There is a case to be made that the Zodiac Killer placed five X's around his crosshairs on the Bus Bomb letter that aligned his attacks to the numbers on a clock face, tilted clockwise using magnetic north. This may have been the rudimentary precursor to his use of radians on June 26th 1970 and July 26th 1970 using Mount Diablo as the origin point. All of the canonical Zodiac attacks could have been deliberately chosen because of their location to satisfy this template, but only the murder of Paul Stine in Presidio Heights on October 11th 1969 was particularly fluid, in that the Zodiac Killer could engineer a precise location by directions issued to the taxicab driver. Paul Stine was murdered alongside 3898 Washington Street in San Francisco, although his original destination according to the trip sheet was the intersection of Washington & Maple streets. This is essentially insignificant when calculating the angle from Mount Diablo, which was 257 degrees in both instances. The 8 o' clock position is situated at 240 degrees, but tilted to magnetic north of 17 degrees in 1969, lands exactly at 257 degrees.
Lake Herman Road and Blue Rock Springs are both encompassed by the 10 o' clock line tilted to magnetic north to make 317 degrees (30 by 10 plus 17). The Lake Herman Road murder site actually sits at 319 degrees and Blue Rock Springs at 318 degrees. Any error must be calculated over 30 degree increments, meaning that the 10 o' clock line (set to Mag. N) is 97% accurate for Blue Rock Springs and 93% accurate for Lake Herman Road. The latter would form the beginning of any predetermined template, because this was the first canonical crime.
While the above three attacks conform largely to the "clock face" theory, Lake Berryessa deviates more significantly by landing at 340 degrees from Mount Diablo (approx 10:54 am/pm). If it conformed to the 11 o' clock position plus magnetic north, the attack should have fell at 347 degrees, so it shows an accuracy of only 77%. The red line below is where the attack should have occurred for 100% accuracy (exaggerated by greater distance). It doesn't fully negate the premise, but it challenges it somewhat. It could suggest that the Zodiac Killer formulated this presentation in the Bus Bomb letter after the fact, because he noticed the rough correlation of his attacks to a clock face. Three other possible explanations could be that the clock face theory is wrong, a daylight attack with a costume and knife created a greater challenge in selecting a suitable location, or the Zodiac Killer originally intended to kill on the eastern side of Lake Berryessa (which is less likely).
The 9 o' clock position, which was the only unidentified line in the Bus Bomb configuration, I believed to be Daniel Williams, who worked at Salesian High School and was targeted by somebody claiming to be the Zodiac Killer in the weeks before the Bus Bomb letter. Salesian High School sat at 283 degrees, whereas the 9 o' clock position plus magnetic north was 287 degrees, an accuracy of 87%. This means we had Lake Herman Road (93%), Blue Rock Springs (97%), Lake Berryessa (77%), Presidio Heights (100%) and Salesian High School (87%). An overall accuracy for the "clock face" theory of 91%..The only attack that allowed him to comfortably take a victim to a specific murder location, rather than being governed by victims needing to be found at a desired location, was Presidio Heights. In this instance, the Zodiac Killer was 100% accurate. Although the Lake Berryessa accuracy was 77%, it only amounted to a 6 mile deviation clockwise from the murder location over 77 miles from Mount Diablo. As a rule (removing the mobile murder of Paul Stine), we would expect the closer the murder site to Mount Diablo, the more accurate the clock face theory conforms in respect to mileage error or fractions of it. Removing Lake Berryessa (and the only knife and daylight crime) from his canonical crimes, we find that the overall accuracy of the clock face theory rises to 97%.
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