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Zodiac Killer Research

Original research and interpretive essays by T.C. ("SDS"), exploring the intersections of geography, language, and criminal history across the twentieth century. Each text is independently authored and first published here, tracing how infrastructure, media, and myth intertwine in the record of unsolved crime. Development of original CHS ("Contextual-Holistic-Systemic") data-driven model. © T.C. / Zodiac Research 2023-2025. All rights reserved. Citation or quotation permitted with attribution.

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Zodiac Letters 1_1969_7_31

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Zodiac Letters 2_1969_08_04

Vol. 1. Debut letter tone and writing for print

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Commentary vol. 1: The Joost Name and the Cartography of Power

Commentary_vol_1_The Joost Name and the Cartography of Power With this post I am opening a new section of the site — Commentary — a space for reflection and interpretation rather than primary analysis. Unlike the Crimes , Ciphers , or Letters pages, these essays will not aim to prove or disprove a specific event but to discuss the broader historical, linguistic, and infrastructural frameworks that surround the Zodiac material. The first commentary arises from Tom Voigt’s October 17, 2025, release of Paul Avery’s private communique to Sherwood Morrill, written on 17 November 1969, in which the Chronicle reporter referred to a “Joost suspect.” [1] The note, unpublished for more than half a century, has reignited debate on the message board of ZodiacKiller.com on Tapatalk [2]. Many commenters have tried to determine which individual Avery might have meant, often listing living members of the Joost family or their descendants. My own approach is different. I am less inte...

About this blog

Welcome to Zodiac Killer Research. A blog which serves as a collection of works, thoughts, and datasets about a series of murders attributed to the self-proclaimed "Zodiac". This unidentified white male adult operated in the state of California, USA, within the timeframe of 1968-1974 (consensus for canonical activity). He committed four attacks in different crime scenes in the North Bay Area, murdering five young civilians and seriously injuring two more, who thankfully managed to survive, in the period from December 1968 to October 1969. He wrote to the press from July 31, 1969 to (at least) July 8, 1974. He could be responsible for more murders and/or communications, within the "canonical timeframe", or even after. Some speculate - even before . Families mourned, law enforcement invested manpower, time and resources to follow any possible lead, journalists sought information. Books were eventually written, movies were shot, persons of interest were compiled, look...

Canonical cipher 3: Z13 vol.1. Entropy based solution of Z13

An entropy-based solution of the Z13 based on a cascade consideration of ciphers Comment: Originally proposed in May 2024 on Tom Voigt’s Tapatalk Zodiac Killer forum and message board, this solve has undergone revision that does not take away from the step-1 solution (Table III) nor the end solution (Table IV). The solution wishes to explain the process of step-2 better and contextualize with the solution proposed by Dr. Ryan Garlick. Moreover, it offers a step-3 for the validation of symbols order. Z13 has been considered time and time again as per its short length which does not allow for an inclusion (and therefore discovery) of an internal key. Various suggestions have been provided and various solutions have been proposed, including some very plausible and interesting solutions by zodiac researchers and cipher scholars in this forum, such as cipher (comment: SolidSnake1990) and rando . My approach, based on my signal processing/information theory background, is based ...