Pentuple clicking of the side button disables biometric ID. Going to the power menu by holding volume and side button does the same.
I don't have an iPhone with FaceID to test this, but supposedly you need to be looking at the phone as well, so it should be fairly easy to avoid unlocking the phone under duress (consequences notwithstanding).
Disclaimer: I don't use biometrics anywhere
I don't have an iPhone with FaceID to test this, but supposedly you need to be looking at the phone as well, so it should be fairly easy to avoid unlocking the phone under duress (consequences notwithstanding).