Minnesota Supreme Court Says Unlocking A Phone With A Fingerprint Isn't A Fifth Amendment Issue

from the non-testimonial-act-of-producing-evidence-against-yourself dept

When it comes to the Fifth Amendment, you’re better off with a password or PIN securing your device, rather than your fingerprint. Cellphone manufacturers introduced fingerprint readers in an effort to protect users from thieves or other unauthorized access. But it does nothing at all to prevent law enforcement from using their fingerprints to unlock seized devices.

The US Supreme Court hasn’t seen a case involving compelled production of fingerprints land on its desk yet and there’s very little in the way of federal court decisions to provide guidance. What we have to work with is scattered state court decisions and the implicit understanding that no matter how judges rule, a refusal to turn over a fingerprint or a password is little more than a way to add years to an eventual sentence.

The Minnesota Supreme Court has issued the final word on fingerprints and the Fifth Amendment for state residents. In upholding the appeals court ruling, the Supreme Court says a fingerprint isn’t testimonial, even if it results in the production of evidence used against the defendant. (h/t FourthAmendment.com)

From the ruling [PDF]:

Although the Supreme Court’s distinction between the testimonial act of producing documents as evidence and the nontestimonial act of producing the body as evidence is helpful to our analysis, the act here—providing the police a fingerprint to unlock a cellphone—does not fit neatly into either category. Unlike the acts of standing in a lineup or providing a blood, voice, or handwriting sample, providing a fingerprint to unlock a cellphone both exhibits the body (the fingerprint) and produces documents (the contents of the cellphone). Providing a fingerprint gives the government access to the phone’s contents that it did not already have, and the act of unlocking the cellphone communicates some degree of possession, control, and authentication of the cellphone’s contents. See Hubbell, 530 U.S. at 36. But producing a fingerprint to unlock a phone, unlike the act of producing documents, is a display of the physical characteristics of the body, not of the mind, to the police. See Schmerber, 384 U.S. at 763.

Because we conclude that producing a fingerprint is more like exhibiting the body than producing documents, we hold that providing a fingerprint to unlock a cellphone is not a testimonial communication under the Fifth Amendment.

The ruling notes the defendant did try to holdout on this, sticking to his Fifth Amendment arguments. But when the trial court gives you only unpalatable options, defendants tend to give prosecutors what they want.

The district court concluded that compelling Diamond’s fingerprint would not violate his Fifth Amendment privilege because “[c]ompelling the production of [Diamond’s] fingerprint or thumbprint would not call upon the use of [his] mind. It is more akin to providing a key to a lockbox.” Accordingly, it ordered Diamond to “provide a fingerprint or thumbprint as deemed necessary by the Chaska Police Department to unlock his seized cell phone.”

Diamond continued to object to providing the necessary fingerprint for unlocking the phone. Nevertheless, he finally unlocked the cellphone with his fingerprint in court after being held in civil contempt and warned of the possibility and consequences of criminal contempt.

This is an aspect never discussed by the FBI and others engaged in the war on encryption. Many, many people can be motivated to unlock devices when faced with the prospect of indefinite imprisonment on contempt charges. It’s something that should work in all but the most extreme criminal cases where the potential imprisonment might be as close to indefinite as humanly possible.

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Comments on “Minnesota Supreme Court Says Unlocking A Phone With A Fingerprint Isn't A Fifth Amendment Issue”

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Anonymous Coward says:


“Cellphone manufacturers introduced fingerprint readers in an effort to protect users from thieves or other unauthorized access.”

Is that true though?

I always assumed they introduced fingerprint readers for convenience – because they’re generally less secure if anything.

The only way they can add security is if you couple them with a pin/password as two-factor authentication.

Anonymous Coward says:

Re: um...

It depends. If you use a 4 number code to unlock AND you do not have the phone set to erase after “x” failed attempts, then a fingerprint reader is more secure. In that scenario, a criminal could fairly easily type in all possible codes by hand. Since this was (and maybe still is?) the default security setting for phones, then the fingerprint reader is more secure.

Additionally, security is not just based on theoretical security of the system, but also practical usage of said system. So if adding fingerprint readers (which are generally more convenient than a passcode) cause additional people to use security (e.g. people did not use a passcode because it was inconvenient, but do use a fingerprint), then adding the fingerprint did serve to increase the security of users. Good security is better than no security, after all, even if it’s not quite as good as it theoretically could be.

Anonmylous says:


So, how would Your Honor feel about, say, a dickprint? Taintprint? Anus scan maybe? I mean, they’re just parts of your body, right? No 4th Amendment violations cause they’re physical keys!

Do we REALLY want to go down this road of trying to decide which parts of the body are considered private and inviolate under the Constitution?

Roger Strong (profile) says:

Re: Riiiiiiight

Nipples are said to be as unique as fingerprints.

Most people keep those covered, so they should be secure. We can use the same readers built into phones.

The icons may have to change, but I’ll leave that to others. Having read that “the only truly intuitive user interface is the nipple,” I’m not allowed to work on UI design any more.

Let’s reserve your alternatives for two-factor authentication.

Anonymous Coward says:

Re: Re: Riiiiiiight

Anything that is covered will be uncovered when the state demands it. Such is the nature of the state.

Remember this, because when they finally can read your thoughts with a computer, nothing will qualify as “being compelled” under the fifth ammendment. As “being compelled” by them, requires your ability to deny them.

nasch (profile) says:

Re: Riiiiiiight

Do we REALLY want to go down this road of trying to decide which parts of the body are considered private and inviolate under the Constitution?

I don’t think this decision hinges on whether a finger is public. It just states that presenting the body is not a 5th amendment issue. It mentions blood samples, and your blood is even more concealed than your taint.

Arthur Moore (profile) says:

Re: Killswitch

My current phone (Moto G5 Plus) requires a password every 72? hours. That’s pretty secure. Also, simply being able to lower that number to say 24 hours would help tremendously.

It also has the (now standard) 10 bad tries and wipes the phone feature.

A consequence of all these actions are that phone manufacturers are actively working on ways of making the devices more secure against coercion.

Here’s another good idea. I have a smart watch, what if every time the phone looses connection to it for a few minutes it requires a password. That’s something that’s easily doable, and would mean that any time I’m separated from my phone it goes into a more secure state.

nasch (profile) says:

Re: proof

Don’t they need some indication the phone was used for the crime, other than "phones have everything"

I think in theory they would need probable cause to think there is evidence of a crime on the phone, not that the phone was used to commit a crime. In practice I suspect judges are pretty lenient in assuming phones have useful evidence on them.

Roger Strong (profile) says:

Re: Public service announcement: press the iPhone power button 5 times on any encounter with police, TSA, ICE

Public service announcement: The obstruction of justice statute states that it’s a felony to alter, damage or remove something so it can’t be used as evidence in an investigation or proceeding.

If "fingerprint disabled" is your phone’s normal state, that may be OK. Disabling it on the fly when the police ask you to unlock it may be a felony.

ANON says:


Yes and no. Recall a case back in the phone hacker days, when a prisoner was left alone with his autodialer in an interrogation room. He removed the batteries, and the device “forgot” all its programming. He was convicted of obstruction for destroying evidence.

Now, simply changing the security of your phone (not wiping it) ma or may not be obstruction. It seems to me to be textbook obstruction – you have made it more difficult for the police to obtain the necessary(?) evidence, but you have not destroyed evidence.

However, the court decision is what people have been saying for years. Producing your fingerprint is something you cannot refuse to do, everyone who is arrested does so. Whether it identifies you and goes into a database, or whether it unlocks a phone, you still have to give police the finger.

IIRC the iPhone will require the passcode after 48 hours of being locked or a reboot. So the trick is to stall long enough…

maybe a future enhancement would be to require the passcode to allow charging… 🙂

That One Guy (profile) says:

This is why we can't have nice things

Apple rolls out a feature designed to provide a measure of security while also being fairly easy to use.

Police/courts take note that the ‘password’ involves a body part rather than knowledge.

Police argue, and courts agree, that while the end result is the same, compelling someone to unlock a device with a fingerprint rather than a password is acceptable, such that police now have a dodge around the fifth so long as the accused has one of the relevant devices.

End result: A feature that was designed to protect the privacy and data of the owner is now being used against them.

Discuss It (profile) says:

I actually sort of agree with this.

A fingerprint is something you are. It’s content neutral. What I don’t agree with is forcing someone to give up their pin/password, that’s something you know.

The 5th provides we cannot be compelled to testify against ourselves – because that is something we know. Like a pin/password.

If you can be forced to give up something you know like a pin/password, then it’s just a short step to “guilty until proven innocent”. Which, some to think of it, is pretty much the system we have now. Note 1

Crimes were solved way before we had self paid ear tags that our smartphones essentially are. Solve crime the old fashioned way – work for it.

1. A friend of mine had his checkbook stolen, which was reported to the police. 4 months later, he’s arrested for passing bad checks. Upon review of the evidence against him, it was found a fat, short, white man was photographed passing the checks. My friend is a tall, slender black man.
Didn’t matter to the DA. He had a set of plea deals set up to send my friend to jail for 14 years, and was going to press ahead. The judge, however, looked at the evidence, and invited the DA to “reconsider in light of the evidence, police reports, rule 11b, and the court’s extreme displeasure.” I will add that my friend is possibly one of the smartest people I’ve every met, holds over two dozen patents (none of which are BS), and earns more money than you can shake a stick at. Had he been poor and unable to afford a good attorney, I’m sure this would have had a different ending.

ANON says:

Re: I actually sort of agree with this.

This is a side-effect of electing DA’s. When the criteria for hiring is “ability to schmooze and be slimy” rather than legal competence, and being able to tout success stats is what gets you re-elected, any surprise that cream isn’t the only thing that floats?

Canada appoints crown attorneys and of all the systemic complaints, stupidity and blind determination to improve conviction stats are not part of the problem.

Paul Brinker (profile) says:

Re: I actually sort of agree with this.

You forgot something, the cops can force me to put my finger on the scanner, but they have to choose which finger and I forgot to tell them I am left handed.

This is now an issue of knowledge and not an issue of body part and I have no intent of telling them which finger to use, only that I will place any finger they want on the scanner.

Games yes, but if they are going to argue producing the finger is fine, I can ask what finger and they can’t just say “The Correct One” as now I am providing information.

That One Guy (profile) says:

Re: Re: I actually sort of agree with this.

Not a problem(for them anyway), unless the phone locks up after a certain number of failed scans, and that number is lower than ten, they can simply demand that you try with every single finger until the correct one.

Mind, assuming it does lock up and the number is lower than ten that might be a passable argument, though how well it would fly in court would really be up to the judge involved.

ANON says:

Re: Huh?

If you have the password written down, and this FACT is known to the prosecution, they can serve you with a warrant to produce said document. You cannot refuse. (Only exception AFAIK is communications between client and lawyer). If you destroy it, that is destroying evidence.

If they do not know there is such a document, then they cannot ask for it with a warrant. that would be a fishing expedition.

but having things in writing is a really(!) bad idea.

Bob says:

This is a really simple discussion.

Gathering evidence with biometric authentication is a search of a person. Your fingerprints have never, in the past, been covered under 5th amendment and this isn’t either; whether it’s a physical key or your hand is no different. You do not put a person in peril of being in jail forever due to being unwilling to produce a finger; you can compel them by force if needed. This is a 4th amendment discussion which the police and courts would prefer to avoid as you need a written warrant and chain of custody on the evidence for it to be admissible. That is a real problem for routine “traffic stop” or “stop and frisk” searches because we already have precedent that searching a phone is an evidence-fishing exercise. Furthermore, forensics on a phone is a major PITB because the data lives in all sorts of places that are hard to reach and may require additional warrants; chain of custody on cloud data is a real problem.

Things like reactions, lie detectors, knowledge, and skills are all protected by the 5th amendment.

tom (profile) says:

If I have modified fingerprint security on a phone such that a left index finger unlocks and a right index finger encrypts with a random key, is the decision of which finger to provide ‘Testimony’ in the courts opinion?

Part of this ruling was that providing a finger didn’t require “The use of his mind”. Having to decide which finger to use would require “use of mind”.

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