I always switch off the biometric access of any machine, so you can save yourself the hassle of cutting off my thumb or trying to unlock a device when I am asleep.
I guess you could hope for their decency to cut off bits only after they've killed you. Combine that with their possible (probable?) stupidity to assume you have biometrics enabled, and they might kill you without even asking for any password, so you'd die secure in the knowledge that they'll never crack your data.