Gareth Sewell Penn (born January 1, 1941) is an American true crime author and amateur detective known for being among the first non-journalists to write about the Zodiac Killer case.
Reviewing the 2007 David Fincher film Zodiac for the Las Vegas Weekly, Mike D'Angelo wrote, "I think the movie erred in selecting author Robert Graysmith as its source and nominal protagonist.
[4] Gareth Penn started writing about the Zodiac case in a 1981 article for California Magazine entitled Portrait of the Artist as a Mass Murderer.
[5] In Portrait, Penn theorized that the Zodiac crime scenes were selected by the killer in order to create a geometric shape over the surface of the San Francisco Bay Area as a sort of "murderous art project."
Part of Penn's commentary about that theory included the observation that, "Other artists had sought to remove their work from the ordinary human perspective.
According to FBI memos, an agent "contacted Penn by telephone and told him that if he was responsible for the correspondence to [O'Hare] he should immediately cease and desist, pointing out that it could jeopardize any investigation and he could possibly be subject to both civil and criminal penalties.