The so-called “Zodiac hoax theory” claims that the “Zodiac killer” never existed and that the many Zodiac messages were part of a hoax perpetrated by members of law enforcement and/or various other individuals. These claims are based on an interpretation of official documents, speculation, assumptions, and a vivid imagination. Citing discrepancies, factual errors and other issues in official documents, the hoax theory offers a narrative which may seem compelling to some observers but the facts tell a very different story.
Much of the hoax theory seems to depend on an illogical premise that the Zodiac, if he actually existed, must have been truthful and accurate in his letters. If he was not accurate or truthful, this is not evidence that he was inaccurate or untruthful— it somehow magically becomes evidence that he did not exist at all. This premise is not the product of a logical progression or inference. The fact that the Zodiac letters may contain factual errors, falsehoods, inaccuracies, and unsubstantiated claims does not constitute evidence that the author was not responsible for the murders. The fact that some Zodiac letters may contain information which was also available from other sources does not prove that the Zodiac letters were part of a hoax.
Murderers are people, and some people are honest while others are dishonest. If someone looks at the Zodiac letters and believes that the writer was wrong about some detail, that is not evidence that the letters were a hoax simply because someone cannot reconcile some set of facts or bits of information. The writer may have had a reason to lie, or, the writer may have made a mistake. Either scenario is more logical than the hoax explanation. A serial killer attempting to avoid capture and mislead authorities would most likely have many reasons to be dishonest, and anyone who committed the act of murder at night in a matter of minutes would undoubtedly be mistaken on some accounts when attempting to accurately recall the events at a later time. The first Zodiac letters arrived more than seven months after the murders on Lake Herman Road and more than three weeks after the shooting at Blue Rock Springs Park. Given the passage of time, the killer would most likely make some mistakes unless he took meticulous notes and photographs at the crime scenes.
The evidence demonstrates that the most logical, plausible and likely explanation is that one individual was responsible for the crimes and the letters. Reasonable doubts regarding the authenticity of some letters attributed to the Zodiac and the alleged connection between the crimes should be based on credible evidence and reality.