The distance from the steps at 3712 Jackson Street to the corner of Maple Street is 98 feet, so if both accounts were to have happened, then the patrol car would have to be stationary or near to it. A version of events could be argued where Donald Fouke is approaching Zodiac in his patrol car, spots the suspect, who in turn feigns to enter a residence - Donald Fouke then pulls up and questions the man, who directs them away with a story. As the patrol car pulls away a certain distance, the suspect re-enters the sidewalk thus catching the police officers attention in their rear view mirror as he proceeds onward towards the corner of Maple. This is the only way both accounts can be justified.
This encounter at 3712 Jackson Street would have occurred 862 meters from the point Donald Fouke received the initial broadcast at 9:58 pm on Presidio Avenue, taking approximately 1 minute duration, traveling at 30 mph. This means the Zodiac left the crime scene at 9:56 pm, taking 3 minutes to reach 3712 Jackson Street, something he confirmed in the 'Bus Bomb' letter mailed a month later. It has been previously noted that Donald Fouke could not have turned directly south along Cherry after this encounter with Zodiac, because in doing so he would arrive at the top of Cherry to meet Armond Pelissetti in approximately 70-80 seconds (possibly closer to 2 minutes had he stopped Zodiac), and something that was unattainable by Pelissetti from his accounts after arriving at the crime scene. Armond Pelissetti needed at least 3-4 minutes to achieve this meeting with Donald Fouke, a feat only achievable if Donald Fouke took a diversion.
In the 1989 Crimes of the Century documentary he gives us a clue, stating "We proceeded on Jackson Street towards Arguello continuing our search, as we arrived at Arguello Street the description of the suspect was changed to a white male adult, believing this suspect was possibly the one involved in the shooting we entered the Presidio of San Francisco and conducted a search on West Pacific Avenue, the opposite side of the wall and the last direction we observed the suspect going, we did not find the suspect". This account tallies nicely with his 2007 documentary account of "We turned around to get to the Presidio, and my reasoning on that, was because turning down Maple would lead through the Presidio wall directly into Julius Khan playground, which had a lot of foliage. So we turned and went down looking for the alleged suspect in the area of Julius Khan playground. Nothing was observed". The only difference, in that the events described in the first statement would have to have occurred before the meeting with Armond Pelissetti. However, what was his reasoning in heading to Arguello Boulevard, away from the crime scene he was supposed to be heading towards. Either he had been directed there by Zodiac, or he had acted on impulse, his suspicions aroused after seeing the suspect change direction, heading from the stairwell into Maple St after he pulled away in his patrol car. But this detour towards the Julius Khan playground is important, regarding the sighting of a man 'running into the Julius Khan playground' after the murder of Paul Stine and reported in the October 12th 1969 edition of the San Francisco Chronicle - but not for the reasons you may think.
This account, coupled with the San Francisco Chronicle article and Donald Fouke's directional movements that night of "we turned and went down looking for the alleged suspect in the area of Julius Khan playground. Nothing was observed", appears to center the focus squarely over Julius Khan playground. Even the Zodiac Killer alluded to entering the park at Spruce Street, when he remarked in the 'Bus Bomb' letter "the cops peeled rubber + went around the corner as I directed them + I disappeared into the park a block + a half away never to be seen again". But how did it come to pass that possibly several neighbors happened to spot the Zodiac Killer entering the playground at just gone 10.00 pm at night, with their curtains likely drawn? Well, Officer Donald Fouke may be responsible for the sighting, even though he observed nothing.
After the meeting with Zodiac at 3712 Jackson Street, the journey westwards for Donald Fouke to Arguello Boulevard and eastwards along West Pacific Avenue to Julius Khan playground is 810 meters (1/2 mile), taking approximately 1 minute traveling at 30 mph. For Zodiac, the journey eastwards to Spruce Street from 3712 Jackson Street is 180 meters (0.112 miles). So, assuming he picked up his walking speed to 4 mph after giving Donald Fouke and Eric Zelms the runaround, he would arrive somewhere in the vicinity of the Jackson and Spruce intersection in 1 minute 40 seconds. Assuming Donald Fouke and Eric Zelms arrived in 1 minute and performed a cursory inspection of the Julius Khan playground and vicinity, then turned around, the Zodiac Killer would be just arriving as they were leaving. Once the patrol car had headed into the distance, Zodiac seized the opportunity of retreat into the playground and 'dense foliage'.
If this sighting is correct, detailing a near perfect description of the killer, then this opens up further avenues, but unfortunately closes others. It would appear to suggest it highly improbable for Zodiac to have parked a getaway vehicle somewhere close to the Jackson/Maple or Jackson/Spruce intersection. Why would a killer in urgent need to flee the area, bypass his vehicle in preference to hiding in the vicinity of Julius Khan playground? Furthermore, a vehicle parked exposed further down Jackson Street even more of a stretch and seemingly of greater risk. On the other hand, a vehicle or residence located to the east of the Presidio Park is not without merit, with the park providing the cover of dense foliage and a distinct barrier of separation from the locale of the crime scene and search area - that fanned out across the park from north to south, and west to east.
The options appeared limited. The Zodiac, had he entered the park, would naturally move away from the activity, that included the search dogs barking: "The detectives heard from neighbors that a stocky figure was seen dashing across Julius Khan playground and into the dense undergrowth of the Presidio. The dog patrol units, seven of the best search dogs in the country, gathered at the front entrance of the Presidio". The Zodiac would goad the police on November 9th 1969 with the claim that "The dogs never came with in 2 blocks of me + they were to the west." Had this been the truth, the Zodiac had clearly moved in an easterly direction after entering the park, moving down to somewhere opposite Laurel Street or beyond - and to an area of very dense coverage. See here.
It is highly unlikely the Zodiac Killer remained in the park for long - the search, he knew was intensifying, and the dog units had been deployed with his options narrowing. There may be one final clue as to his exit strategy and direction, as he continued eastwards towards Presidio Boulevard. In the 'Bus Bomb' letter mailed on November 9th 1969, he would say one last thing about his excursion into the park, stating "then the motor cicles went by about 150 ft away going from south to north west". It is only supposition (as is the entirety of this analysis), but had he arrived close to Presidio Boulevard at this juncture, waiting for his moment to escape the Presidio into the Cow Hollow region on the eastern fringes, it can be seen here on Google Maps, that the motorcycles circling the park perimeter would be approximately "150 ft away going from south to north west". They pass by and the Zodiac is gone.
The only question left to ask is; was this improvisation on behalf of the Zodiac Killer, triggered by the three teenagers sighting and subsequent close shave with Donald Fouke and Eric Zelms, or was this escape route planned in advance? The answer as yet is undetermined, but it reminds me of youtube/4OAFtr-ciQE?t=7m37s .
'The greatest trick the devil ever pulled was convincing the world he didn't exist. And like that he's gone'.