Then came further handwriting experts claiming that the 1978 letter looked traced and too similar to previous correspondence. In the San Francisco Examiner on August 3rd 1978, four experts, Keith Woodward (head of Los Angeles documents department), John Shimoda (Postal Service crime laboratory), Robert Prouty (Chief documents section/Bureau of Criminal Identification and Investigation) and Terry Pasco (also Criminal Identification and Investigation), all deemed the 1978 letter a fake. Keith Woodward described the 1978 letter "a carefully drawn copy of the true Zodiac printing". He concluded it "was a poor attempt by an unknown writer". John Shimoda declared it "an attempt to duplicate Zodiac letters and is not authentic". Robert Prouty and Terry Pasco said basically the same thing.
The experts concluded that the 1978 was effectively a "copy", attempting to duplicate authentic Zodiac letters. So why would an obvious copycat duplicate the Melvin Belli letter introduction, when this was the only Zodiac communication up to April 24th 1978 that had the deviant introduction of "This is the Zodiac speaking I". If the author of the 1978 letter was attempting to imitate previous Zodiac communications so precisely, then why didn't he duplicate the introduction of "This is the Zodiac speaking" from at least four letters published in the newspapers?. This introduction was much more widely publicized.
The author of the April 24th 1978 "I am back with you" letter (if a hoaxer) had every opportunity to just mimic any one of these common introductions, yet he chose to mimic the Melvin Belli letter on December 20th 1969, which broke with tradition. The Melvin Belli message began with "This is the Zodiac speaking I", but was grammatically incorrect in failing to place a comma or full-stop between "speaking" and "I". Therefore, the author of the 1978 letter (if a hoaxer) chose to imitate the message on the opening line of the Melvin Belli letter (including the punctuation error) rather than the standard introduction used by the Zodiac Killer. One would have expected a Zodiac copycat to mimic any one of the four introductions available in the San Francisco Chronicle - but they didn't. The 1978 author mimicked the only one not publicly available in the Chronicle. Both letters also began with the author addressing the receiver by way of "Dear Melvin" and "Dear Editor". From August 4th 1969 to March 13th 1971, this "addressing of the receiver" within the letter was only performed twice (8/4/69 and 12/20/69). These observations may suggest the Zodiac Killer authored the 1978 letter after all. When you consider the same introduction present in the Melvin Belli and 1978 letter, was it just coincidence that the Melvin Belli letter stated "I can not remain in control for much longer", to which the 1978 letter replied with "I am now in control of all things"?
In late 2017 there was optimism regarding a new round of testing of the Zodiac letters. In early 2018, the Sacramento Bee reported that "Vallejo police Detective Terry Poyser, who has worked the Zodiac case for four years, said his agency has submitted two envelopes (in late 2017) that contained letters from the Zodiac Killer for a type of advanced DNA analysis that previously had not been available in the case. Poyser declined to identify the lab, but said it would attempt to obtain a full DNA profile from saliva on the envelope flap and stamps. He said he expected to have results back from the lab as soon as in the next few weeks, and almost certainly by summer". But according to the above sources and the "DNA Sample Obtained" comment by the San Francisco Police Department laboratory, we already have a DNA sample from the 1978 letter. Therefore, with little doubt, we have DNA from the Zodiac Killer - and have done for many years. This DNA from the 1978 letter should now be run through the genealogy database to generate fresh information in this long-standing case. If Alan Keel is correct, then we definitively have a full DNA profile of the Zodiac Killer from the 1978 letter, that he claimed matched one of the 1974 letters (which could very well be the Exorcist letter, as this was the only 1974 letter processed for DNA according to the chart). This sounds plausible, because recent information has shown that the Exorcist letter is without doubt genuine Zodiac correspondence based on comparisons between envelopes. All of this should exonerate David Toschi of having any involvement in forging Zodiac letters, and exclude Arthur Leigh Allen once and for all. But if the Exorcist letter and 1978 letter matched in DNA - and the 1978 letter was considered a forgery by investigators - why hasn't the Exorcist letter been more heavily questioned as authentic? Irrespective of any matches noted by Alan Keel, if the 1978 letter provided a DNA sample, then we may be able to identify the Zodiac Killer if the arguments made using the Melvin Belli letter stack up.
ADDITIONAL READING: A PATTERN OF WRITING