What advances in DNA are possible in the near future to help capture the Zodiac Killer?

 

Possible advances in DNA technology in the near future (e.g., the next 5–10 years) could significantly aid in identifying the Zodiac Killer, whose case remains unsolved as of mid-2025. The Zodiac Killer is linked to at least five confirmed murders in the San Francisco Bay Area between 1968 and 1969, with the perpetrator taunting authorities via letters and ciphers. DNA evidence primarily comes from saliva on stamps and envelopes from these letters, yielding only a partial profile in 2002 that was insufficient for a full match or entry into databases like CODIS due to degradation, low quantity, potential contamination from handlers, and evidence mishandling. No confirmed DNA exists from crime scenes, and while groups like the Case Breakers have claimed suspects (e.g., Gary Francis Poste in 2023, with alleged partial DNA held by the FBI but not acted upon), official investigations by agencies like the FBI and SFPD maintain the case is open and unsolved.

Recent efforts, such as those by DNA expert Dr. Richard Green of Astrea Forensics (involved in analyzing Zodiac-related letters tied to a possible 1966 victim, though results pointed to a hoax), highlight how emerging tools could re-analyze existing samples or uncover new leads. Below is an outline of key near-future DNA advances relevant to cold cases like this one, based on developments from 2019–2025. These focus on handling degraded, low-quantity, or mixed samples, which are central challenges here. Each advance includes a description and an explanation of how it could help capture the Zodiac Killer.

• Investigative Genetic Genealogy (IGG) / Forensic Genetic Genealogy (FGG): This uses single nucleotide polymorphisms (SNPs) from DNA samples to search public genealogy databases (e.g., GEDmatch) for distant relatives (e.g., third or fourth cousins), building family trees to narrow suspects. Advances include whole-genome sequencing for remains and regulatory frameworks (e.g., Maryland’s 2021 law) to address privacy while enabling law enforcement use. Successful in over 100 cold cases since 2018, including the Golden State Killer (Joseph James DeAngelo, identified via discarded items matching crime scene DNA). If a fuller SNP profile can be obtained from the partial Zodiac saliva DNA (or untested letter fragments), it could identify relatives, leading to a suspect—even if deceased (the killer would be ~80–100 years old today). This has solved cases like the 1956 murders of Lloyd Duane Bogle and Patricia Kalitzke (via genealogy matching Kenneth Gould) and the 1970 murder of Nancy Marie Bennallack (identifying Richard John Davis).

• Next-Generation Sequencing (NGS) / Massively Parallel Sequencing (MPS): This enables detailed analysis of degraded or low-quantity DNA by sequencing additional markers (e.g., SNPs, microhaplotypes, full STR alleles, mitochondrial DNA). Tools like MiSeq FGx, ForenSeq kits, and nanopore devices (e.g., MinION) handle complex samples; revised guidelines (e.g., SWGDAM 2019) improve mitochondrial analysis. Portable sequencers are emerging for field use, with costs dropping and accuracy rising. It could re-sequence the degraded Zodiac stamp DNA to generate a more complete profile (beyond the 2002 partial STRs), allowing database uploads or genealogy searches. This is ideal for old evidence, as seen in solving the 1987 murders of Shannon Rose Lloyd and Renee Cuevas (via partial DNA family tree building to identify Rueben Smith).

• Enhanced DNA Recovery from Degraded or Touch Samples: Techniques for extracting DNA from challenging sources like rootless hairs, old saliva, or touched items (e.g., Astrea Forensics’ methods, optimized workflows for ammunition/clothing). Includes touch DNA transfer studies (DNA-TPPR) and shedder status analysis to interpret incidental contact. Zodiac letters/envelopes could yield better DNA via re-extraction, distinguishing the killer’s saliva from contaminants. Labs like Astrea have succeeded with similar degraded samples in cases like Gilgo Beach (tying Rex Heuermann via hair DNA) and the 1982 murder of Daralyn Johnson (using IBDGem software for comparisons).

• DNA Mixture Deconvolution and Probabilistic Genotyping: Software like STRmix, EuroForMix, and MPS-based tools (e.g., microhaplotypes, deep learning pipelines) separate mixed DNA profiles from up to 10 contributors, with single-cell analysis for isolation. If Zodiac samples are mixed (e.g., from multiple handlers), this could isolate the killer’s profile, as in the 1989 murder of George and Catherine Peacock (new tests on mixed blood identified Michael Louise).

• Forensic DNA Phenotyping: This predicts physical traits (e.g., eye/hair/skin color, age, ancestry, facial shape) via MPS and epigenetic markers (e.g., VISAGE tools, HIrisPlex-S system). Machine learning improves accuracy for pigmentation and biogeography. A phenotype from Zodiac DNA could generate a suspect sketch matching 1960s descriptions (white male, ~30–40, brown hair), narrowing leads or confirming claims like Poste (partial DNA allegedly held by FBI).

• Rapid DNA Analysis: Portable instruments (e.g., ANDE 6C, RapidHIT) provide profiles in <90 minutes from high-quantity samples, with research expanding to low-quantity/mixtures. It could quickly test any new Zodiac-linked evidence (e.g., recently ID’d remains of possible victims), accelerating comparisons to the partial profile.

These advances build on programs like the DOJ’s Prosecuting Cold Cases Using DNA (COLD) initiative, which funds re-testing. However, success depends on evidence quality, funding, and inter-agency cooperation—issues that have stalled the Zodiac case (e.g., alleged FBI inaction on Poste DNA). If applied, they could finally unmask the killer, as in similar unsolved cases resolved post-2018.