Some lawyers routinely ask this question at expert depositions--
Q. "What is your understanding of your role in this litigation?"
Because the question can be answered in so many different ways, it functions as a sort of Rorschach test that will give you insight into an expert's manner of answering questions. Ask the question to ten different experts and you'll get ten different answers.
Usually you'll learn something useful. If experts are improperly prepared, they might ramble on about their relationship with the lawyer who hired them; you might learn something your opposing lawyer didn't intend the expert to reveal. If experts are inexperienced, the question might make them uncomfortable; you'll learn how the expert handles stress.