This mental map was considered in the article Seventy One Days of Terror from October 11th 1969 to December 20th 1969, analyzing confirmed and unconfirmed letters, phone calls, murders and proposed murders during this time period. It became apparent that the locations targeted during this period, that included Sacramento, Fairfield, Vallejo, Oakland, San Francisco, Palo Alto and San Jose, all have Interstate 80 and U.S. Route 101 running directly through them. This may give us a clue to the areas where the Zodiac Killer was most comfortable. If he frequented these areas regularly in his profession, then this could very well influence the newspapers he read and the stories he became interested in. The case of murder victim Reet Jurvetson in a previous article, another example of a crime conforming to the above criteria. He may not have murdered this young woman, but was familiar with the area in which she was murdered, which ultimately governed his decision to choose her as victim number eight - allied to his new found fascination of knife crime. She too was brutally stabbed 157 times and unceremoniously dumped down a ravine off Mulholland Drive in Los Angeles. Her body was discovered just 2 miles from U.S. Route 101.
On April 20th 1970 he was claiming a victim count of ten - so if we are to determine the murder victims or proclaimed murder victims of the Zodiac Killer, then we must take all of the above into account. Based on three of the four attacks to date, victims nine and ten may have been a couple. They would have been murdered between December 20th 1969 and April 20th 1970, in a non-sexual attack that involved numerous knife wounds. It is also critical (whether the Zodiac Killer was responsible or claiming to be the responsible) that they would would be found close to Interstate 80 or U.S. Route 101.
On February 22nd 1970, John Franklin Hood (24), who had served decorated time in Vietnam in the 64th Armoured Division and Sandra Garcia (20), who worked in the California Department of Motor Vehicles, were discovered brutally stabbed on a beach close to Santa Barbara Cemetery and East Cabrillo Boulevard. This crime in some ways mirrored the stabbings at Lake Berryessa on September 27th 1969, with Sandra Garcia receiving the brunt of the vicious attack. The beach where their bodies were found, lies only 500 meters from U.S. Route 101. The mental map of the Zodiac Killer is starting to take shape.