I don't know the verbatim message, but it says something along the lines of "Passcode is required to enable Touch ID"
Edit: with Touch ID enabled, if you slide to the lock screen without touching the sensor, it says "iPhone requires your passcode after restarting" but the title says "Touch ID or Enter Passcode"
Difficult to prove.
Any muppet attorney can come up with a hundred reasons why this was a perfectly reasonable thing to do.
I think you could just argue that you didn't want the disturbed and/or wanted to save some battery.
No. The difference is that the action is taken to obstruct a specific investigation. Generally protecting information without regard to a specific investigation is not obstruction. Same as shredding papers years before they become relevant to an investigation is also not obstruction.
> I think you could just argue that you didn't want the disturbed and/or wanted to save some battery.
Like perjury, proving obstruction may be difficult. That doesn't make it any less illegal.