Can Police Force You to Unlock Your Phone in Minnesota?

The Core Rule: Biometrics vs. Passcodes

The Fifth Amendment protects you from being forced to be a witness against yourself. Courts have long held that this protection covers testimonial acts — things that reveal the contents of your mind — but not physical evidence taken from your body. That single idea drives the whole area of law:

• Passcodes and PINs are protected. Telling police your passcode means pulling a fact out of your memory and communicating it. Courts treat that as testimony, so the Fifth Amendment generally shields you from being forced to reveal it.
• Fingerprints and Face ID are generally not protected. Pressing your finger to a sensor or looking at your phone is treated like giving a blood sample, standing in a lineup, or being fingerprinted at booking — a physical act that does not require you to say anything or reveal what you know.

The classic way courts explain it: being forced to hand over a key to a safe is a physical act, but being forced to reveal the combination to that safe is testimony. Your fingerprint is the key. Your passcode is the combination.

What this means for you: The lock you choose on your phone can change your constitutional protection. This is the rare situation where a setting on your device, not a courtroom argument, decides the outcome.

Minnesota's Leading Case: State v. Diamond

Minnesota settled the fingerprint question early. In State v. Diamond (Minn. 2018), police lawfully seized a burglary suspect's cellphone and got a valid warrant to search it, but the phone was locked with a fingerprint scanner. When the suspect refused to unlock it, the district court ordered him to press his finger to the phone, and he did so only after being held in contempt.

The Minnesota Supreme Court held that there was no Fifth Amendment violation. Because providing a fingerprint produced only physical evidence and did not reveal the contents of his mind, the act was not testimonial. The court expressly compared it to furnishing a blood sample, giving handwriting or voice exemplars, standing in a lineup, or ordinary booking fingerprinting — all things courts have long allowed the government to compel.

State v. Diamond was a case of first impression when it was decided; at the time, no state supreme court and not the U.S. Supreme Court had ruled on compelled fingerprint unlocking. It remains the controlling rule in Minnesota state court today.

What this means for you: In a Minnesota state prosecution, if officers have a valid warrant for your phone and it is protected by a fingerprint or face lock, a judge can order you to unlock it — and refusing can expose you to contempt.

The Federal Courts Are Now Split

Here is where the picture has changed, and why the “biometrics are never protected” shorthand is no longer safe to rely on. Since Diamond, two federal appeals courts have reached opposite conclusions:

• Ninth Circuit — not protected. In United States v. Payne (9th Cir. 2024), officers forced a parolee's thumb onto his phone during a traffic stop. The court held this was not testimonial, reasoning that the physical act required no cognitive exertion — the person “said nothing” — and was more like a compelled fingerprinting or blood draw. This is the same reasoning Minnesota used in Diamond.
• D.C. Circuit — protected. In United States v. Brown (D.C. Cir. 2025), the court reached the opposite result, holding that compelling a thumbprint can be testimonial because the act itself communicates knowledge of ownership and the ability to access the device — functionally the same as being made to reveal a password.

Legal observers widely view this disagreement as a circuit split ripe for the U.S. Supreme Court, which has never directly decided the biometric-unlocking question. Until the Supreme Court or Congress steps in, whether a fingerprint or face scan is protected in federal court can depend on which circuit you are in.

What this means for you: The rule is not uniform nationwide. In Minnesota state court, Diamond controls and biometrics are compellable. In federal court, the answer is contested and jurisdiction-dependent. The one thing that stays constant everywhere: passcodes remain protected.

The “Foregone Conclusion” Wrinkle

Even the passcode protection is not absolute. Under the foregone conclusion doctrine, the Fifth Amendment does not shield you from revealing something the government can already prove it knows. If prosecutors can independently establish that a particular phone is yours and that you know how to unlock it, some courts have held that forcing you to do so reveals nothing new — and order it anyway. How and whether this doctrine applies to passcodes is itself heavily litigated and varies by court.

Does Miranda Help Here?

Miranda warnings apply to custodial interrogation — questioning designed to get you to talk. Being ordered to press a finger to a sensor or look at a phone under a warrant is treated as a physical act, not interrogation, so Miranda generally does not apply to it. That is another reason the fingerprint-versus-passcode line matters so much: your Miranda rights protect what you say, and a fingerprint is not something you say. For more on when questioning triggers these protections, see our page on Miranda rights and police questioning in Minnesota.

How to Actually Protect Your Phone

Given all of this, the practical advice is straightforward and works in every jurisdiction, because it does not depend on how the biometric question is ultimately resolved:

• Use a strong passcode or PIN as your primary lock — not just a fingerprint or Face ID. A passcode is the one credential courts uniformly treat as protected testimony.
• Know how to disable biometrics fast. Modern phones let you force a passcode-only state (for example, powering the device off, or triggering the lockdown/emergency setting), which disables fingerprint and face unlock until the passcode is entered. If a phone is powered off, it typically requires the passcode on restart.
• Understand that a warrant changes things. These protections concern what the government can compel from you. They do not stop police from lawfully seizing a phone, getting a warrant, and using forensic tools to try to get in on their own.
• Do not physically resist or destroy evidence. Asserting a constitutional objection is your right; obstructing officers or destroying a device is a separate crime. Object clearly, comply with a lawful court order if one is issued, and raise the legal challenge through your attorney.

What this means for you: If keeping the contents of your phone private matters to you, the concrete step is to rely on a passcode rather than biometrics as your real lock. It is the protection that holds up across Minnesota and federal courts alike.

How This Fits With Search-Warrant Law

The compelled-unlock question sits on top of a separate set of rules about when police can search a phone at all. Under Riley v. California (2014), officers generally need a warrant to search the contents of a phone seized during an arrest, and under Carpenter v. United States (2018), they generally need a warrant for your historical cell-site location data. So the sequence in a real case is usually: police seize the phone, obtain a warrant, and then — if the phone is locked — the compelled-unlock question arises. To understand the warrant step itself, see our pages on search warrants in Minnesota and digital and electronic search warrants. If police already searched your device, our page on suppressing illegally obtained evidence explains how a motion to suppress works.