Which was the very 1st movie about...
... a trial?share
Apparently the first Amercian Film was made by an Italian by the name of Edwin S. Porter he is known as the “father of the story film.” He worked for Thomas Edison. He is mostly known for directing the first major American motion picture titled “The Great Train Robbery.” It was later known as the first western film.
Not sure if this is considered the first film though since the first things captured on film had no story they were just simple actions like watering the lawn and stuff.