This should be proof enough that the "concerned citizen" had read the Chronicle article, knew the code had been broken, and knew Donald Harden's worksheets had already been sent to the Vallejo Police Department and Sergeant John Lynch. Therefore, do you have to question the integrity of the "concerned citizen" regarding the motivation behind his August 10th 1969 mailing?
So, having presumably read all this, was the "concerned citizen" just a helpful member of the public attempting to corroborate the Harden's solution, or did the Zodiac Killer, knowing his cipher had been broken quickly, begin playing a game of 'cat and mouse'. The author of the "concerned citizen" card didn't want to give the Vallejo Police Department his name for fear it would be published in the newspapers, just like Zodiac stated in the 408 - but did the anonymous card reveal his identity?
The "concerned citizen" card only contained 69 words, so why did the sender bother to type the message rather than write a handwritten message or simply capitalize the text.
When he wrote the cipher key he capitalized the alphabetical letters to mirror the 408, so what purpose was behind him choosing not to do this in his message?
The sender would certainly not have given away his identity by using upper case lettering in the message (as he had already done it in the key), nevertheless, he chose to type it anyway. If the author was the Zodiac Killer, did he believe, that by using capitals in his message rather than handwriting it may have been construed as suspicious, so opted to use a typewriter for a more professional approach and give the card a level of credibility. Opting to write the message in his normal handwriting would obviously have given the game away. He also may have thought it easier to type the message rather than make the effort to disguise his handwriting. The cipher key was obviously written rather than typed because of the unusual characters present within the 408 cipher not being available on a standard typewriter.
This may have been the Zodiac Killer's idea of a joke, after having previously stated "I want you to print this cipher on the front page of your paper. In this cipher is my idenity."
This contradiction certainly wouldn't have been lost on a killer who craved attention at every turn.
A killer who was prepared to confuse with "name" and "identity" in his first communications with the newspapers, would not be averse to creating similar parallels with "signature" or "name" in the "concerned citizen" card just ten days later.
THE CONCERNED CITIZEN CARD [PT1] THE CONCERNED CITIZEN CARD [PT3]