Keep asking the question again and again, but phrasing it differently. It's much more like an interrogation. Save the hardest questions till the end. Don't argue with your subject. Don't interrupt except to ask for more details.
Liars often give details.
You can later reconstruct their story step by step. If a person is a victim, be sympathetic without offering advice. You have to be fair. Once you establish intimacy and trust, you don't have to ask many questions. Break up long questions into parts.