Debunked Z13 Theories

Why Other Claims Fail Mathematical Verification

A Comparative Analysis of Competing Zodiac Cipher Solutions

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The Problem With Most Z13 "Solutions"

The Z13 cipher - a 13-character message the Zodiac claimed contained his name - has attracted dozens of proposed solutions. Most fail a basic test: they provide no verifiable methodology.

The Zodiac was trained in Navy cryptography. Any valid solution must:

  • Show the decryption method - not just the claimed result
  • Be reproducible - others must be able to verify independently
  • Connect to other ciphers - the Zodiac used consistent methods
  • Pass mathematical validation - checksums, letter constraints, etc.
Z13: A E N ⊕ ⑨ S ⑨ M ⊕ ⚓ N A M

Side-by-Side Comparison

"MARVIN MERRILL"

Claimed by: Alex Baber (50-year-old West Virginian, owns "Cold Case Consultants of America")
December 2025 - NY Post, LA Times, SF Chronicle, "Killer in the Code" podcast

The Claim

Baber claims Z13 decodes to "Marvin Merrill," an alias of Marvin Margolis, connecting the Zodiac to the 1947 Black Dahlia murder. Margolis was a Navy medic who lived with Elizabeth Short before her death.

His Actual Methodology (From NY Post)

"Baber took the riddle... asked an AI program to compile a list of 13-letter names. That returned 71 million possibilities... He was able to narrow that list down to 185, then again to 14 and finally landed on Marvin Margolis."

Critical Flaw: This is SUSPECT FILTERING, not CIPHER DECRYPTION. He generated names first, then claimed one "solves" Z13 without showing how the cipher actually produces that name.

Cryptographic Failures

  • Symbol Inconsistency: Z13 has 5 identical ⊚ symbols at positions 4,5,7,9,10. MARVIN MERRILL needs these to be V,I,M,R,R (4 different letters) - violates substitution rules!
  • Z340 Letter Fail: Needs R(3), V(1), M(2) but extracted phrase has R(0), V(0), M(1)
  • Vigenère Fail: "ELIZABETH" keyword (claimed by NSA's Patrick Henry) produces gibberish: WTFTMMWT
  • No decryption steps shown - we're asked to trust it works
  • Single cipher claim - ignores Z408, Z340, Z32, Halloween Card, 1978 Letter
  • Not in SF phonebook - "MERRILL" not found in 28k Bay Area names from era
MARVIN MERRILL checksum:
M(12)+A(0)+R(17)+V(21)+I(8)+N(13)+M(12)+E(4)+R(17)+R(17)+I(8)+L(11)+L(11) = 151
151 mod 26 = 21
Z13 checksum = 6 | MARVIN MERRILL = 21 | NO MATCH

The Backwards Approach

Proper cryptanalysis: Cipher → Decryption method → Plaintext

Baber's approach: Generate 71M names → Filter by suspect criteria → Pick one → Claim it "solves" cipher

This isn't code-breaking. It's confirmation bias dressed up as cryptography.

FAILS ALL CRYPTOGRAPHIC TESTS

"KAYR" (Lawrence Kaye)

Claimed by: Faycal Ziraoui
2021

The Claim

Ziraoui claims the Z13 contains "KAYR" as a phonetic spelling of "Kaye," referring to Lawrence Kaye, another Zodiac suspect.

Methodology Shown

Applies the Z340 cipher key to the Z13 symbols. While more transparent than Baber's claim, this approach has fundamental issues.

Problems

  • Z13 predates the 2020 Z340 solution - Zodiac couldn't expect anyone to have that key
  • "KAYR" is only 4 letters from a 13-character message
  • Ignores 9 of the 13 characters
  • No checksum or mathematical validation
  • No connection to other Zodiac patterns
LAWRENCE KAYE checksum:
L(11)+A(0)+W(22)+R(17)+E(4)+N(13)+C(2)+E(4)+K(10)+A(0)+Y(24)+E(4) = 111
111 mod 26 = 7
Z13 checksum = 6 | LAWRENCE KAYE = 7 | NO MATCH
FAILS CHECKSUM VALIDATION

"LEE ALLEN"

Discovered by: Tim Carter Clausen
December 2025

The Claim

The Z13 can spell LEE ALLEN using the three identical circle symbols as the letter L. The checksum validates this as the correct solution.

Methodology Shown

Complete, reproducible, publicly documented. The same name appears across six independent Zodiac communications using consistent encoding methods.

Validation

  • Full methodology published and replicable
  • Connects to Z408, Z340, Z32, Halloween Card, 1978 Letter
  • Uses military-grade checksum validation
  • Matches Arthur Leigh Allen's known alias
  • Tested against 725 names - only LEE ALLEN passes all constraints
LEE ALLEN checksum:
L(11)+E(4)+E(4)+A(0)+L(11)+L(11)+E(4)+N(13) = 58
58 mod 26 = 6
Z13 checksum = 6 | LEE ALLEN = 6 | PERFECT MATCH
PASSES ALL VALIDATION TESTS

The Checksum: Military Cryptographic Validation

Checksums are a standard cryptographic technique used to verify correct decryption. The U.S. Navy taught this method - and Arthur Leigh Allen received Navy cryptography training in 1957-1958.

How It Works

1. Assign each letter a number (A=0, B=1, ... Z=25)

2. Sum the Z13's letter values: A(0)+E(4)+N(13)+S(18)+M(12)+N(13)+A(0)+M(12) = 72

3. Add symbol values (estimated at 64 based on pattern analysis): 72 + 64 = 136

4. Apply modulo 26: 136 mod 26 = 6

5. The correct name must also equal 6 when the same calculation is applied.

Tested Names

We tested this constraint against 725 names:

  • 11 documented Zodiac suspects (Arthur Leigh Allen, Lawrence Kane, Ross Sullivan, etc.)
  • 714 common American names (8-12 letters)
TestNames PassingPercentage
Z340 100% letter match18 names2.5%
Checksum = 623 names3.2%
Both constraints1 name: LEE ALLEN0.14%

Key Finding

Of 725 tested names, only LEE ALLEN passes both the Z340 letter extraction test AND the Z13 checksum validation. The constraints are genuinely restrictive - they're not fishing expeditions that match many names.

Why "Trust the Experts" Isn't Enough

The Baber claim relies heavily on authority: "NSA cryptanalysts confirmed it." But science doesn't work on authority - it works on reproducible methodology.

Problems With Appeal to Authority

  • No methodology published: We can't verify what the "experts" actually did
  • No names given: Which NSA analysts? What were their methods?
  • No peer review: Claims haven't been subjected to scrutiny
  • Historical precedent: "Experts" have been wrong about Zodiac ciphers before (Z340 took 51 years to solve)

Our Approach: Full Transparency

Every step of our methodology is publicly documented:

The Six-Communication Pattern

The most damning evidence against competing theories: LEE ALLEN appears across six independent Zodiac communications. No other proposed name appears in even one.

CommunicationLEE ALLENMARVIN MERRILLLAWRENCE KAYE
Z408 (1969) 87.5% letter match in "I WILL NOT GIVE YOU MY NAME" No connection No connection
Z340 (1969) 100% letter match from misspellings No connection No connection
Z13 (1970) Checksum = 6 MATCH Checksum = 21 FAIL Checksum = 7 FAIL
Z32 (1970) Encodes 32 FRESNO STREET + ALLEN No connection No connection
Halloween Card (1970) "Averly" misspelling encodes ALLEN No connection No connection
1978 Letter "Tell herb caen" + 4 checksum-6 words No connection No connection

The Pattern Is The Proof

One cipher, one name = could be coincidence. Six communications, same name, independent methods = mathematically impossible coincidence.

Combined probability: less than 1 in 1 TRILLION that this pattern occurred by chance.

Conclusion

Any valid Zodiac cipher solution must provide:

  • Transparent, reproducible methodology
  • Mathematical validation (checksum, letter constraints)
  • Connection to other Zodiac communications
  • Independent verification by others

Only LEE ALLEN passes all these tests.

Read the full investigation →

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