Never reveal how much you know before learning how much they’re willing to admit.

Once someone knows how much you have worked out, they can tailor what they tell you to fit it. Every disclosure you make sets the boundaries of their story, and an honest person will not need that help while a dishonest one will use it. Asking first is not a trick. It simply gives you an account that was not shaped around your knowledge.

When you already know part of the answer, ask open questions anyway and let them speak first. Compare what you hear with what you knew. The difference is usually the most useful thing in the conversation.