreme Court recognized the extraordinary quantity and sensitivity of smartphone data in Riley v. California, when it held that police generally need a warrant before searching the digital contents of a phone seized during an arrest.
But Riley answered the Fourth Amendment search question.
It did not create a single nationwide rule resolving every Fifth Amendment dispute about compelled passcodes and biometrics.
Those are related constitutional issues, but they are not the same issue.
Encryption Created the Problem
None of this would matter very much if investigators could simply open every seized device.
Modern encryption makes that increasingly difficult.
When a properly secured device is locked, possessing the physical phone may not give investigators meaningful access to its contents.
The government has repeatedly encountered this problem in major investigations.
One highly publicized example followed the 2015 San Bernardino terrorist attack. The government sought an order requiring Apple to assist the FBI in gaining access to an iPhone used by one of the attackers.
That litigation ended without a definitive court resolution after the government reported that assistance from a third party allowed investigators to access the device without Apple's help.
The episode illustrated a larger reality:
Sometimes the government can lawfully possess a phone and still be unable to read what is inside it.
Compelling the Owner Is Not the Only Way Into a Phone
When investigators cannot unlock a device, they may have alternatives.
Forensic tools may exploit technical vulnerabilities.
Information may exist in cloud accounts.
Copies of communications may exist on another person's device.
A service provider may possess responsive records.
Backups may exist elsewhere.
Investigators may obtain evidence from computers synchronized with the phone.
The phone may therefore be only one location where the information exists.
This is particularly important with communications.
Deleting or encrypting one copy of a message does not necessarily eliminate the recipient's copy or records stored elsewhere.
The Government's Knowledge Before Compulsion Can Matter
Imagine two cases.
In the first, police find an unidentified locked phone in a shared house and order one resident to unlock it.
They do not know who owns it.
They do not know whether the resident has ever used it.
They do not know what is inside.
In the second, police watched a suspect use a particular phone repeatedly, seized it from his hand, and already possess independent evidence establishing his control over the device.
An order to unlock the phone may communicate more new information in the first situation than in the second.
That is why the government's knowledge before compelling an act can become so important.
The constitutional dispute is not always simply about the mechanical act of pressing a finger or entering numbers.
It can be about what that act communicates.
Unlocking the Phone Does Not Necessarily Admit Ownership of Everything Inside
There is another important distinction.
Knowing how to unlock a phone does not necessarily establish authorship or ownership of every file on it.
Multiple people can know a passcode.
A device can contain messages received from others.
Files can be downloaded automatically.
Cloud accounts can synchronize information.
Applications can generate records without deliberate action by the user.
A phone can be shared.
So even when investigators establish that someone can unlock a device, they may still need additional evidence connecting that person to particular communications, photographs or files.
Access and authorship are separate questions.
The Law Can Depend on Where the Case Is Being Heard
This is one area where overly simple statements are especially dangerous.
“Police can force you to unlock your phone.”
“Police can never force you to unlock your phone.”
Neither is a reliable nationwide summary.
Federal and state courts have confronted different facts and reached different conclusions about compelled decryption, passcodes and biometric unlocking.
Some courts have focused heavily on whether the compelled act is testimonial.
Others have analyzed whether any testimonial aspect is a foregone conclusion.
Biometric unlocking has generated additional disagreement.
As of September 2026, these issues remain active enough that petitions involving modern device-access questions continue to reach the Supreme Court's docket, underscoring that lower-court doctrine is still developing.
That makes jurisdiction particularly important.
The Technology Keeps Changing Faster Than the Analogies
Courts often explain compelled unlocking using old physical-world comparisons.
A key.
A safe combination.
A locked box.
A filing cabinet.
Those analogies are useful, but smartphones increasingly strain them.
A physical key does not usually reveal years of conversations.
A filing cabinet does not continuously synchronize with computers around the world.
A safe does not recognize its owner's face.
A locked box does not automatically change its security rules because it has not been opened for several hours.
Phones do all sorts of things that traditional containers never did.
And as authentication technology changes, courts will continue applying old constitutional principles to new forms of access.
A Few Digits Can Stand Between the Government and Years of Someone's Life
The remarkable part of the compelled-unlocking debate is how much can depend on such a small act.
Typing six numbers.
Touching a sensor.
Looking at a camera.
Those actions can take less than a second.
But what happens afterward may expose years of information.
That is why the constitutional issue is not merely about whether pressing a finger against glass is physically difficult or whether entering a passcode takes much effort.
The deeper question is what the government is compelling the person to communicate or enable—and whether the Constitution permits that compulsion under the particular circumstances.
A warrant can answer one question:
May the government search this phone?
It does not always answer another:
Can the government make you unlock it?
For modern courts, those can be two very different questions.