Courts care about precise distinctions of law (that's their purpose!). Seems clear that fingerprints aren't protected, basically the same thing as your face in terms of privacy given a good enough camera.
But they would effectively be asking you the question "which finger did you use to lock this phone" to which you may plead the 5th.
But they would effectively be asking you the question "which finger did you use to lock this phone" to which you may plead the 5th.