Factual error: In a couple of scenes, most notably the one where Graysmith drives his kid to school, there are newer cars in the background than the year it is supposed to be. In this scene the car is a 1971 Chrysler, when the scene takes place in 1969.
Continuity mistake: In the scene where Graysmith goes to Vaughn's house, his jacket is soaked from the rain. Moments later he is sitting in a chair, and we can see his jacket is dry. Not enough time passed in the film for the jacket to dry.
"Suspect": I'm the Zodiac.
Inspector William Armstrong: And how did you kill your victims?
"Suspect": With a gun. No... with a hammer.
Question: There is a scene in Robert Graysmith's kitchen where you can see a container of Old Bay Seasoning on the top of the stove. I am from Maryland and I found it unusual that they would have it out in California, especially before the internet came into being. Did I see that wrong? I couldn't find the answer anywhere else.
Question: Near the end of the film a high school year book is shown. What school is it from and what year?