James Owen traveling at 40mph along Lake Herman Road to Humble Oil in Benicia on December 20th 1968, would cover 925 feet in approximately 16 seconds. Traveling at 30mph he would cover this distance in 21 seconds. This is the distance between the bottom of the hill looking up to the now infamous Lake Herman Road turnout. James Owen never reported seeing any headlights of a vehicle entering the turnout as he approached. If the Zodiac Killer had entered the turnout just prior to James Owen arriving at this position on Lake Herman Road, can we reasonably conclude that the moment Zodiac arrived in the turnout, his immediate actions were to pull up to the right side of the 1961 Rambler, exit his vehicle, fire two shots into the Rambler, approach its passenger side door, before summoning both David Faraday and Betty Lou Jensen from the Rambler, and then making David, Betty and himself completely vanish from the turnout before James Owen passed? The Zodiac Killer would have needed to achieve all these actions in marginally over 16 to 21 seconds. It simply isn't realistic.
So let us consider that James Owen was 60 to 90 seconds away from the turnout (or more) when Zodiac pulled up alongside the Rambler. Based upon the chain of events we have been sold, wouldn't we now have expected James Owen to see two bodies lying in the turnout? (with or without Zodiac's vehicle}. However, he saw nobody in or around the vehicles, or beyond the turnout. Therefore, if the Zodiac Killer entered the turnout that night with the express intention of extracting both David and Betty from the Rambler and killing them quickly, he can only realistically have entered the turnout moments before James Owen arrived. Let us consider a third option.
James Owen didn't recollect the passenger door of the Rambler being open when he passed the turnout - so if it wasn't open - then the Zodiac Killer must have closed it before Owen passed and re-opened it later - because this is how it was discovered by responding officers. If we look at the police sketches and this video, James Owen should have had a line of sight to the passenger door of the Rambler. While this version of events is possible, it sounds wholly implausible for numerous reasons.
Is it possible that the Zodiac Killer had already committed the murders and was heading back to Vallejo when James Owen saw his vehicle by the Borges Ranch? This was the extended police statement given by James Owen, that "just before he approached the scene, a vehicle passed him going in the opposite direction toward Vallejo. He could give no description of the vehicle. This occurred near the Borges Ranch". The person driving this vehicle had impeccable timing, yet never came forward. If the individual driving this car towards Vallejo wasn't the Zodiac Killer, then they could have seen the second vehicle and crime in progress at the turnout also. If this driver was the Zodiac Killer, then it's pretty obvious why he never gave a police statement.