The case for the hitchhiker being the murderer was considered on the basis of this line in the 1986 letter: "They were killed by a freeway. The Blue Meannies almost caught me". The idea being, the hitchiker reported the murders as an "accident" in a cat and mouse game with authorities. But how can we determine whether or not the hitchhiker was the author of the 1986 letter, or possibly the Zodiac Killer? The link between the 1986, 1987 and 1969 Zodiac communications strongly suggests one author responsible for all five letters, however, this doesn't tell us whether the hitchiker was a concerned citizen performing his civic duty, or somebody toying with the police, who failed to provide any details about himself - and has never been identified to this day.
The Sacramento Bee ran an article stating "Two victims, Choy Fow Saelee and Koy Ien Saechao, were found dead in their car by a hitchhiker about 6:30 am. Sometime later the hitchhiker reported what he had seen to authorities in Marysville". Marysville (or Marysville Police Department) is 67 miles north of the crime scene, and 18 miles further north from East Nicolaus, along California State Route 70.
The Sacramento Bee ran a much more comprehensive article and wrote "Police discovered the bodies, sitting upright in the front seat of the Mercury, after a hitchhiker told a Chico California Highway Patrol Officer he had witnessed a car wreck at the freeway interchange, Sgt. Bob Burns said". Chico is 90 miles north of the crime scene, a 90 minute car journey, and 49 miles from Marysville.
So, either the information given by law enforcement to the newspapers was wildly inaccurate, the newspapers had reported it incorrectly, or the hitchhiker traveled an extraordinary distance, contacting at least three police forces over a 90 mile journey. Had the latter been the case, the hitchhiker was either an extremely diligent and concerned citizen, or he was playing games in the aftermath of the murder, possibly writing "They were killed by a freeway. The Blue Meannies almost caught me" just two weeks later. The reported contacts with the hitchhiker were at least consistent with somebody traveling north along Highway 99 and California State Route 70, from Sacramento to Chico. Had the hitchhiker continued north, he would have arrived in Redding, California. To the west was the city of Eureka in Humboldt County.
Because we can confidently authenticate this communication to the Zodiac Killer, it leaves us with the possibility that the release of the Robert Graysmith book may have awoken the Zodiac Killer from his slumber. This crime didn't receive widespread coverage throughout California, so the Zodiac Killer must have been extremely fortunate to have stumbled across a crime that mirrored two of his previously claimed attacks, accompanied by a mysterious and elusive hitchhiker, only a matter of months after Robert Graysmith's Zodiac hit the bookshelves and placed the Zodiac Killer back into the spotlight. Or, it had rewoken his desire for murder once again - and he was responsible for the murders of Choy Fow Saelee and Koy Ien Saechao in the early morning of April 22nd 1986.