Yeah, you could just ask questions that you wanted to know the answers to, then go off vibes, or you could write a list of questions that only you and the person knew the answers to, and have someone else ask them, write the answers and bring them back to you.
But I thought Doppelgangers could Read Thoughts?
Who's to say they don't know all the facts the victim does/did?
Although the last panel is clever, that could work on a constructed Doppelganger!
Yeah, you could just ask questions that you wanted to know the answers to, then go off vibes, or you could write a list of questions that only you and the person knew the answers to, and have someone else ask them, write the answers and bring them back to you.