In the late 1960s and the early 1970s, the San Francisco area was haunted by a single man who claimed responsibility for five murders and may have been involved with even more. The person identified himself as the Zodiac Killer - forging one of the most well-known serial killer identities ever. He first became known to the world after sending letters to local and regional newspapers, stating that he was the murderer that the police were searching for.

A distinct feature of most of his letters was that they were written as Zodiac Killer's cipher, requiring different investigation groups to work together to decrypt them. In total, four letters contained various types of ciphers. The first Zodiac Killer's cipher was solved just one week later. However, it took much longer than that to solve the rest.

With the recent news of an engineer and a business consultant having finally solved the last two Zodiac killer's ciphers, as well as the Zodiac Killer's identity confirmed after more than 50 years since the murders, let's take a look at the history of the infamous serial killer who became an indispensable part of American crime culture.

The Zodiac Killer's Letters

San Francisco Chronicle, San Francisco Examiner, and Vallejo Times received the first hand-written letter on August 1, 1969. The letter opened with the following sentence:

"Dear Editor: I am the killer of the 2 teenagers last Christmas at Lake Herman."

Next, to prove that he was the killer, he specified some of the details of the murder that were only known to the police. The rest of the letter consisted of threatening other attacks if the letters and the Zodiac killer's ciphers accompanied them were not printed on the front page of the newspapers. In addition, the letters also contained a symbol - a cross within a circle - that became synonymous with the killer.

On August 7, a follow-up letter would be received at the San Francisco Examiner, "Dear Editor, this is the Zodiac speaking" were the first words of the second letter. It was the first time the killer mentioned his name. In this letter, the now-named Zodiac Killer mocked the police for not finding out the meaning of his first cipher. Plus, he included more details about the murders to prove his credibility.

The first Zodiac Killer's cipher was cracked by high school teacher Donald Harden and his wife the next day. The 408-character cipher contained the motivation behind the killer's actions. He claimed that he liked killing because it was "so much fun" and that all that he killed would become his "slaves in the afterlife." Nothing was mentioned about the Zodiac Killer's identity, however.

After sending three additional ciphers and much more letters in an almost five-year period, the Zodiac Killer abruptly stopped communicating with the press. By then, the police still had not determined his identity, and he had become infamous among people of all ages and professions, with them sending countless fake letters claiming to either know the Zodiac or mimic his style of writing.

The Investigation Of Zodiac Killer's Cipher

Different police departments of the San Francisco Bay area started immediately working on Zodiac Killer's identity once they got hold of the first letter. Through analyzing the hand-writing and the efforts of private professional and non-professional investigators, the main suspect emerged. His name was Arthur Leigh Allen.

Allen, however, was never convicted. He was indeed the main suspect, but the police failed to present enough evidence to arrest him. The leading detective on the case, David Toschi, has stated:

"I knew it was him the moment he stepped through the door."

The police even searched his place on many occasions, even after his death, but were unsuccessful in determining that he was the Zodiac Killer.

Parallel to the investigation, the actual killer continued to mock the police in their failed attempts to find out who he was. Even so, by the final one of his letters, the infamous Zodiac Killer's cipher was still not cracked. According to the killer himself, determining what was written in the three documents was crucial because they contained his real name.

Even though the letters stopped, the official investigations were never closed. They continued with less and less progress. That is, until the past two years, when the remainder of the Zodiac Killer's cipher was cracked and, allegedly, his real identity was determined.

Zodiac Killer's Cipher Solved

The second Zodiac Killer's cipher was finally cracked in December 2020, about 50 years after being received in the newspapers. An international team of code-breakers managed to decipher a 340-character message that contained 63 unique symbols by the Zodiac Killer.

Thanks to the computer program of the team's Belgian programmer Jarl Van Eycke, the team was finally able to crack the message on December 3, after running more than 650,000 variations of the Zodiac Killer's cipher. The text opened with the sentence, "I hope you are having lots of fun trying to catch me," - referring to the police department's unsuccessful efforts in pursuing the killer.

This sparked a new wave of people who started working on the final two ciphers that were still not solved. Among them was a graduate of École Polytechnique and HEC Paris - France's top engineering and business universities, named Fayçal Ziraoui. The final two ciphers were nicknamed Z13 and Z32 - according to the number of characters each of them had. The difficulty in cracking these ciphers was exactly their shortness, and they possessed much fewer numbers than the previous two, making it harder to determine their meaning.

Ziraoui, however, managed the impossible. He altered the technique used to crack the first cipher back in 1969 and reapplied it to Z32. The results were fascinating. The decrypted message yielded a set of coordinates pinpointed at a school location near South Lake Tahoe. It made sense because the Zodiac Killer had threatened to "wipe out a school bus" - something he never actually did.

Z13, the final remaining cipher, began with an intriguing phrase written in English: "My name is…." The rest of the letter was encrypted. When he applied the same technique, he determined that the name of the Zodiac Killer was close to KAYR - an interesting detail because it resembled one of the suspects' names - Lawrence Kaye.

Kaye was a resident near South Lake Tahoe, and some officials did believe that he was the person they were searching for.

Ziraoui's findings were not officially acknowledged by neither the FBI nor the online forums dedicated to the Zodiac Killer. People who have been trying to solve the mystery were not entirely convinced that Ziraoui had managed to crack the code in such a short time.

Whatever the case may be, the Zodiac Killer's cipher remains one of the most intriguing mysteries.

Zodiac Killer's Identity

Another crucial development regarding the infamous serial killer occurred very recently, in October 2021.

A team of 40 former law enforcement investigators, journalists, and enthusiasts of the case claim that they have finally identified the Zodiac Killer. The group, called The Case Breakers, has also been involved with other popular mysteries like the D.B Cooper case and the vanishing of Jimmy Hoffa.

They believe Gary Francis Poste to be the Zodiac Killer's identity. The team says that Poste, who passed away in 2018, is linked to another murder in the 60s, which was neither claimed by the Zodiac nor is believed to have been him. In addition, they presented visual evidence that closely resembles the sketches of the killer that were made in the 60s.

All in all, while Gary F. Poste was the Zodiac Killer's identity has not yet been confirmed by the FBI. However, despite this, it caused another public upheaval and was talked about widely in the news and on Internet forums.

The Legacy Of The Zodiac Killer

The Zodiac has one of the most well-known serial killer legacies. Even though he has killed fewer people than some of his more violent counterparts, the Zodiac Killer's ciphers and the mystery of his identity have gained him a lot of popularity.

Most notably, David Fincher's star-filled 2007 movie Zodiac, which featured big-name actors such as Jake Gyllenhaal, Mark Ruffalo, and Robert Downey Jr., managed to encapsulate the tense atmosphere present at the time of his murders. The movie was critically acclaimed and is a classic when it comes to the works on the killer.

In addition to this, countless people are still working on determining the real identity of the Zodiac and deciphering his messages. The mystery surrounding his case is truly unmatched and has sparked the interest of many amateur investigators.