I don't see a solution for this. What you're describing is someone who's clearly good enough to take a project and rewrite it, and still be able to talk in deta

I don't see a solution for this. What you're describing is someone who's clearly good enough to take a project and rewrite it, and still be able to talk in detail about the code. I'd bet they could also pass a whiteboard, pair-programming or take-home test too. That they are willing to lie about it and pass off other's work as their own isn't something that you're going to identify in your typical code interview. Using interrogation tactics to try and weed out the frauds is going to be counter-productive, by driving off all the good candidates.