After her mother died, Johnisha Matthews Levi was sorting through boxes of ordinary family artifacts. There among the Polaroids, diplomas, and property deeds, she found a piece of paper that forever changed how she saw her family's story. Levi is an author and a former litigation attorney. While she was in law school, she helped represent death row inmates pursuing appeals and indigent defendants accused of murder. After finding that life-changing document in her mother's things, Levi channel...