What we know is the time of the attack was estimated at 9.55 pm, but both Armond Pelissetti and Donald Fouke received the dispatch at the identical time, detailed at 9.58 pm. Their actions thereafter can be quantified fairly accurately. Firstly we will start with Donald Fouke, who was driving his patrol car in the vicinity of Presidio Avenue and Washington Street at 9.58 pm. This is how he described the events of that night: "We were patrolling the eastern side of the Richmond District, going northbound on Presidio Avenue, we had passed Washington Street when a broadcast came in of a shooting at Cherry and Washington Street. As we approached Maple Street I noticed on the north side of the street a white male adult."
This gives us a distance to the initial sighting of Zodiac- so all we need now is Donald Fouke's driving speed to work out how much time had elapsed when he made this sighting. Donald Fouke went on to say regarding his speed, "Well until I saw him probably 35 or 40 mph on a 25 mph street." This is now enough information to calculate fairly accurately how much time had elapsed since the broadcast at 9.58 pm.
At this point Zodiac is approaching the intersection. His traveling distance from the taxicab to this point is 242 meters, at an an average walking speed of 3.1 mph, would take him 175 seconds, or just shy of 3 minutes. This proves that at least on one occasion the Zodiac was not lying. In the 'Bus Bomb' letter he mailed on November 9th 1969 he stated "p.s. 2 cops pulled a goof abot 3 min after I left the cab. I was walking down the hill to the park when this cop car pulled up + one of them called me over." The distances and timeline match up perfectly for Donald Fouke and the Zodiac Killer to cross paths at exactly the point of the Jackson and Maple intersection, which both ultimately confirmed. This combined with the matching descriptions of the three teenagers and Donald Fouke, puts it beyond any reasonable doubt this was the Zodiac Killer, no matter what Armond Pelissetti stated in the documentary 'This is the Zodiac Speaking'.
After the meeting with Zodiac, Donald Fouke stated in the documentary 'This is the Zodiac Speaking' that he continued onward to the next intersection, which was Jackson and Cherry Street, turned south and met Armond Pelissetti, who was traveling up Cherry Street in pursuit of Zodiac. This course of events is actually impossible. The distance to this point in Donald Fouke's journey is 1,000 meters (0.62 miles)- allowing for his claim of briefly slowing down for roughly 10 seconds as he passed the suspect- it takes approximately 80 seconds to reach the upper limits of Cherry Street from the Washington and Presidio Avenue intersection. The time would now be 9.59:20 pm.
Remember, Armond Pelissetti received the broadcast at 9.58 pm, the same time as Donald Fouke. Cherry Street is 100 meters in length, so at an average walking speed, this would take approximately 1 minute to travel in its entirety. That means if Armond Pelissetti had started his journey up Cherry Street at 9.58 pm, he would meet Donald Fouke at 9.59 pm, 20 seconds quicker than 9.59:20 pm.
However, Armond Pelissetti only received the broadcast at 9.58 pm. Armond Pelissetti was close by and reacted traveling west on Washington Street and parked at the intersection of Washington and Cherry. He exited his vehicle and noticed three teenagers approaching the scene, so he ushered the kids back across the street to the alcove of their residence. At this point he was of the understanding he was looking for a negro male adult suspect. He went over to the taxicab and observed Paul Stine lying slumped over the front passenger seat with his head resting on the floorboard of the passenger side and was 99.9% certain he was dead. It is then he retook the description of the suspect. In the 2007 'This is the Zodiac Speaking' documentary he stated "it was then I was told it was a white male, I couldn't get to the radio fast enough at that point to let everybody else know. The kids had told me whoever had done this crime had left the cab, went out the door and seemed to be wiping the cab down and reaching into the cab and ambling or walking down Cherry Street in a northerly direction, kind of towards the Presidio. I walked that way myself, I did not run because there are innumerable alcoves and parked cars, so I went down following every technique I knew so I didn't get my head blown off."
This means one or other of the accounts in the documentary 'This is the Zodiac Speaking' is factually incorrect, and it happens to be that of Donald Fouke.
Armond Pelissetti needed a bare minimum of 3 minutes, likely 4 minutes, to reach the upper section of Cherry Street. So if this was where the two officers met up, and it only took Donald Fouke 80 seconds to reach this point, what was Donald Fouke doing for the other 2-3 minutes.
The 'Crimes of the Century' documentary in 1989 gives us our first clue. In this documentary Donald Fouke stated;
"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 explains clearly the missing 2-3 minutes, before Donald Fouke finally returned back to Cherry Street and met up with Armond Pelissetti. He was searching the area of West Pacific Avenue by the park. But what was he doing there. He was supposedly responding to an attack on Paul Stine at the intersection of Washington and Cherry Streets. So why was he heading away from the crime scene. Well, the Zodiac Killer may have an answer in the 'Bus Bomb' letter "p.s. 2 cops pulled a goof abot 3 min after I left the cab. I was walking down the hill to the park when this cop car pulled up + one of them called me over + asked if I saw anyone acting suspicious or strange in the last 5 to 10 min + I said yes there was this man who was runnig by waveing a gun & 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." Why would you be heading in the opposite direction to the crime scene, when a taxicab driver is being assaulted. The answer is- he was directed there by Zodiac- which perfectly explains the missing 2-3 minutes of the timeline.
The distance from the beginning of Donald Fouke's journey to Arguello Street is 1.16 km (0.72 miles). This would take, allowing for slowing down passing Zodiac, approximately 100 seconds (1 minute 40 seconds). That would mean Armond Pelissetti had given the updated broadcast to a white male 100 seconds after receiving the initial broadcast at 9.58 pm. In other words his actions were fairly swift.
Donald Fouke is now at Arguello Boulevard at 9.59:40.
If Armond Pelissetti met Donald Fouke at the north edge of Cherry Street, considering we calculated he needed a minimum of 3 minutes to reach this point from the initial broadcast time, then Armond Pelissetti from the time he updated the broadcast at 100 seconds, took 1 minute and 20 seconds to reach the north edge of Cherry. Considering he was proceeding very cautiously, and it takes 1 minute to walk at a normal walking speed, Armond Pelissetti actually only took 20 seconds longer than the average. It also meant Donald Fouke spent 1 minute 20 seconds traveling from Arguello Boulevard, into West Pacific Avenue, and back to Cherry Street, before they met up. This was his cursory search of the Presidio park area from the roadside edge, after being directed there by Zodiac. It is extremely likely Armond Pelissetti needed closer to 4 minutes to reach the top of Cherry Street, thereby allowing Donald Fouke an extra minute to search West Pacific Avenue and the area by Julius Khan playground.
When Donald Fouke was updated to the white male description at Arguello Boulevard, he, according to statements, traveled along West Pacific Avenue to the area of the Julius Khan Park, which is about 1 and half blocks further east of the Jackson and Maple intersection, where he stated he last viewed the Zodiac Killer heading towards. Strange that, because Zodiac stated in the Bus Bomb Letter about an alleged discussion with police and "I disappeared into the park a block + a half away never to be seen again."
Crucially however, the timeline of Donald Fouke described above, relied on his version of slowing down and passing Zodiac. Had he, as suspected, called Zodiac from the sidewalk and took his instruction of "yes there was this man who was runnig by waveing a gun," and the Zodiac directed them toward Arguello Boulevard, then his timeline would have been delayed by approximately 20-30 seconds. Nevertheless, the timeline remains perfectly viable, give or take a few seconds.
But the bottom line is- had Donald Fouke traveled straight to Cherry Street, as described in the documentary 'This is the Zodiac Speaking', then the whole timeline fails to work- proving it simply didn't happen that way.