As a matter of fact, I daresay the film covers every major aspect of a crime spree such as this one: the effect on the investigators' personal lives, the media coverage ("Dirty Harry" was directly inspired by Zodiac), the nutcases who come out of the woodworks, the copycats, the procession of false leads and near-arrests, the politics, the paperwork, the red tape, and the paranoia.
Toschi was supposedly the inspiration for the characters played by Steve McQueen in "Bullitt" and Clint Eastwood in "Dirty Harry."
As Inspector Dave Toschi, the SFPD detective who has inspired the characters behind three career-making turns (Clint Eastwood in Dirty Harry, which was loosely based on the Zodiac case, Steve McQueen in Bullitt and Michael Douglas in the TV series The Streets of San Francisco), Mark Ruffalo captures the vocal rasp and gruff energy of a homicide cop with an antithetical jones for kids' snack foods.
Mr. Toschi's unique way of wearing his holster provided the inspiration for Steve McQueen in "Bullitt"; The serial killer Scorpio from the first "Dirty Harry" movie was modeled on Zodiac; Brian Cox's character, Melvin Belli, appeared in the "And the Children Shall Lead" episode of the original "Star Trek" series.
To a point, that’s intentional: Zodiac was never caught, and Fincher aims to creep you out with the lack of closure, with the absence of a Dirty Harry?style climax and windup (Dirty Harry being one of the myriad serial-killer thrillers that drew its inspiration?if…
One of the film�s best scenes is a special screening of Dirty Harry held for the SFPD and just as Fincher shows us the obvious parallel between Zodiac and that film�s villain, he then trusts us with our knowledge of the film and the Zodiac's threats by using only the audio to creepily typify entertainment�s �ripped from the headlines� mentality.