There is a very, very definite POD here.
Zodiac's 1969 murder of a cabbie was witnessed and a description given to police in the area. Unfortunately, the dispatcher somehow made a mistake (I hope it was not deliberate) when talking to officers and described the suspect as black when he was really white. So the cops literally walked right by him; later, when they heard the real description, they realized they'd seen him. In a letter, Zodiac confirmed they almost got him (and included a piece of the cabbie's bloody shirt as proof it was him).
Speaking as a dispatcher, it's one of the worst marks on our profession.
But let's say the dispatcher gets it right and Zodiac is arrested. What else would this change? Assuming he's a relative nobody, not a public figure.
I think Dirty Harry would be butterflied away or at least be significantly changed. Would "criminal mind games" in general be less popular in culture, since we don't have the mystique of the one who got away?