UPSC evaluates the knowledge depth during interviews by asking candidates probing questions that require them to demonstrate comprehensive understanding and critical thinking. Candidates are often presented with current affairs, ethical scenarios, or personal experiences to gauge their analytical abilities and reasoning. The board observes not just the correctness of the answers but also how candidates handle complex topics, articulate their thoughts, and justify their positions. This evaluation method ensures candidates are well-rounded and capable of handling the responsibilities of civil service roles.