What, if anything, lies within the 'Confession' letter to suggest this declaration of murder was in any way related to the other crimes that began on December 20th 1968, just over two years later. It has been previously pointed out, that the author of the 'Confession' letter used the wording "She squirmed and shook as I choaked her. And her lips twiched". This having striking similarities to the 'Little List' letter mailed by the Zodiac Killer mailed on July 26th 1970, in which he stated "Some I shall tie over ant hills and watch them scream + twich and squirm." But more apparent, is the egocentric nature displayed in the 'Confession' letter, that he maintains throughout his correspondence to the authorities, right through to the Exorcist Letter mailed on January 29th 1974, revealing character patterns of his own unique writing style. In the 'Confession' letter his extreme use of the word 'I' appears no less than 19 times, along with his use of 'me', 'my' or 'mine' a further 12 times in this short letter comprising of 423 words. So, in total, a reference to himself appears no less than 31 times. That is 7.33% of the time, or once every 14 words - and something we were going to get accustomed to over the following eight years.
The 'Bus Bomb' letter, 'Little List' letter and 'Melvin Belli' letter are further examples of the Zodiac Killer's compunction to constantly refer to himself as the focus of attention within his writings. In the Melvin Belli Letter this occurs 16 times within the body of text, containing 134 words (11.94% of the letter). The 'Little List' letter contains 12 in 178 words (10.07% of the letter) and the 'Bus Bomb' letter is equally high in frequency.
When the 408 cipher was solved in a matter of days by Donald Gene and Bettye June Harden, the author revealed his 'Most Dangerous Game', believed to have been inspired from a book authored by Richard Connell and published on January 19th 1924. The short story describes a hunter, who disillusioned with tracking down animals, turns to the more thrilling experience of hunting humans instead.
This early 'Confession' letter may have been the precursor to the 408 cipher and the early thought processes of a man soon to become the Zodiac Killer, when he typed "I am not insane. but that will not stop the game" and "I am stalking your girls now".
In the 'Dripping Pen' card and 340 cipher the Zodiac Killer appeared to hand us a chronological timeline of his murders. He refers to December, July, August, September and October = 7. If indeed it was chronological, then five murders would be accounted for, leaving two murders in August unexplained.