All-male juries?
I was surprised to see that, in the trial scenes in this movie, all the jurors were men. I would have expected to see women on a U.S. jury in 1932, considering that we had gotten the right to vote 12 years earlier. So I did some online research, and found that women didn't begin serving on juries in New York State (where the movie takes place) until 1937. It's amazing what you can learn from watching old movies.
Another bit of social history that tickled me came in the scene where Helen Vinson is waiting for William Powell in his office, and she picks up a magazine. We get a brief glimpse of the cover of the magazine, and it's clearly The New Yorker (that distinctive lettering is still recognizable more than 80 years later). A nice touch: it was just the sort of magazine an up-and-coming lawyer would have kept in his office for clients to look at, in 1932.