But my phone is mine, it contains deeply personal things that I put on there without the intention of sharing them. How is forcing me to unlock my phone anything other than forcing me to testifying against myself?

If they could, they would read your mind too.

The analogy that's sometimes used is that of a safe full of documents. Current case law says that you can be compelled to turn over a key but cannot be compelled to turn over a password [1].

The Department of Justice is saying that a fingerprint is more like a key than a password I guess. Or alternatively that unlocking phones is search and not testimony.

The EFF seems to be primarily objecting on the grounds that a search of "all devices in the building" is too vague to be a correct warrant.

[1] http://www.uclalawreview.org/the-fifth-amendment-encryption-...

Couldn't you say the same about a safe on the premises being searched?

The self-incrimination clause of the fifth amendment is broadly interpreted as intended to dissuade the government from attempting to coerce confessions. Forcing someone to unlock their phone with a fingerprint caries none of the moral hazard of forcing them to testify.

All of that being said, I'd love for US society to recognize that a search encompassing a bunch of people's phones is vastly more intrusive (by virtue of the volume of data collected and network effects) than a search of a building that excludes computing devices, and for us to require a correspondingly higher burden of proof.

How about we stop expecting "justice" to work in our favour and start forcing it to work in our favour?

If you don't want anybody to be able to take your stuff, don't make it possible for somebody to take your stuff. A piece of paper saying something isn't permitted is not going to stop it happening.

If the piece of paper says I can be forced to tell them my password, they will try to force me... and I will give my password. You can simply put people in jail for not disclosing their password, when the law provides these means.

The fingerprint is not communicative. That's the crux of the matter. The state of law, currently, is that if the police have you, and they have your phone, and they have probable cause that your phone contains evidence of a crime, they can compel you to press fingers to the phone.

It's no different, really, then that they can force you to press your fingers onto a sheet of paper for booking during an arrest, or to take a buccal swab.

What they apparently cannot do is force you to admit what if any finger of your would unlock the phone. Apparently some people use tricks like locking the phone with a knuckle or even the tip of their nose (that one sounds comical). Really though, it goes to show that the good old fashioned memorized password has not gone out of style. Any biometric or dongle-based authentication or encryption can be circumvented by legal process.

And in a civil matter, judges and parties have even more power. Ultimately, if a court is convinced that you know a password and are not properly invoking a 5th amendment privilege against criminal self-incrimination, you could be held in contempt (fined daily, or jailed) until you provided the password or the password-protected materials. At this point it could well become a battle of wills and proofs, which the contemnor may well lose.

"If it's something you have, it can be taken off you"

yet this law was made for identification purposes, not unlocking safes.

Right, and considering fingerprint's long history as identification, it seems like it would be both impossible & unreasonable to try to split the two uses. Can we really say "You only obtained his fingerprint for the purpose of identifying him, you can't use it to unlock the phone"? And, we can't reasonably try to end the use of fingerprints as ID...

> Can we really say "You only obtained his fingerprint for the purpose of identifying him, you can't use it to unlock the phone"?

That seems to me to be a very reasonable thing to say. It seems to me that we have plenty of mechanism in place to say "you have X, you can use it for Y, and not Z, because using it for Z violates someone's rights". As a super contrived strawman example, if your computer ever gets confiscated by law enforcement, while they may be permitted to search it, they can't just play Fallout 4 or mine bitcoins on it.

Another instance I think is similar in concept: juries are instructed to disregard things (i.e. pretend they don't have a piece of information for the purposes of a trial) all the time, when access to this information would be improper.

To be clear I don't think it's unreasonable, it just seems it would be difficult to define & enforce, because it's already matter of public record. For example, what if the fingerprint was lifted from the scene of the crime? Can you use that to unlock the phone?

if your house key is laying outside, can they use it without a warrant?

Exactly, the fingerprints aren't material evidence in this case, but communicative testimony that could lead them to unspecified future material evidence on their phone. It's not the same thing at all.