To achieve this, the Zodiac Killer would had to have read the morning newspaper about Salem, create his letter in a short period of time, then mail the letter so it could be processed and stamped with a morning postmark. This would have made the code contained within the letter contemporary to the murder of Robert Salem (unless it was created in advance). The writing on the apartment wall stating "Satan Saves Zodiac" and the severing of Salem's left ear, led me to consider the possibility of the code reading "Skin A Satanist" or "Ate Severed Ear", which both fit seamlessly into the code. But these solutions would be more relevant to Stanley Dean Baker than the Zodiac Killer, with Baker branded a "hippie satanist" by the newspapers after he admitted removing victims body parts and eating them. However, I have come to the conclusion that both of these solutions to the Z13 are almost certainly incorrect. But what about the rest of the letter?
There is a good reason to believe the Zodiac Killer was responsible for making a phone call to the San Jose, California Highway Patrol on December 19th 1969. On this date, somebody claiming to be the Zodiac Killer followed up his threats on the lives of multiple cops in the December 16th 1969 "Fairfield letter", by making a phone call to dispatcher Shirley Searey of the San Jose Highway Patrol and stating "I am going to kill five of you officers and a family of five between now and Monday". This threat towards California Highway Patrol may be relevant to his wording in the April 20th 1970 letter, when he wrote "But there is more glory in killing a cop than a cid because a cop can shoot back". Two weeks before this letter arrived - and dubbed the "Newhall Incident" - was the the worst massacre of police officers in the 80 year history of the California Highway Patrol, and possibly the worst in American history. It changed police procedure forever thereafter— improved police training on how to approach a suspect, better weaponry, bullet proof vests — saving the lives of many police officers in the line of duty. It was the story of the bravery and sacrifice of four young CHP officers, and the story of a true American hero, a civilian bystander who risked his life under fire from gun toting suspects to try to save the life of a downed patrolman. On the evening of April 5, 1970, four CHP officers, Roger Gore, Walt Frago, James "Skip" Pence, and George Alleyn were brutally gunned down by two dangerous suspects in the lot of a Standard Service Station next to J's Coffee Shop on what is now the intersection of the Old Road and Magic Mountain Parkway in Valencia, California. Link SCV History.com.
The Zodiac Killer's wording of "But there is more glory in killing a cop than a cid because a cop can shoot back" on April 20th 1970 - bearing in mind the previous threat on five CHP officers on December 19th 1969 - could have been inspired by the wall-to-wall newspaper coverage of the "Newhall Incident" on April 5th/6th 1970. In Zodiac's letter, there was also the reference to the murder of San Francisco police officer Brian McDonnell on February 16th 1970, who suffered devastating and sadly fatal injuries two months earlier, when a bomb packed with heavy industrial fence staples exploded on an outside ledge of Park Police Station in the Upper Haight neighborhood.
Whether this historical case was mentioned in the newspapers to some degree in relation to the Brian McDonnell murder is unknown - but if it was featured and noted by the Zodiac Killer, the sentence of "there is more glory in killing a cop than a cid because a cop can shoot back" would certainly have more meaning with respect to the April 20th 1970 communication. So, did the "Newhall Incident" or the murder of Sergeant Lacey (or both) have any role in the use of this phrase on April 20th 1970, or can we attribute pure coincidence to the wording chosen by the Zodiac Killer in this instance.
The headline of the Desert Sun newspaper on February 17th 1970, covering the murder of Brian McDonnell, read "Haight Ashbury Police Station Rocked By Bomb. Six Officers Injured In Blast Showering Big U-Shaped Staples". The Zodiac Killer would seemingly use this headline, and capitalize and emphasize the word "Blast" when creating his Dragon card on April 28th 1970, stating "I hope you enjoy yourselves when I have my Blast"..He would repeat the word "blast" on the card inner, stating "If you don't want me to have this blast you must do two things". It is clear that the Zodiac Killer invariably created his communications with previous newspapers being the inspiration, so I would be extremely grateful if anybody with a newspapers.com subscription could search for any mention of Sergeant Joseph Lacey in respect to the murder of San Francisco police officer Brian McDonnell on February 16th 1970. Thank you.