The Marshall says, he was shot in the back.
How could he be shot in the back if they both were facing each other ? That question was never raised.
Mark recreates the events leading up to the shooting, and pantomimes a rifle being used. Lucas then interrupts the court proceedings to declare a rifle had been fired from the Hotel window. The origin of the shot could be a reasonable guess, but no one would have known it was a rifle.
Lucas runs into the courtroom to say he has a negative of a man with a rifle shooting from the hotel window. BUT, at the end of the trial, Lucas claims he NEVER developed the negative. So, how did he know there was a shooter with a rifle in the window.