The story, based on true events, is set around the assassination of President Abraham Lincoln, with Wright Penn (Mary Surratt) playing the part of the only woman in a group charged with the conspiracy and McAvoy (Frederick Aiken) as a war hero who takes to defending her.
James Solomon wrote the script.
According to Variety, the film is set to start lensing in October, with financing from Joe Ricketts and his American Film Co., committed to filming American historical events and stories.
"Stories from our history are often more compelling than fiction," Ricketts said. "Mary Surratt's trial is a powerful, relevant story." The company has enlisted the help of historians and Lincoln assassination experts like James McPherson, Thomas Turner and Col. Fred Borch to help tell the tale.
Redford, who is also producing the effort with Greg Shapiro and Bill Holderman, last directed 2007's "Lions for Lambs." Wright Penn can currently be seein in "The Private Lives of Pippa Lee" while McAvoy is rumored to be committed to a "Wanted" sequel.