Also: finger unlock only works after a password has been entered once (to generate the "finger unlock" key). Copying fingerprints or compelling finger access is moot if the device dumps the finger unlock key (as is done after 48 hours of no finger auth or after 5 (?) failed finger auth attempts).

But, trying to revoke the finger auth key in an emergency (less than 5 seconds) is difficult. Your only option is to try and quickly power off the device, but you're at the mercy of the "press and hold sleep/wake button for 5 seconds, then slide to turn off" delay timer.