The only other time the Zodiac Killer mailed a cipher in connection with a brutal knife murder, was when he mailed the 148 character cipher shortly after the arrest and interrogation of Karl Francis Werner for the murders of Kathie Snoozy, Debra Furlong and Kathy Bilek on August 3rd 1969 and April 11th 1971. In the 148 character cipher the Zodiac Killer encrypted "I will skin three little kids and make a suit from the skin", and wrote "I will send a patch of human skin if their is some left over" in the message of the accompanying letter. Bearing in mind the killer removed Robert Salem's left ear and took it from the crime scene, I considered the possibility that the word "skin" may feature in the 13-Symbol cipher, alongside the word "satan" (or an extension of it), taken from the apartment wall. In other words, the encrypted message was related to the murder scene of Robert Salem. The dash after "My name is" in the April 20th 1970 letter, being the withheld name, with the 13-Symbol cipher being the message.
ROBERT SALEM-A ZODIAC MURDER?
A CONTEMPORARY CODE ON APRIL 20TH 1970
THE ZODIAC KILLER-DRIVEN BY DEVIANCY