I am tasked with interviewing a candidate about a technical skill that I am not an expert in. What would be a good way to prepare for this interview (i.e how do I choose what questions to ask)? Should I just read up on the technical subject and formulate my own questions? Or just search for similar questions people have asked in the past?
Ask them to explain in detail a technique. Ask them to cover how it works, why it works, what are the mathematical foundations (or underlying tech, or principle foundations, as applicable). You can frame it as "as if I knew nothing about the field".
It is a good technique, because you get to probe communication skills. It is also useful, if you happen to actually know nothing (or not much) about the field. It also allows you to ask about stuff you know in-depth and verify how far they're trying to string you along.
You can even feedback with: "So, if I understand correctly ...." and keep digging. It should allow you to distinguish between:
- rote learners that just name-drop stuff
- people who understand stuff and can actually explain it
- fakes that just throw random stuff around hoping you won't see through