"Paul Avery and Kate Coleman who wrote the sizzling expose of Black Panther violence in the July 10th New Times 'have gone out of the area' after receiving the predictable threats", wrote Herb Caen. The bogus letter reopened old wounds, driving the populace to seek closure on the long-unsolved case. Zodiac tips quadrupled. "The Zodiac was shot to death by San Francisco police in March of 1976," a reader informed Caen, "about four months after he set the Gartland Hotel fire that killed thirteen people". Zodiac Unmasked. 
​
On July 19th 1978 a typewritten letter from Los Angeles arrived at the San Francisco Chronicle stating:
"I am the ZODIAC and I am in control of all things. I am going to tell you a secret. I like friction tape. I like to have it around in case I need to truss someone up in a hurry....I have my real name on a small metallic tape. You see, while you have it in your possession, I want you to know it belongs to me and you think I may have left it accidentally. I am athletic. It could be swim fins, or a piece of scuba gear. But maybe you play chess with me. I have several cheap sets in closets all over. I have my name on the bottom of the lid with the scotch tape....My tape is waiting for me all over California. Do you know me? I am the ZODIAC and I am in control". 

Sergeant John Lynch from the Vallejo Police Department interviewed Arthur Leigh Allen, with Allen stating that he traveled to Salt Point Ranch, located on the coast, due west of Napa on September 26th 1969 for a spot of scuba diving. Clearly, Arthur Leigh Allen was a prime suspect for Zodiac, so it must have been obvious to Allen that he would incriminate himself by inserting "swim fins" and "scuba gear" into the narrative of the 1978 letter, unless you believe a double bluff. 

This letter followed the "I am back with you" correspondence mailed to the San Francisco Chronicle on April 24th 1978, just three months earlier. Arthur Leigh Allen had been released from the Atascadero State Hospital on August 31st 1977, and this letter is often touted as his return to the persona of the Zodiac Killer after a lengthy  absence. Or was it more likely that somebody known or unknown to Allen was attempting to implicate him in the murders by dropping subtle clues pointing in his direction? The author of the July 1978 letter seemingly wants to push us in the direction of tape: "I like friction tape", "I have my real name on a small metallic tape", "I have my name on the bottom of the lid with the scotch tape", and "My tape is waiting for me all over California". It appears like a selling job, trying to push the tape angle in connection with trussing people up, whereas the author may have had other intentions.

The Zodiac Killer mailed us a 'Bus Bomb' diagram on November 9th 1969 and April 20th 1970, employing the use of electrical circuits.
'Friction tape is a type of adhesive tape made from cloth impregnated with a rubber-based adhesive, mainly used to insulate splices in electric wires and cables. Because the adhesive is impregnated in the cloth, friction tape is sticky on both sides. The rubber-based adhesive makes it an electrical insulator and provides a degree of protection from liquids and corrosion. In the past, friction tape was widely used by electricians, but PVC electrical tape has replaced it in most applications today. The frictional properties of the tape come from the cloth material, which is usually made from cotton, while the fabric base protects electrical splices against punctures and abrasion. Wikipedia.' 

Was this the implication, with 'pipe bombs' having been discovered at Allen's residence, along with supposed bomb manuals. But more credible, is the emphasis on "swim fins" and "scuba gear," considering Allen's penchant for scuba diving, and the opportunities for such pursuits provided by Lake Berryessa, Lake Tahoe and Fisherman's Wharf near to the Presidio Park - in three Zodiac linked crimes. 
Permanent marker pens, in conjunction with water resistant tape or labels, are ideal for scuba divers and boat enthusiasts for personalizing your equipment. dolphindiveathens.com/marking-your-dive-gear/. "I have my name on the bottom of the lid with the scotch tape....My tape is waiting for me all over California".

With Arthur Leigh Allen the prime Zodiac candidate for many years, isn't it plausible that somebody was attempting to throw Allen under the proverbial 'school bus' in an attempt to keep him in the frame, while keeping an interest in the Zodiac case burning bright. These two letters could actually be from Zodiac (depending on the validity of DNA evidence), and is simply a game by the real killer to keep the spotlight firmly focused on his convenient "fall guy".

There is no hard and fast rule that connects the methodology of serial killers, particularly in regards to the areas they operate and the locations of murder they ultimately choose. But this does not preclude the investigator from forming an opinion on the killer based upon knowledge of the locality, along with geographic profiling, that has suggested a criminal has a comfort zone within which he operates, near to his home or workplace - although a 'buffer zone' will still exist in the mind of the killer, in that he does not wipe his feet too close to home. Can we apply anything we know about the four confirmed attack locations of Lake Herman Road, Blue Rock Springs, Lake Berryessa and Presidio Heights, along with the two Zodiac phone calls placed at the corner of Springs Road and Tuolumne and 1231 Main Street, Napa to this so called 'buffer zone'? It has been suggested that an offender will start their crimes close to home before extending outwards, so as not to draw unwanted attention to themselves, but not too far as to increase the risk of being apprehended on returning back to their comfort zone, to wash or stash away any incriminating evidence they may have unwittingly or deliberately removed from the crime scene.     

When asked whether he thought the Zodiac Killer lived in Vallejo, he responded, "Oh, I think so, he lived in the area, that's for sure, oh yeah, he knew the area".

The second attack, in another secluded area at Blue Rock Springs Park on July 4th 1969, was a four-mile journey northwest of Lake Herman Road, and a 15 minute drive from downtown Vallejo. On this occasion Michael Mageau survived, but unfortunately Darlene Ferrin became the Zodiac Killer's third fatality. This time though, the killer was more brazen, calling police dispatcher Nancy Slover from a phone booth at the gas station at Springs Road and Tuolumne, just a short 10 minute drive from the crime scene. The attack occurred around midnight, with the call logged at 12:40 am. This left 40 minutes of unaccounted time to be explained, leading to the notion the killer returned home first to dispose of any incriminating evidence, including his weapon and possibly clothes, before venturing back out, with renewed confidence, to place the call. This unexplained time could lend greater weight to the theory that the killer was a local to the area of Vallejo, combined with his apparent knowledge of the Lake Herman Road and Blue Rock Springs Park areas.

The third attack at Lake Berryessa, with a driving time of approximately 1 hour and 20 minutes, saw the killer venture further away from the Vallejo area, if indeed he resided there. The male victim, Bryan Hartnell, would again survive, however, the devastating ten knife injuries sustained by Cecelia Shepard would sadly claim her life just two days later at the Queen of the Valley Hospital. The attack took place early evening on September 27th 1969 at around 6:30 pm, with the killer leaving a message at the scene of the crime, on the car door of Bryan Hartnell's vehicle. If we take the message written on Bryan Hartnell's Volkswagen Karmann Ghia door with near accuracy, then the 27 mile journey to the payphone at 1231 Main Street, Napa away from Lake Berryessa, would have taken approximately 50 minutes. The phone call was logged at 7:40 pm, leaving a shortfall of 20 minutes. http://www.zodiacciphers.com/zodiac-news/lake-berryessa-north-of-the-crime-scene-pt2. 
Napa County is a direct route between Vallejo and Lake Berryessa, so if the killer lived in, or very close to Vallejo, he would have left himself approximately 25-30 minutes to arrive home, after placing the phone call. 

The Zodiac Killer's last confirmed murder was that of Paul Stine, on October 11th 1969, leading people to consider the possibility the killer may have been a resident of San Francisco or the Presidio Heights area, bearing in mind his first 14 confirmed letters and cards were postmarked San Francisco, starting with the '408 cipher' mailings and ending with the Halloween Card. But bearing in mind his apparent knowledge of the first two crime scene locations, that a resident of San Francisco would unlikely to be party to, unless a former resident, it is quite plausible he lived somewhere in the region of Vallejo and posted his letters en route to his place of work in San Francisco. The third option being he at one time had lived at both locations. 

The lost 40 minutes after the Blue Rock Springs attack is noteworthy though, in that, did the killer drive home first, remove any evidence, then drive back to the gas station at Springs Road and Tuolumne, or more logically as Mike Morford suggested on Zodiackillersite forum, walk back to the payphone to place the first phone call, thereby attracting less attention to himself?
Quote "I personally think Zodiac lived close to that phonebooth on Springs & Tuolumne, went home, and stashed his gun and car, and walked to the phonebooth. With no car, he was less likely to be noticed". If indeed that was the case and taking into account the time it took him to change, check for any transference from the crime scene, stash the gun and ready himself before venturing back to the payphone, this may have left him with about 15 minutes surplus traveling time, to walk back and make the phone call, putting the Zodiac Killer's residence extremely close to the corner of Springs Road and Tuolumne, or in distance terms, a one mile radius of the payphone.

In the August 4th 1969 'Debut of Zodiac' letter, the author wrote "The man who told police that my car was brown was a negro about 40-45 rather shabbly dressed. I was in this phone booth having some fun with the Vallejo cop when he was walking by. When I hung the phone up the damn thing began to ring & that drew his attention to me + my car". This seemed to suggest he was still using his vehicle at that point, yet it could have been an employed diversion, so as not to expose the close proximity of his home address - with the apparent over emphasis on the wording "me + my car" used to create the same effect, when he quite simply could have said "When I hung the phone up the damn thing began to ring & that drew his attention to me".
 
This of course takes into account the applying of logic to the mind of a man, who may in time, be found to have been responsible for 37 murders or more over a five year period, therefore you can possibly disregard everything you have just read as sheer madness. 

Incidentally Arthur Leigh Allen was living within this one mile radius at 32 Fresno Street, during the first two confirmed attacks at Lake Herman Road and Blue Rock Springs Park. His residence sits approximately 10 minutes north of the Springs Road and Tuolumne Street intersection.