The Imdb page gives away who the Zodiac killer is, in the casting!
SPOILER
I don't know the true story, so I wanted to not read it, and just watch the movie, not knowing.
But in the IMDB page of the movie, in the cast, it gives away who the killer is buy naming the character with three names, Arthur Leigh Allen. In the U.S. the media and police often brand serial killers or murderers with all three of their names.
Lee Harvey Oswald, John Wilks Booth, James Earl Wray, Gary Leon Ridgway, John Wayne Gacy, etc.
So by the Imdb giving the character three names in the casting, they totally spoil who the killer is.
Maybe it was unintentional though.
What do you think?