I'm in the fortunate position of interviewing developers for the Identity team at Mozilla. I'm not sure how common it is for a designer to interview a developer, but that's how we do. I queried Twitter "Designers: When interviewing a developer for your team, what are your best questions for finding out if you'll work well together?" Here are the excellent responses.
I neglected to specify that of course, I'm not the only person interviewing developers. That would just be ludicrous. The majority of the people interviewing any given candidate will share the same skillset. Then a few others from the project team will ensure culture fit. Mozilla typically does two or three phone screens and approximately six in-person interviews.