not if they charged it? wouldnt it last forever?

Don't think of Touch ID as unlocking the phone.

You know how you can "sudo" and type your password (if you have an account with sudo privileges) and then for a few minutes afterward you don't have to type your password when you use sudo?

Think of Touch ID like that: the passcode is still the thing that unlocks the phone, but once it's been entered you can use Touch ID for a little while, in much the same way that sudo can remember you've recently proved yourself to it. After 48 hours, after a certain number of failed Touch ID attempts, or after any restart of the phone, though, Touch ID stops being available and the phone goes back to only being unlockable via the passcode (Touch ID will only become available after the next time the passcode is entered).

that is what i am asking, where is the 48 hour part. ive never left my phone untouched for 48 hours, except in a powered off state.

Everything you ever wanted to know about iOS security (and a few things you didn't know you wanted to know): https://www.apple.com/business/docs/iOS_Security_Guide.pdf

You don't have to leave the phone untouched for 48 hours. Even if you touch it you still need the passcode every 48 hours. TouchID only works for 48 hours past the last passcode login.

Not quite, the passcode is needed 48 hours past the last unlock but the clock restarts with every login or unlock including TouchID unlocks.

Just as a point of reference, Android has a feature by which you can register locations at which a PIN is not required. I've registered my home (which is not super secure, since GPS resolution means it works anywhere in my apartment building), and I have to input the PIN every morning because the interval resets every 4 hours.

Where is that feature?

It's called Smart Lock: https://support.google.com/nexus/answer/6093922?hl=en

basch what happens is, at a minimum, the iPhone requires your PIN or passcode every 48 hours to unlock. In between, you can use your finger as many times as you want. So the 48 hour timer should fire as soon as immediately after someone gets posession of your phone, but no more than 48 hours afterward.

that is not true, I dont type my pin in every 2 days.

from what I read, the device has to be left in a locked state for 48h.

Contempt is only supposed to be for when someone's action brings the mechanism of a trial to a halt. Refusing to do an action that the court thinks it's allowed to compel you to do is an example.

Say she waits two days. The phone won't be unlocked with a fingerprint now; it requires a passcode, and the court can't compel someone to provide a passcode in the same way that it can compel them to provide fingerprints.

Contempt wouldn't be a valid charge anymore, at that point. If the judge won't recognize that, the prisoner/suspect could appeal.

The above is my understanding of the theory of how it works. Maybe I'm wrong. Maybe it works differently in practice.

Probably a ridiculous thought experiment, but I know folks have done similar things before, what if she cut off her thumb and disposed of it in such a way that it was irretrievable? Or something less permanent like dipping her thumb in acid to destroy the fingerprint surface - which would take weeks to heal. Would would the court do then?

It sounds to me like fingerprint authentication is not something a criminal should use if they don't want to get caught. Apparently a passcode is protected under the Fifth Amendment but not a fingerprint. [1]

But it's ridiculous really. All that a criminal needs to do is restart their phone to prevent their fingerprint from being used. And there are good reasons for doing so other than to escape incrimination! And that can be done from the lock screen... Imagine the criminal held down the power off button for three seconds then swiped, is that a crime? Perhaps that falls under spoliation of evidence, but then again how is not giving a passcode not considered spoliation?

Apple should require a user configurable timeout for requiring of a passcode. I'm sure it normally takes more than two hours to interview and charge someone.

1. http://www.macrumors.com/2014/10/31/fingerprints-not-protect...

> what if she cut off her thumb and disposed of it in such a way that it was irretrievable?

A contempt charge wouldn't hold any more (probably), but there's probably another charge that would apply, like spoliation of evidence [sorry, realized that you mentioned that charge further down in your comment].

> It sounds to me like fingerprint authentication is not something a criminal should use if they don't want to get caught.

True.

> Imagine the criminal held down the power off button for three seconds then swiped, is that a crime?

It's also not normally a crime for her to mutilate her thumb or for me to wave a knife around if I believe I'm alone and don't intend to harm anyone. Motive and context matter.

> but then again how is not giving a passcode not considered spoliation?

The act of making the fingerprint unusable would be the spoliation, I suppose. Not giving the passcode would be protected under the 5th.

>what if she cut off her thumb and disposed of it in such a way that it was irretrievable? Or something less permanent like dipping her thumb in acid to destroy the fingerprint surface

Sounds like intent to harm oneself, which gets one locked up in the loony bin until one demonstrates oneself to be of sound mind.

Not necessarily, thank goodness!

Sounds like obstruction of justice.

As often happens, I've heard of this term but had to look it up. I think you are right, that is obstructing justice.

The iPhone requires a password after a couple days of inattention, and does not accept Touch ID logins.