Motherboard:

But Face ID can of course also work against law enforcement—too many failed attempts with the ‘wrong’ face can force the iPhone to request a potentially harder to obtain passcode instead. Taking advantage of legal differences in how passcodes are protected, US law enforcement have forced people to unlock their devices with not just their face but their fingerprints too. But still, in a set of presentation slides obtained by Motherboard this week, one company specialising in mobile forensics is telling investigators not to even look at phones with Face ID, because they might accidentally trigger this mechanism.

We had passcodes, then fingerprints, then faces, the evolution of biometric mechanisms used to unlock you phone. Will this evolution continue? Or is Face ID the final stop?

No matter, this is a knotty problem on all sides. Protect privacy, but make it effortless to unlock a phone.