If you program daily, but were nervous during an interview, I would have been able to tell and always tried to get candidates comfortable before getting into any programming - talking about something they liked or were passionate about, reframing my questions in terms of something we talked about or was on their resume.

I found most of the people who couldn’t program were not the nervous ones, but were smooth talkers who probably didn’t write much code. Maybe they did at one point, maybe they never did, it was hard to know, but I couldn’t get even logical steps to solve straight forward problems out of them. Those were the worst interviews, not because the candidate wasn’t a fit for the role, but because then I had to panic to try to keep the experience positive, constructive, and collaborative. When I expected to fill 20-40 minutes talking through a problem with someone who can’t solve problems, let alone produce anything remotely looking like code, I always found that painful.

The questions I asked could be solved by non-programmers (my wife, who was an elementary teacher and even my kindergarten son could come up with reasonable solutions, but of course not code). That was probably the biggest issue I ran into with nervous people - they didn’t think about the problem first, they’d try writing code before really thinking through. That was usually easy to correct and I didn’t fault anyone who could handle correction and guidance.