The following is extremely speculative and probably way off base, but since it has never been suggested before (as far as I am aware), it is worth putting forward as a possible example of Zodiac piggybacking a crime unrelated to his murderous exploits.
The bodies of Dr. Victor Ohta (45) and his wife, Virginia (43), along with their two sons, Victor Taggart (11) and Richard Derrick (12), and secretary, Mrs Dorothy Cadwallader (38) were found murdered in the swimming pool of the residence. They had been callously executed.
Dr. Ohta had been shot in the back and under the arm, while the others had been shot in the back of the neck. It was literally a bloodbath. The victims had been bound and blindfolded with scarves before being murdered. The Ohta residence was then set on fire. When the fire crews arrived at the isolated estate they were hampered by Dr. Victor Ohta's Rolls Royce and Mrs. Dorothy Cadwallader's Lincoln Continental blocking the entrance.
Later that day Dr. Ohta's green Oldsmobile station wagon was discovered burnt out on railway tracks near Felton, approximately 18 miles northwest of the crime scene. Although not definitively linked to the other five murders, Thomas DeCecco (19), a service station attendant was found bound and shot in the head near Saratoga only hours after the initial crime, possibly bringing the victim count to six.
A typewritten note was discovered under the windshield wipers of Dr. Ohta's Rolls Royce. It stated "Halloween...1970. Today World War III will begin as brought to you by the people of the free universe. I and my comrades from this day forth will fight until death for freedom, against anything or anyone who does not support natural life on this planet. Materialism must die or mankind will." Signed "Knight of Wands, Knight of Cups, Knight of Pentacles, Knight of Swords."
John Linley Frazier was arrested shortly after the murders and was sentenced to death on November 29, 1971. However, in 1972 the death penalty was abolished in California and his sentence was commuted to life imprisonment. He committed suicide by hanging on August 13th 2009.
Dr. Victor Ohta was an eye surgeon (ophthalmologist), and six possible victims were reported in the newspapers (6 pairs of eyes). The skeletons on the card outer and inner also had the eyes highlighted in red, one in the form of a blindfold, in similar fashion to the victims thrown into the pool.
Zodiac researcher Tom Voigt 'floated' this idea on his message board in 2012: "I received an interesting observation of the Halloween card via e-mail recently -- it suggested the skeletons were meant to depict a water scenario, with the top skeleton being a diver (my guess would be the pumpkin representing swim trunks?) and the bottom skeleton floating under water, I'm guessing then the many eyes possibly representing bubbles?" What if the water was from the swimming pool at 999 North Rodeo Gulch Road.
The 'Halloween' card would emphasize four methods of death: By Fire, By Gun, By Rope and By Knife, three of which would feature heavily in the Ohta murders.
Had the Zodiac Killer read the coverage of the brutal murders at Sosquel and beyond, and fearing that his relevance was dwindling in the newspapers, used the crime of John Linley Frazier to piggyback himself back into prominence? If this was the case, unfortunately for him, nobody understood the connection, and the meaning of the 'Halloween' card was lost in translation. As an explanation for the October 27th 1970 correspondence, this is probably wide of the mark. It does, however, give us a flavor of some of the radical views that permeated California in the 1960s and 1970s, and the beginning of the end for the Zodiac Killer.