Some websites have explored the possibility that a silencer was used in the Blue Rock Springs Park attack on Michael Mageau and Darlene Ferrin on July 4th 1969, while others argue the contrary, resulting in much debate on many Zodiac Killer forums. Nobody knows for sure, however, here we will be experimenting with the idea that indeed a silencer was used in the commission of the Blue Rock Springs attack, with an argument presented that a silencer or modified compressor was either used or carried during all four attacks attributed to the Zodiac Killer over his deadly ten-month reign. We will begin the analysis at the location of his second crime in the parking lot at Blue Rock Springs just after midnight, as the July 4th 1969 celebrations were slowly ebbing away.

July 4th (or Independence Day) is a federal holiday commemorating the independence secured from Great Britain on July 4th 1776, which is celebrated annually with fireworks, parades, family events and such like. But for one person the festival of goodwill was clearly of no concern, as he raised his 9mm Luger to the open passenger side window of Darlene Ferrin's brown Corvair - and without uttering a word - unleashed a volley of gunshots into both victims. The perpetrator then retreated back to his vehicle, only to realize that at least one of his victims may still be alive, so returned and fired off a further four rounds at the defenseless young couple. In just under forty minutes the relatively quiet neighboring towns of Vallejo and Benicia were about to receive a rude awakening, as the Zodiac Killer made contact for the first time in a payphone call that police dispatcher Nancy Slover was never to forget. 

In the police report by the Vallejo Police Department, Michael Mageau stated that as the assailant approached his passenger side door he reached for his wallet, believing the person to be a policeman. He was in the process of doing this when he heard a muffled sound and felt a pain in his back and neck area. He then heard further muffled sounds, that he interpreted as a gun with a silencer on, before the killer returned a second time and fired a couple more shots into Mageau as he attempted to cower on the back seat of the Corvair. Michael Mageau clearly states that all the shots he heard that night were muffled - again sounding as if a silencer had been employed. He did not state that the first shot was really loud and the remaining shots were muffled. If a silencer had not been employed, then clearly the first deafening shot at such close range would have understandably impaired his hearing to any subsequent shots fired off by the perpetrator that night. Michael Mageau appeared to imply that all the shots were muffled. This interview was conducted at the intensive care unit of the Kaiser Hospital on July 6th 1969, being one of Michael Mageau's earliest recollections.   

This was a life changing event for Michael Mageau, as was the phone call to police dispatcher Nancy Slover. She claimed right up to her death that the voice she heard over the phone that night is something she was never likely to forget. Some of Michael Mageau's memories of the night have altered over intervening years, but it is proposed here, that if he said two days after the attack that all the shots were muffled, then this would be the most reliable testimony he was ever likely to give. As your ear enters into trauma after the first shot, it must make the subsequent shots audibly different from the original. This, however, is a distinction Michael Mageau never made, simply stating "all the shots were muffled".

George Bryant resided in a caretakers house near the Blue Rock Springs parking lot, from where he heard the events unfold that night from approximately 800 feet away, describing the following sequence of noises. He stated that he heard "one gunshot", then a moment later "another gunshot", then after a further gap the sound of "rapid gunfire". This sequence of events markedly differed with the chain of events described by Michael Mageau, He recalled how "a white man drove up in a car, got out and walked up to their car, shined a flashlight inside and started shooting". The man then left for a brief time, before returning and firing off four more rounds. It is without doubt that Michael Mageau was under unfathomable stress that night and may have been understandably confused about the exact sequence of events that transpired, whereas, from the relative calm of his occupancy 800 feet away, George Bryant was able to give a much more reasoned and accurate account of events. He was also able to discern the difference between firecrackers being let off that night and the sound of gunfire, which he assuredly claimed were much louder. But could he?

In Corpus Christi, the two holiday dates of January 1st 2012 and July 4th 2012 were analyzed, when fireworks were most prevalent. Of the 625 emergency 911 calls received that year concerning gunshots fired, 379 were reported on these two dates alone, suggesting a significant proportion of the general public mistook fireworks for gunshots. The following video demonstrates the sound of firecrackers and gunshots, indicating that over as little as 30 yards the sounds become more indistinguishable. The greater the distance, the harder they are to tell apart. George Bryant was 800 feet from the parking lot of Blue Rock Springs. They become even harder to tell apart from within the confines of a building.
https://www.youtube.com/watch?v=oYqPAkCZfiI

We also do not know where all the sounds heard by George Bryant that night came from. Were they from Blue Rock Springs parking lot, Columbus Parkway, directly above his house or elsewhere? Without being able to determine the distance of each sound, it is impossible to determine their volume at source. So, the fact he heard some sounds louder than others is no proof of gunshots - only a perceived notion of gunshots from his standpoint.

The Zodiac Killer claimed to use a pencil flashlight to aid his aim during the Lake Herman Road double murder of David Faraday and Betty Lou Jensen on December 20th 1968, so appeared adept at modifying his weapon to suit his purpose. He also gave us a detailed description of his bomb making plans in the Bus Bomb letter on November 9th 1969 and April 20th 1970 communication, so it is actually no great leap of faith to believe that he was able to create a fully functioning homemade suppressor attachment for his gun also - or possibly own the real thing.

David Faraday and Betty Lou Jensen were mercilessly gunned down in a lonely turnout on Lake Herman Road in Benicia on December 20th 1969. David Faraday was shot once behind the left ear and Betty Lou Jensen was struck five times in her back as she fled for her life across the gravel turnout, obviously in a desperate bid for freedom. However, she managed just 33 feet from the rear of the Rambler, before collapsing backwards onto the turnout floor. At least ten shots had been fired that fateful night, testinony to which lay the strewn cartridge casings on the gravel turnout. 

Lake Herman Road traveled through undulating hills and trees as it meandered from Benicia to Vallejo in near total darkness. On the night in question it was also extremely cold, just 22 degrees Fahrenheit with the ground frozen under foot.

The sound of gunfire can travel for several miles, depending on the type of weapon, air temperature, humidity, the surrounding terrain, etc. The sound of a bullet being ejected will travel further in cold air, which has a greater density than warm air, however, Lake Herman Road was (as Zodiac stated), surrounded by high hills and trees which would help to contain any localized noise. Regardless of this, we have to consider it was about 11:15 pm at night, with local residences scattered along Lake Herman Road. Why would the Zodiac Killer attract unwanted attention to himself when his exit strategies are limited? There is one main exit road to the west and limited choices to the east. To travel eastbound and exit Lake Herman Road would take approximately 2-3 minutes, whereas westbound would take marginally longer, at around 4 minutes. Any respondents to the sound of the gunfire could conceivably have passed him as he fled the scene of crime. An unnecessary risk and one he needed never take.

James Owen, who passed by the scene just before the murders, mentioned no gunshots in his first statement to police on December 21st 1968, however,  three days later he stated "that he thought he heard a shot" approximately a quarter of a mile after he passed the turnout. On a quiet country road at approximately 11:15 pm at night, are we to believe the killer only waited 30 seconds after James Owen had passed before firing off numerous rounds from a .22 caliber weapon? But Owen supposedly only heard one. After James Owen passed the turnout, are we to conclude the Zodiac Killer only shot David Faraday (the shot James Owen heard), then waited a certain length of time until James Owen was out of earshot, then murdered Betty Lou Jensen? The sequence of events makes little sense from either perspective - and in all probability James Owen heard nothing. 

Then we had the murder of Paul Stine in the wealthy district of Presidio Heights on October 11th 1969. His dormant taxicab lay motionless at the corner of Washington and Cherry Streets, yet to be known that the Zodiac Killer had brought his reign of terror to the midst of San Francisco. The Zodiac Killer was witnessed by three teenagers across the street exiting the taxicab, before heading away from the crime scene north up Cherry Street. They stated they heard no gunshot. 

The Zodiac Killer would claim the murder of Paul Stine just two days later in a letter mailed to the San Francisco Chronicle, stating "I am the murderer of the taxi driver over by Washington St + Maple St last night". The three teenage  eyewitnesses (or anybody else) failed to hear any gunshots at the intersection of Washington & Cherry, as was the case at Washington & Maple. At 9:55 pm at night, why was this?

This crime had all the hallmarks of pre-planning, with the Zodiac Killer even removing a section of Paul Stine's shirt, which he mailed two days later along with the letter. But despite being a far more populated area, in which he secured a trophy from the crime scene, it was an unnecessary risk he was prepared to take. Again, imagine you were the perpetrator. Would you fire a loaded, unsilenced weapon within feet of a house, then proceed to start rummaging through the victims pockets, wipe down the inside of the cab, exit the vehicle and proceed to the exterior doors and start wiping them down, before moving off casually - or get the hell out of there? If the Zodiac Killer had used a silencer and believed no witnesses had observed him and called the police, then quite possibly he may have showed less urgency.  Which is exactly what the Zodiac Killer did. Finally, we will move to the brutal stabbings at Lake Berryessa, resulting in the murder of Cecelia Shepard on September 27th 1969.

Again, access to and from the scene of the crime along the Knoxville Road was limited. It was not a short journey back to the main arterial roads and on to Main Street in Napa, so the last thing the Zodiac Killer wanted to do was blast away with his weapon on the shores of Lake Berryessa, thereby creating the feeling of entrapment, with limited exit strategies. This is probably why the Zodiac Killer switched  from gun to a knife in the close quarter attack on Bryan Hartnell and Cecelia Shepard.

Bryan Hartnell observed the Zodiac Killer's gun up close and there was no suggestion of a silencer. But this does not necessarily mean he was not carrying one. However, on this occasion his knife would seve as the perfect silencer. The Zodiac Killer first presented his gun to the young couple - and although the ordeal was undoubtedly terrifying - there may have been little reason to suspect anything other than robbery as a motive at this point. The time was approximately 6:15 pm in the evening and it was still light. There were other people in the vicinity (although not many), and the thought that the assailant would start firing away with restricted exit points seemed unlikely. Unbeknownst to the couple, the assailant possessed a silent weapon, which had they seen from the outset, greater danger may have been inferred. The knife, from the perspective of the Zodiac Killer, was the perfect choice. 
The Zodiac Killer may not have used a silencer in any of the crimes, but there is one question you have to ask yourself. If you were the Zodiac Killer, hell bent on creating a legacy of evil and considering the locations he chose, would you have used a silencer?

Paul Stine arrived for work on October 11th 1969 at 8.45 pm, having taken one fare from Pier 64 to the Air Terminal, before the ill fated decision to pick up his murderer close to the corner of Mason and Geary Street in the theater district of San Francisco. In a little over ten minutes he lay dead from a single gunshot to the anterior of his right ear, discovered slumped across the passenger side of the front seating. Three young witnesses across the street from a nearby residence recalled seeing a man in the front of the taxicab, the victim slumped over his lap, wiping down various sections of the interior and leaning over towards the driver side compartment. He then exited the taxicab and proceeded to the driver side door, that faced into the street, which he then wiped down, presumably to remove fingerprints. However, if this were the order of events, how did the murderer ever place himself into contact with the driver side door or panel of Paul Stine's taxicab.  The only reason to have touched the driver side door of the taxicab or its adjoining panel, was that he either leaned on it after he summoned the taxicab at the Mason and Geary intersection and spoke to Paul Stine, or he actually opened the driver side door to gain access to the vehicle. The first option seems unlikely, knowing that in a matter of minutes he is about to put a gun to the head of the taxicab driver and brutally execute him, so leaving fingerprints in advance on a door, he later has to waste time removing after the murder seems unnecessary.    

But lets go back to basics and examine the evidence as we actually know it, beginning with the Zodiac Killer letter mailed to the San Francisco Chronicle on October 13th 1969, in which he states ''I am the murderer of the taxi driver over by Washington St + Maple St last night'. Why does the killer mention Washington and Maple when the taxicab was found at Washington and Cherry. He clearly had knowledge of his location as he refers to both street names, and although the Zodiac Killer could not be taken at face value, there was nothing to be gained by claiming the murder at the wrong location, and for this reason alone we have to conclude that this is probably where Paul Stine was shot. There are three key pieces of reasoning that point us towards this hypothesis, namely that the three teenage eyewitnesses from the house overlooking the intersection of Washington and Cherry Street did not recall hearing any gunshot at this location, albeit, this may have resulted from the possibility that a suppressor was employed in the commission of the crime, or from the close contact wound that muffled the sound. Secondly, the blood pattern on the Paul Stine's shirt that tells its own story. 

And finally the killer was seen wiping down the driver side door, one assumes to remove any incriminating fingerprints. These three key ingredients may tell us the true story of the events that unfolded on that fateful night back on October 11th 1969, and one that differs substantially from the widely believed order of events.
As the taxicab approached the corner of Washington and Maple Street, Paul Stine did not place the car into park, knowing he was on a 'run through' to his original fare at 500 9th Avenue, radioed to him by Yellow Cab dispatcher Leroy Sweet, when suddenly the killer raised the gun into Paul Stine's eye-line. It clearly states on the autopsy report there were dark marks on the dorsal side of the Paul Stine's left hand, that may suggest that as Paul Stine reacted to move away from the danger, his left hand was raised in order to deflect the gun away at the instant of firing, resulting in dark stippling marks. During this melee, Paul Stine inadvertently broke contact with the brake pedal, causing the taxicab to motion forward out of control, possibly towards the sidewalk. Wanting to avoid an imminent crash and alerting the entire neighborhood, the Zodiac Killer either lunges forward to grasp the steering wheel and clambers over to the front of the taxicab to regain control of the vehicle, or exits the left rear passenger door and enters the driver side door. He then has to push his body weight against Paul Stine (who remains in a sitting position), against the driver side door to access the vehicle controls and thereby coast the taxicab to the corner of Washington and Cherry Street where he finally parks up.

The blood pattern on Paul Stine's shirt indicates that for a measurable time period his body must have been in an upright position, to display the pattern exhibited by the photograph on the left. If Paul Stine had been shot at Washington and Cherry Street and had immediately slumped over to rest on the front passenger side seat, shown in the crime scene photographs, the blood pattern would be altogether different. The shirt displays blood from a head wound, falling with gravity, downwards and around the chest, predominating on the right side, as he was shot behind the right ear. The idea Paul Stine was pushed against the left driver side door when the Zodiac Killer commandeered the vehicle, is also exhibited, as the angle of body tilt would lead to blood flow on this side also, albeit marginally less in the pattern displayed. This concept was further analyzed in a previous    

article, suggesting that the Zodiac Killer for this reason walked on the north side of Jackson Street, so that his predominantly blooded left side faced away from the roadside and any oncoming traffic and police vehicles. If his left side had not been covered in blood, walking on this side of the street, in closer proximity to oncoming headlights would have seemed the less preferred option.  See http://www.zodiacciphers.com/zodiac-news/the-silent-murder-at-presidio-heights.
However, we have a problem;  If the Zodiac Killer had jumped from the back seats to the front and gained control of the taxicab by leaning against Paul Stine, at the end of the journey, it would not have necessitated the murderer walking from the front right passenger side door to wipe down the exterior of the driver side door and panel. The fact he did indeed perform this action suggests at the very least he must have deposited fingerprints on it at an earlier time. As explained earlier, if he had hailed the taxicab by approaching the driver side door at Mason and Geary Streets with murder on his mind, the last thing he would have done was to touch the driver side door handle, an action that necessitates the later removal of fingerprints. If the Zodiac Killer had remained in the rear of the taxicab for the entire journey, why on earth after killing Paul Stine, would he be wiping down the interior driver side compartment of the taxicab, after all, there was no reason to have ever touched these areas. If he had opened the right front passenger side door with the express intention of removing a piece of Paul Stine's shirt, the only three things he needed to touch would have been the rear right door handles, the front exterior passenger door handle and Paul Stine's shirt, nothing else. The wiping down of the interior of the cab and exterior driver side door makes little sense, unless he touched it.

This suggests the Zodiac Killer must have touched the driver side door handle other than at Mason and Geary Streets and Washington and Cherry Streets. The only remaining option being the Washington and Maple Street intersection, where he claimed to have committed the murder all along. However, this would debunk the idea, the killer clambered from the back seats to the front seats. The only possible scenario left that makes any sense, is that when the vehicle ran out of control, he quickly exited the vehicle on the roadside, opened the driver side door of the taxicab with his left hand, deposited blooded right fingerprints on the door panel as he braced himself against the moving vehicle, and stepped over the lifeless body of Paul Stine touching the driver side compartment as he did so. 

The most credible course of events, is that after shooting Paul Stine the vehicle motions forward. The Zodiac Killer reacts instantly by exiting the left rear door, opens the driver side door, grabs the steering wheel, then steps over the motionless Paul Stine, closes the door and uses his left foot to access the taxicab pedals and coasts the vehicle one block further on, where he ultimately disappears north along Cherry Street. This covers all of the known facts, the blood pattern on the shirt, the necessity to wipe down the driver side door handle, the necessity to wipe down the interior driver side of the cab and his decision to walk on the north side of Jackson Street, in the full glare of police headlights heading towards the crime scene at the Washington and Cherry Street intersection 
Donald Fouke, a police officer responding that night, recalled a man walking with a shuffling lope along the north sidewalk of Jackson Street, heading towards the intersection of Jackson and Maple. If, as hypothesized, the Zodiac Killer exited the moving taxicab at Washington and Maple, is it possible he injured his ankle or leg in the process, resulting in the 'shuffling lope' described by Donald Fouke from his patrol car. The direction of the Zodiac Killer also makes sense, in that, if he had killed Paul Stine at Washington and Maple without any mishaps, he would likely have been walking north along Maple Street towards the Jackson and Maple intersection, the direction he was ultimately heading when spotted by Donald Fouke, only he had traveled one extra block unnecessarily. 
​
http://www.zodiackillerfacts.com/blog/mysteryquest-paul-holes-and-the-murder-of-paul-stine

Edward Edwards was a convicted serial killer who spent time at Old Montana State Prison and recollects in his autobiography 'Metamorphosis of a Criminal' memories from his time there, on this particular occasion another inmate, stating 'this man remains my most uncomfortable memory'. He goes on to say 'This demented individual showed an overwhelming interest in science fiction and Egyptian literature.' He also recollects that this individual believed that anyone he killed would become his slave in the next life. Whether or not this man was the Zodiac Killer is open to debate, but what we do know is that the Northern California killer appeared on the face of it to be immersed in history, often indicating in his literary correspondence and the symbolism contained within it, the ability to reference material that predated his existence, none more so than the Little List Letter, mailed to the San Francisco Chronicle on July 26th 1970. This lengthy correspondence paraphrased the Gilbert and Sullivan opera The Mikado, not once, but twice and backed this up with further reference in his Exorcist Letter, four years later when he pulled lines from Mikado Act 2, On a Tree by a River.
Using these above premises and the fact the Zodiac Killer tabled us his Little List on July 26th, it begged the question, did the murderer of innumerable people in the late 1960's and early 1970's, do so randomly when the compulsion desired or did he indeed stick rigidly to a plan, when he selected his victims, to be placed on his so called 'Little List'.
The next section is an expansion to the article 'The 13 Moon Calendar Crimes', exploring the idea that the Zodiac Killer did indeed have an agenda and one he remained loyal to, throughout his seemingly motiveless crimes. It became apparent that the Zodiac Killer selected his murders on nothing else but time, or to be more specific, by the date on a calendar. 
The Little List Letter was indicative of a killer, tired of the public, not seeing the whole picture, so within this correspondence he would give us at least four clues   

Firstly the reference to the Mikado, a two part comic opera by Gilbert and Sullivan, which opened for the public on March 14th 1885, and was hugely successful running for 672 performances at the Savoy Theatre in London. The key was in the date.
Secondly, was the reference to the number 13, and as one can see the thirteenth line of his recital implored us to see that his Little List 'are up in dates'.
Thirdly, was the date he mailed us his Little List Letter, July 26th, the most significant of all his clues.
Fourthly, 'As some day it must happen', along with a back reference from the 13 Hole Postcard 'The pace isn't any slower, in fact it's just one big thirteenth'.
All these clues are suggestive of a date specific element and would be found within the 13 Moon Calendar.
The 13 Moon Calendar was embedded in many ancient cultures, the star Sirius being integral to their beliefs. The heliacal rising of Sirius on July 26th, initiated the beginning of the Egyptian year and brought about the 1460 year Sothic cycle. The 13 Moon Calendar, consisting of a 13 month, 28 day cycle, was used by the Egyptian Thoth, Druids, Polynesians, Incas, along with some native Americans. The 13 Moon Calendar reflects this movement of Sirius and itself begins on July 26th, as opposed to our traditional Gregorian Calendar that begins the year on January 1st. Each month of 28 days is split into 4 weeks of 7 days and as such there are only four days per month that comprise a weeks beginning. That is day 1, 8, 15 and 22, shown here below left.
To view the 13 Moon Calendar and check the relevant dates in this article, open this page from the Law of Time website and scroll down the page to the large chart that begins with the Magnetic Moon. For example December 20th in the American system is written as 12/20. Keep this tab open.  http://www.lawoftime.org/thirteenmoon/tutorial.html

You will note that position 1, 8, 15 and 22 are all the first day of a calendar week.
Each month there are 28 days, so if the Zodiac Killer was selecting his victims randomly there would be an 85.7% chance they would not fall on the first day of the 13 Moon Calendar week, conversely if the Zodiac Killer was selecting his victims randomly there would only be a 4 in 28 chance or 14.3% chance they would be murdered on either day 1, 8, 15 or 22.
Of course it may be possible that one victim may fall on this date, but what are the odds for two, three or indeed thirteen. If they were murdered randomly then you would expect a random spread, but if the majority or all fell on the first day of the 13 Moon Calendar week, then that 14.3% chance becomes smaller and smaller with each victim, until the odds become that slim, you have to start believing that a correlation exists. The only other possibility is that miracles are a believable concept, however, it is not only the murders themselves we should consider, it is the Little List Letter itself.
The mailing of this letter was July 26th, which falls on the first day of the 13 Moon Calendar week and notably it is the beginning date of the 13 Moon Calendar also. The letter featured the Mikado which opened to the paying public on March 14th 1885 and March 14th also falls on the first day of the 13 Moon Calendar week. One letter, one list and two dates that fit into our criteria straight away, so lets move on. 
Two early crimes often linked to the Zodiac Killer were the murders of Robert Domingos and Linda Edwards on a remote Santa Barbara County beach on June 4th 1963 and the brutal stabbing of Cheri Jo Bates outside the Riverside City College Library on October 30th 1966, however neither of the crimes were specifically claimed by the Zodiac Killer, only a belated reference was made in the Los Angeles Letter mailed on March 13th 1971, when he stated 'I do have to give them credit for stumbling across my riverside activity', furthermore both of these crimes were committed in the pre-Zodiac era and neither date falls on the first day of the 13 Moon Calendar week, suggesting they were not the work of the Zodiac Killer, or were not committed under the Zodiac umbrella, however on December 20th 1968 things were about to change.   

The Lake Herman Road murders were the first confirmed attacks by the infamous Zodiac Killer, which he laid claim to on July 31st 1969, in three letters he mailed to authorities, that left us in no doubt we had a serial killer on our hands, indeed, claiming not only the murders of David Faraday and Betty Lou Jensen on December 20th 1968, but the murder and attempted murder of Darlene Ferrin and Michael Mageau at Blue Rock Springs Park in Vallejo on July 4th 1969. Even placing a phone call shortly after the second attack to police dispatcher Nancy Slover, to confirm the horror of that night's events and what would soon follow.
Both of these attacks and the three murders would now begin the infamous Little List the Zodiac Killer was compiling, as December 20th and July 4th would both fall on the first day of the 13 Moon Calendar week. Slim odds indeed, but this unfortunately was just the beginning. 
Almost three months later initial fears were well founded, when a masked assailant approached a courting couple on the shores of Lake Berryessa and after hogtying both Bryan Hartnell and Cecelia Shepard began his savage attack, stabbing the couple numerous times. Sadly Cecelia Shepard succumbed to her injuries two days later, but miraculously Bryan Hartnell survived and was able to recount the horror of that day from his hospital bedside. 
Even more miraculous was the date of the attack, September 27th 1969, another date that would just happen to fall on the first day of the 13 Moon Calendar week and our odds are getting slimmer. Curiously, even though all three attack dates fell on the first day of the week, they also all fell on position 8, possibly giving rise to the 888 on the 13 Symbol Cipher, but this is speculative at best.
Exactly two weeks later the Zodiac Killer changed course, when he took his murderous campaign across the bay to San Francisco, resulting in the callous assassination of taxi driver Paul Stine, discovered prostrate across the seat of his resting vehicle. The Zodiac Killer came into brief view for but a moment, witnessed by three teenagers from a house window across the street, but unfortunately he would make good his escape, exiting north along Cherry Street, an affluent neighborhood of Presidio Heights.

After this murder, the Zodiac Killer was never witnessed again, but by all accounts left his bloodied fingerprints, as testimony to a man that has subsequently become the most infamous killer in US history. But one further fingerprint was to be laid down, the date of his supposed final murder, October 11th 1969 and one more date that would fall on the first day of the 13 Moon Calendar week, indeed October 11th 1969 was a new moon, so from the perspective of the night sky, it could not have been darker, lending irony to a calendar date, that would yet again provide a significant ally to shield this killer as he dissolved into the shadows for one last time.
We now had four dates and four correlations, the odds are shortening, but don't believe for a minute that the coincidences stop there.
On November 8th 1969 his most infamous correspondence would land at the doorstep of the San Francisco Chronicle, another hidden clue would be contained within its envelope, in the form of a cipher, one that has remained unsolved to this day. However the number 888 may again have resurfaced within the code, to be found embedded within the name of Zodiac itself.
This concept is explored linking six or more correspondences of the Zodiac Killer together, including all his unsolved ciphers and can be viewed in the article 'The Three Unsolved Ciphers Linked'.
Not surprisingly, the date of November 8th fits our criteria and falls on the first day of the 13 Moon Calendar week.
The next correspondence to arrive was the Melvin Belli Letter on December 20th 1969, the anniversary of the Lake Herman Road double murder and that significant date once more. The letter itself states 'I am afraid I will loose control again and take my nineth + posibly tenth victom'. Considering the Zodiac Killer's history of attacking mainly couples, there was a distinct possibility his ninth and tenth victims may be a courting couple once more. So bearing in mind our 13 Moon Calendar, the next murders would likely fall on the first day of the calendar once again and the murders would show traits of the Zodiac Killer. We wouldn't have long to wait.
Two months later on February 21st 1970 John Franklin Hood (24), who had served decorated time in Vietnam in the 64th Armored Division and Sandra Garcia (20), who worked in the California Department of Motor Vehicles, decided to visit the quiet retreat of East Beach, Santa Barbara one evening, when they fell victim to a knife wielding assassin, not unlike the Lake Berryessa Attack on Bryan Hartnell and Cecelia Shepard and more crucially, unlike the murders of Robert Domingos and Linda Edwards, within the Zodiac timeline. February 21st falls on the first day of the 13 Moon Calendar week for the fifth attack in a row and all within the framework laid down within the Melvin Belli correspondence. The next letter to arrive on April 20th 1970 was the 13 Symbol Cipher and our worst fears would be realized, the Zodiac murder total had reached ten, indicating that two more victims had been placed on his list, the question being, were they John Franklin Hood and Sandra Garcia.
It can also be noted that on the 'My Name is....Cipher' letter, the Zodiac Killer wrote 'I have killed ten people to date', it is a matter of interpretation, he may possibly have killed ten people up to this point in time, but if these were his victims, he most certainly had killed 'ten people to date'. 

Next up was the abduction of Kathleen Johns, an account of which has always been heavily questioned. The date of the Modesto abduction was March 22nd 1970, superfluous in this case, as Kathleen Johns was not murdered. The Zodiac Killer had never showed any hesitation or leniency in any of his previous attacks, but if we are to believe this was our murderer, he appeared wholly indecisive, driving Kathleen Johns around for approximately two hours, whereas during his previous remote attacks, he presented his weapon and death was soon to follow. If we use his modus operandi as a guide and the date of March 22nd, which fails to fall on the first day of the 13 Moon Calendar, the two are compatible and lend weight to the hypothesis, that this crime was not the work of the Zodiac Killer. 
Along came another anniversary, that of July 4th 1970, exactly one year after the attack at Blue Rock Springs Park, but this night would again be no stranger to horror, when on another beach, this time in Santa Barbara, three men Thomas Victor Dolan (17), of Manhattan Beach, Thomas Hayes (19), of Hermosa Beach and Homer Clyde Shadwick (19), of Saginaw Michigan were brutally attacked with bladed instruments while they lay defenseless in their sleeping bags. Two of the victims succumbed to their injuries, while the third Thomas Hayes was rushed to hospital in nearby Goleta, in critical condition, but fortunately survived. Another anniversary, another relevant date, but sadly two more murders.
The Zodiac Killer may now have claimed nine victims in six different attacks, David Faraday December 20th 1968, Betty Lou Jensen December 20th 1968, Darlene Ferrin July 4th 1969, Cecelia Shepard September 27th 1969, Paul Stine October 11th 1969, John Hood February 21st 1970, Sandra Garcia February 21st 1970, Thomas Dolan July 4th 1970, Homer Shadwick July 4th 1970, all of which fall on the first day of the 13 Moon Calendar week.
A further two months later Donna Ann Lass disappeared, feared murdered after leaving the Sahara Tahoe Hotel, where she was employed as a nurse. Her case became entwined within the Zodiac sphere after the arrival of the Pines Card communication, suggesting a link to the Donna Lass case, however this was not the only reason, as her disappearance came just six months after the abduction and murder of another nurse Judith Hakari. She had been working at the Sutter Hospital in Sacramento on March 7th 1970 and later had pulled into the parking lot of the Markston Apartments, where she was likely abducted. One and a half months later she was discovered in a shallow grave, she had been beaten and strangled, but not sexually assaulted. Both the abduction and possible murder of both Hakari and Lass occurred on the first day of the week on the 13 Moon Calendar.         

Shortly after the disappearance of Donna Lass and two days prior to the Halloween Card, on October 25th 1970 Nancy Bennallack, a court reporter was found murdered, brutally stabbed numerous times in her own apartment. This, if indeed it was the Zodiac Killer would suggest a marked deviation from his previous crimes, however she was described as strikingly similar in appearance to Judith Hakari and was murdered just one block away.
October 25th falls yet again on the first day of the 13 Moon Calendar week. The Bermuda Triangle website describes these three murders as the Nightingale Murders, so for a more detailed connection and background to these cases, please visit bermuda-triangle.org/.
By the time the Halloween Card arrived the above murders would total 12 and the Halloween Card was suggesting that Paul Avery, a reporter at the San Francisco Chronicle may possibly become the Zodiac Killer's fourteenth victim. 
There is no suggestion that all these murders are the work of the Zodiac Killer, however they are the most commonly linked ones and most are credible possibilities, occurring within a relatively short time frame of 22 months. In other words 12 murders in 22 months, and all falling on the first day of the week on the 13 Moon Calendar. Three further victims, firstly, that of Robin Graham (18) who disappeared in the early hours of November 15th 1970 on the Hollywood Freeway after encountering car problems and noticed in the company of an unidentified dark haired male in possession of a pale Chevrolet Corvette. Secondly Jeanette Kamahele (20) on April 25th 1972 last spotted on Highway 101 Santa Rosa being aided by a white male driving a light brown Chevrolet pick up truck. And finally the strangled body of Lynn Maureen Derrick (24) found on a Sausalito side street on July 26th 1972, believed to have been murdered elsewhere and dumped, with the sound of a speeding car leaving the scene. These final three murders also fit the 13 Moon Calendar criteria and could push the final Zodiac total to 15, based upon date specifics. If Lynn Maureen Derrick was the Zodiac Killer's final victim it would be have not gone unnoticed that she was murdered on July 26th, the date the Little List was mailed to the San Francisco Chronicle and the beginning of the 13 Moon Calendar year, to mark, quite possibly the start of the end.    
What makes it even more striking, is that if you visit either the Zodiackiller.com forum or the Zodiackillersite forum, and select possible victims before the Lake Herman Road murders on December 20th 1968 and after the murder of Lynn Derrick on July 26th 1972, you will be hard pushed to find any murders that fall on the first day of the 13 Moon Calendar week, showing it is indeed a rare occurrence, but during this brief 22 months it occurs 12 times. If we include the disappearance of Robin Graham on November 15th 1970, this elevates to 13 in 23 months and would have come within one month of the Halloween Card seeking a fourteenth victim.
Coincidences rarely equate to facts, as many Zodiac suspects can testify to, but sometimes you just wonder.   

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