In 1991, Troy Davis was convicted of the murder of Savannah police office Mark MacPhail and sentenced to death. The state of Georgia executed Davis in 2011 amid public debate over his guilt or innocence. A new radio drama based on a 2016 play explores the meaning of "reasonable doubt" in the Davis case. We spoke with Lee Nowell, the playwright of "Beyond Reasonable Doubt: The Troy Davis Project," about the play's origins and its new life as a podcast on GPB .