When they don't know who they are and what they want out of life. A candidate knows the interview isn't going well when they find my interview questions novel, meaning they haven't thought about these questions before. In reality, I'm just trying to get to know them, but they don't know themselves, so the questions make them very uncomfortable. Candidates typically get the picture virtually immediately, though, since I simply communicate to them that the fact that they don't know the answers to the fundamental questions I ask them poses a serious risk to everyone on the team. Self-awareness is key to quality team membership for us. While that may sound brutal, interviewees most often really appreciate the transparent approach we take to the process. TGNTIY.