Film - The Conspirator

From Gateway:

"The Conspirator" is the story of Mary Surratt (Robin Wright), the only woman charged as a co-conspirator in the killing of President Lincoln, and the mother of John Surratt, one of the eight conspirators that included John Wilkes Booth. The 28-year-old Fredrick Aiken is a Union solider who recently returned from the war and is just beginning to practice law. His mentor, Reverdy Johnson (Tom Wilkinson) asks him to take the case. He is reluctant at first but soon begins to see the injustices in Surratt's military tribunal.

This movie isn't just about the execution of Surratt. Though it plays like a legal thriller, you never get that David and Goliath feel. History has told us how this story ends, and it's fairly clear from almost the first courtroom scene that Aiken has no chance of winning.