But, as Schrodinger says, this is not about your fingerprint; it is about a bit of information you have that the government does not have: which of your finger(s) this device knows about.
"A bit of information you have that the government does not have" is a password.
I really don't understand this line of thinking. What is the scenario you imagine where the question of "which finger?" is relevant? I'll lay out the beginning:
- Police want to get into your phone for some reason
- You refuse to help them based on 5th Amendment or admiralty law or whatever
- They go to court for a order compelling you to operate the touch lock to open the phone
- You receive the order
- ?
Please lay out the "?" part, if you don't mind. I'm highly curious.
"A bit of information you have that the government does not have" is a password.