Since we live in the real world, even on a technical site real-world scenarios feel more common-sense (and less likely to be mistagged in the future).
So, if I were looking for an appropriate tag, I'd feel that "fingerprint" (being a common term amongst non-technical people) is more intuitive than "biometric". For example, many laptops and phones now come with a "fingerprint reader", and far less often marketed as a "biometric device" (although I have seen it once or twice when selling security systems in particular).
I'd therefore argue that dividing it into:
would be more likely to guide taggers to the right tag.
In general, I'd say "concept-industry" would be a good tag scheme in this case, however I also see that there's an overlap. For example, understanding the cryptography in fingerprint readers (to prevent MITM attacks) would fall under either (or both) tags. So there isn't a perfect answer here.