After enough searches, one question has done more to predict a one-year outcome than any competency framework. What did you expect this role to be based on the JD, and what do you think it'll actually be once you're three months in?
Candidates who've done their homework give a specific, sometimes uncomfortable answer: a gap they've noticed, a question they still need answered. Candidates who haven't give an enthusiastic version of the job description right back to you.
The specific answer is the good sign. It means they're joining with their eyes open, which is the single biggest predictor I've seen of whether someone is still there in month thirteen.