The man positioned as the most likely suspect in the Zodiac case by Fincher’s movie and Graysmith’s book is Arthur Leigh Allen. The extensive circumstantial evidence is shown in the movie, including his Zodiac brand watch which contained the symbol that appeared on each Zodiac letter. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.