His four confirmed attacks were Lake Herman Road on 12.20.68, Blue Rock Springs 7.4.69, Lake Berryessa 9.27.69 and Presidio Heights 10.11.69. These four attacks were committed on a Friday, Friday, Saturday and Saturday respectively, all at the weekend, suggesting the killer may have had a standard 9-5 occupation from Monday to Friday, only committing his murders prior to a day of rest.
Serial killers often begin their crimes close to home in what is termed a 'comfort zone'. In other words, areas that are familiar to them, such as their leisure zones, their place of work, the location of friends and family, along with functional activities. But not too close to risk identification or draw attention to their home residence. Once a crime has been perpetrated the main objective of the criminal is to return home, or to relative safety. Killers will venture further away from their home base as they gain confidence, but generally not too far, as the least time they are traveling carrying the 'smoking gun' or harboring transfer from the crime scene, the better.
On the right is a map of the four crime scene locations and the traveling times to each from Benicia, as this area will now become the main focus of our attention as the likely residence of the Zodiac Killer.
If Benicia was his residence during the murders, then his first two attacks at Lake Herman Road and Blue Rock Springs Park would have been relatively close to home, but committed in isolated locations that served to protect his identity.
If he worked standard occupation hours and finished work on Friday at 5.00 pm, the 'least effort principle' would come into play.
Murder was on his mind, but having arrived home late afternoon or early evening, he conceivably wanted to travel the least distance possible, while still maintaining a reasonable 'buffer zone' to his residence.
His Saturday crimes of Lake Berryessa and Presidio Heights were considerably further, and being a rest day for the Zodiac Killer, the 'least effort principle' would be mitigated.
Now we will examine the possible movements of the Zodiac Killer after each crime to narrow down a location for his home residence.
Eyewitness testimony from the Lake Herman Road murders suggested a very small window of time that the Zodiac Killer had available to him, in order to escape detection, but one eyewitness, that of Stella Borges, was the most crucial of all. A second eyewitness James Owen passed the turnout at what was calculated to be 11.14 pm and he saw no victims lying on the turnout. Stella Borges however, in a revised timeline, passed the turnout at approximately 11.20 pm and saw both victims David Faraday and Betty Lou Jensen lying on the gravel turnout.
Based on this chain of events, the earliest the Zodiac Killer could have murdered the young couple and started to leave the turnout would have been 11.15 pm. Stella Borges, it was estimated left her ranch at 11.15 pm heading towards Benicia. She reported passing no vehicles en route. Therefore the Zodiac Killer could not possibly have headed towards Vallejo along Lake Herman Road. The only possible scenario using these timelines, is the Zodiac Killer headed in an easterly direction towards Benicia and towards the relative safety of home.
After committing two brutal murders, possibly covered in biological material from the close contact murder of David Faraday, the sound of at least ten shots on a still dark night, and almost certainly still in possession of a .22 weapon, it would have been unimaginably stupid and furthermore made little sense for the killer to head in the opposite direction to his home residence, thereby risking a prolonged period of detection, and in all likelihood ruling out Vallejo as a location point for Northern California's most elusive serial killer.
The attack at Blue Rock Springs was approximated no later than 12.04 am on the 5th July 1969, however the call the Zodiac Killer made to police dispatcher Nancy Slover at the Springs Road and Tuolumne Street payphone was logged at 12.40 am. This payphone was located only a 10 minute drive from Blue Rock Springs. So what had the killer done during this time period. It is highly unlikely he would have sat stationary in his car in the area, or outside the payphone for any prolonged period. After gunning down two people only 3.7 miles away, this would only have increased his risk of capture.
The Zodiac Killer had likely planned this phone call to police in advance of the crime- this was his agenda, although it carried greater risk. The payphone may have been chosen because it was known to the killer and not too close to where he lived.
He was familiar with Lake Herman Road, and in near isolation, free from prying eyes, it would have been a perfect disposal site for his weapon, particularly bearing in mind Lake Herman was situated near to his first murders. A journey from Blue Rock Springs to Lake Herman, with time spent to exit his vehicle, wipe down the weapon and toss the evidence into Lake Herman, before returning to the payphone at Springs Road and Tuolumne Street, would have taken approximately 30 minutes, and nearer the time of 12.40 am, the time the call was logged. Any stop by police now, would have held far less risk. He could equally have traveled straight home after the attack at Blue Rock Springs, disposed of any incriminating evidence, before returning to make the phone call.
In the phone call to police dispatcher Nancy Slover, the killer would announce his campaign of terror "I wish to report a double murder. If you will go one mile east on Columbus Parkway to a public park, you will find the kids in a brown car. They have been shot by a 9 mm Luger. I also killed those kids last year.... Good-bye".
After his third attack at Lake Berryessa he made a second phone call at 1231 Main St, Napa, heading in a southerly direction, a direct route back to the Vallejo and Benicia region, suggesting a return to the locale of his first two crimes. This was the first time the Zodiac Killer had traveled any great distance to perpetrate murder.
Is it possible a connection between Lake Berryessa and Lake Herman could be forged from a standpoint of recreation. Was the Zodiac Killer a keen fisherman in his spare time, hence his choice of remote areas that seemed to punctuate his early crimes.
His final confirmed murder was that of Paul Stine at Presidio Heights on October 11th 1969. This was in stark contrast to his previous attacks, taking place in a built up area with high risk. To commit such a brazen attack in a heavily populated location seemed on the face of it an unusual choice, which led to the idea the killer was very confident in these surroundings.
It is well documented that a large proportion of his mailed correspondence was postmarked San Francisco, indicating he may have likely worked in San Francisco, yet lived in the Vallejo or Benicia region.