ZODIAC DNA: The Magic Bullet

News that forensic genealogy led to the arrest of the infamous “Golden State Killer” inspired speculation that the same methods could be used to identify the elusive “Zodiac” killer. Previous attempts to obtain a complete genetic profile from DNA found on the stamps or envelopes sent by the killer had failed, but renewed efforts to uncover Zodiac DNA have created hopes that modern science will provide instant answers. Television shows such as CSI, Criminal Minds, and more have convinced many viewers that DNA is crime-fighting magic but the real-world applications are more complicated.

The Golden State Killer was identified through a complex process which included DNA testing, searches of DNA ancestry databases, forensic genealogy, exhausting research of public records, and old fashioned detective work. Investigators began with a sample of DNA taken from semen left by the killer at the scene of a 1980 murder in California. The genetic profile was then uploaded into the ancestry database known as GEDmatch and some distant cousins related to the killer were identified by familial DNA. Once the distant cousins were identified, these individuals were traced back to a common ancestor, the great-great-great grandparents of the Golden State Killer. From there, investigators assembled 23 family trees listing all of the descendants of the great-great-great grandparents. From that list, investigators narrowed the search to males who matched specific criteria: the correct age range, physical description, background and geographical location corresponding to the profile of the killer. After eliminating family members who did not match that criteria, investigators further narrowed the field of potential suspects to 5 men. One of those men was named Joseph James DeAngelo, and his profile was by far the most intriguing. Investigators set up surveillance of DeAngelo and followed the suspect until he discarded items in public spaces which could be used to obtain DNA. A comparison proved that DeAngelo’s DNA matched the Golden State Killer’s DNA. A second sample was obtained and the second comparison matched. According to some reports, at least one of the DeAngelo DNA samples was obtained from a discarded tissue. DeAngelo was subsequently arrested after investigators obtained a warrant to search his home.

Despite the complex process behind the seemingly easy identification of the Golden State Killer, many people seem convinced that authorities simply checked a DNA ancestry website, found the killer’s profile, name, and home address, and then arrested him, but forensic genealogy did not identify the killer. Joseph DeAngelo’s DNA was not listed in the ancestry database, but the DNA of his distant relatives was among the approximately 950,000 genetic profiles contained in the GEDmatch records. Once the distant relatives were identified, investigators had the overwhelming task of essentially accounting for the entire family line over a century in order to find the needle in the haystack and catch the killer.

Any attempt to catch the Zodiac using similar methods would require a substantial DNA sample. Some ancestry databases such as Ancestry.com and 23andMe require DNA samples taken only from saliva. Any DNA found on Zodiac communications would most likely consist of saliva, either on the envelope flaps or stamps used by the killer to send his messages, but this profile could not be used to search Ancestry.com or 23andMe databases. The Vallejo police department recently submitted two Zodiac envelopes for DNA testing, and a substantial DNA profile could be used to search ancestry databases for the Zodiac or his relatives. Yet investigators would most likely face the same challenges in the Golden State Killer case, specifically the exhaustive search through public records to track an entire family group. Narrowing the search to male relatives who matched the Zodiac criteria and would be likely suspects, investigators might choose to surveil individuals in question and surreptitiously obtain a sample of  DNA from personal items discarded in public. A comparison could prove that an individual had licked a Zodiac stamp or envelope, but proving that the person who did so was also the killer would require more evidence to establish a solid connection.

The Zodiac envelopes which contained pieces of a victim’s bloodstained shirt had been tested for DNA, and new testing could produce a complete genetic profile. This evidence would prove that the person who licked the stamp or envelope was in contact with evidence directly linking the killer to the crime. Anyone who licked the stamp or the envelope was most likely aware of the envelope contents and was therefore linked to the murder and the murderer. Matching an individual’s DNA to the DNA on a Zodiac envelope may not be sufficient to declare the case solved. Investigators might seek handwriting, fingerprints, and other evidence which could establish a link between an individual and the Zodiac crimes. The Zodiac took the car keys, wallet and shirt of his last known victim, and, if alive today, he may still possess these items along with the costume worn during the Lake Berryessa attack and other evidence. A DNA match to DNA from a Zodiac envelope could help investigators obtain a search warrant which might uncover this and other evidence which could close the case.

Absent some confirming evidence, DNA would not be sufficient to call a press conference and publicly identify anyone as the Zodiac. Libel and slander laws could prevent authorities from making declarations connecting any suspect to the Zodiac crimes without solid evidence to back up any accusations, implied or direct. The complexities of various scenarios reveal the potential problems in any effort to publicly identify a suspect. A living suspect could sue any police department or reporter who made unsubstantiated accusations, and the suspect would undoubtedly hire an attorney to fight any charges in court or in the media. Authorities could not prosecute a living suspect without substantial evidence linking the suspect directly to the crimes. Accusing a dead suspect would pose other problems, such as the lack of genetic material necessary to conduct DNA comparisons to prove a match to Zodiac DNA, or, uncooperative relatives who refuse to provide any DNA for any comparisons. In most instances, authorities would be reluctant to publicly name a deceased suspect without substantial evidence. Linking a suspect directly to the murders would require more than DNA. Some observers may be satisfied by a DNA match to a DNA stamp or envelope, especially if the envelope contained a piece of the victim’s shirt. A suspect would have difficulty explaining the presence of his DNA on the envelope, although he might possibly claim that he licked the envelope for someone else and was unaware of the contents. Implausible explanations would do little to convince most observers and the suspect would undoubtedly face continuing scrutiny. Investigators will require substantial evidence to close the case, so the presence of DNA on a Zodiac communication may not be sufficient, especially if any suspect identified by that DNA decides to fight the issue in a court of law.

Many theorists are unlikely to accept the results of any DNA comparison which identifies the Zodiac as someone other than their pet suspect or excludes their suspects. Others who claimed to have identified the Zodiac hope that news of DNA testing or rumors of problems with previously obtained genetic profiles can somehow rehabilitate their weak and unsubstantiated theories. When confronted about the lack of credible evidence implicating their suspect in the Zodiac crimes, many theorists will respond by complaining, “Well, you can’t prove my suspect isn’t the Zodiac.” This complaint is then followed by demands for DNA tests to resolve the issue and an attempt to redirect the burden of proof onto those who are not convinced theorists have identified the killer.

Most of the individuals known as “suspects” in the Zodiac case are not considered viable suspects by investigators, and many were dismissed or excluded by law enforcement long ago. Larry Kane was excluded on the basis of handwriting experts who determined that he did not write the Zodiac letters and the negative results of fingerprints comparisons. Retired San Francisco police lieutenant Tom Bruton stated that Kane was also excluded by DNA comparison. Other suspects were also excluded by handwriting, fingerprints, DNA and other means, yet some of these men remain popular suspects in public forums.

The so-called “prime suspect,” convicted child molester Arthur Leigh Allen, was originally investigated because an estranged friend claimed that Allen had confessed his intention to commit crimes and write letters using the name “Zodiac” before these events actually occurred. Police investigated and eventually searched Allen’s trailer, and investigators also asked Allen’s brother to search the suspect’s property in the home of their parents, but no evidence implicated Allen in the Zodiac crimes. Suspected Zodiac fingerprints did not match Allen’s fingerprints, handwriting experts concluded that Allen did not write the Zodiac letters, and Allen did not match descriptions of the killer provided by eyewitnesses. The lack of credible evidence implicating Allen directed investigators in search of other, viable suspects, and the investigation of Allen effectively ended in the mid-1970s. Later, other evidence indicated that Allen was not a viable suspect. The estranged friend who first accused Allen changed, embellished and invented stories. A police officer who saw the Zodiac provided a description of the killer which could not match Allen. A “writer’s palm print” found on a suspected Zodiac letter did not match Allen’s palm print and none of the suspected Zodiac fingerprints matched Allen’s fingerprints. A surviving Zodiac victim claimed that Allen was the man who shot him in 1969, but the identification two decades after the shooting was problematic at best. The witness originally provided a description which did not match Allen in 1969. The witness also indicated that the shooter had a face similar to another individual in a collection of photographs provided by police, a strong indication that the “identification” of Allen was not reliable, and police did not consider the witness identification valid. Investigators lacked the evidence to press charges against Allen and prosecutors could not win a conviction without substantial evidence connecting Allen to the Zodiac crimes. In the late 1990s, San Francisco police obtained DNA from a suspected Zodiac letter, and the DNA did not match Allen’s DNA. In 2002, San Francisco police obtained another partial genetic profile from another suspected Zodiac communication, and that DNA did not match Allen’s DNA. Several years later, Vallejo police submitted evidence to a lab for testing, including two envelopes which contained some of the first letters sent by the killer in July 1969. The results reportedly revealed a partial genetic profile which was not sufficient to positively identify anyone as the Zodiac. According to some reports, this DNA profile did not match Arthur Leigh Allen. None of the evidence obtained from any of the suspected Zodiac communications has matched Allen, including handwriting, fingerprints, palm prints, and DNA. To his accusers, the lack of any evidence linking Allen to the crimes is proof that he was a criminal genius. To most observers, the lack of any credible evidence linking Allen to the crimes, after almost five decades of investigation, speaks volumes on the question of his possible guilt or innocence. Allen may have been the Zodiac but the evidence does not indicate that he was the Zodiac.

Rumors circulated that the partial genetic profile obtained by the San Francisco police in 2002 was somehow invalid or unreliable, leading to claims that Allen was somehow a “prime suspect” again simply because some people questioned the DNA evidence which did not match Allen’s DNA. This logic depended on the notion that Allen was discarded as a suspect because his DNA did not match suspected Zodiac DNA and not because decades of investigation failed to produce any credible evidence linking Allen to the Zodiac crimes. San Francisco police virtually abandoned Allen as a suspect in the mid-1970s, more than two decades before any suspected Zodiac DNA did not match Allen’s DNA. The notion that Allen should be viewed as a prime suspect was not based on facts or reality. Thanks to the books written by former San Francisco Chronicle cartoonist Robert Graysmith and the film adaptation featuring the “prime suspect” many people remain convinced that Arthur Leigh Allen must be somehow connected to the Zodiac crimes, as the lone killer or working with accomplices. In a far more likely scenario, in keeping with the known facts and the evidence, Allen was simply the wrong man. The Vallejo Police Department still considers Allen a suspect but also entertains other theories and investigates other suspects. The agencies involved in the Zodiac investigations continue the search for the killer precisely because investigators are not convinced that Allen was the Zodiac. New DNA evidence could implicate Allen but the possibility exists that the killer could be someone never-before named as a suspect.

Identifying the Zodiac through DNA testing of suspected Zodiac communications, forensic genealogy, and other avenues of investigations depends on many factors. Authorities must obtain a substantial genetic profile in order to facilitate the forensic genealogy research. The authorities must search a database which contains the DNA information from at least one person in the family lineage of the Zodiac. Investigators must then create a list of everyone in that family and identify any and all male members of the family who are the right age, description, background and geographic history as the Zodiac. Investigators must then track down and account for all of those potential suspects until they can locate the Zodiac. Investigators must then obtain the suspect’s DNA and compare that evidence which the Zodiac genetic profile. Once a match is found, investigators must then obtain other evidence through further investigation and/or search warrants. Investigators must then connect the killer to the crimes with the available evidence, and that evidence must be sufficient to win a conviction in a court of law. Many problems can arise: authorities might be unable to obtain a substantial DNA profile from suspected Zodiac communications; the DNA database may not contain the genetic information from anyone in the killer’s family; investigators may be unable to accurately identify all potential suspects in the family line; information about a potential suspect may be unavailable or incomplete; DNA of a deceased suspect may be unavailable and living family members may be unwilling to voluntarily provide DNA for comparison testing; investigators may be unable to develop further evidence connecting the killer to the crimes. Every element must fall into place in order for forensic genealogy to help identify the Zodiac. The DNA database used in the Golden State Killer investigation contains the genetic information for approximately 960,000 individuals. The Ancestry.com and 23andMe databases contain approximately ten times as many genetic profiles but are not accessible to law enforcement investigations without a court order. Finding the Zodiac through forensic genealogy would be somewhat like searching for a needle in a haystack without knowing whether or not you are searching in the correct haystack.

The odds of finding a complete genetic profile of the Zodiac may be low but the possibility exists that new methods and technology could yield better results than previous efforts to obtain Zodiac DNA. While hope is certainly a reasonable position, even in spite of the long odds, the fact remains that those who have been waiting for decades to see the Zodiac identified may be disappointed if renewed testing fails to produce a substantial and useful DNA profile of the killer. We may be denied the solution to the Zodiac mystery despite our best hopes and the best efforts of law enforcement.

If the Zodiac is identified, most of the theorists who publicly accused suspects will be proven wrong, and all will be proven wrong if the Zodiac is identified as someone who has never been named as a suspect. A simple fact about any list of suspects puts the issue in proper perspective. A list of ten Zodiac suspects could include: Arthur Leigh Allen, Richard Marshall, “Andrew Todd Walker,” Bruce Davis, Richard Gaikowski, Earl Van Best, Jr., George Hodel, Edward Wayne Edwards, Larry Kane, and Mr. X. In any reasonable scenario, at least 9 of these men are not the Zodiac, meaning, at least 9 accusers are wrong about the identity of the Zodiac and have been accusing innocent men. Most likely, none of the 10 men are the Zodiac, and all 10 accusers are wrong. The overwhelming majority of those who publicly promote various suspects do so with virtually no credible evidence to justify their accusations, implied or direct, and the men they accuse will forever be defamed unless and until the Zodiac is identified.

Investigators had privately identified Gary Ridgway as a possible suspect in the Green River murders many years before DNA proved that he was the killer. Investigators identified Bryan Patrick Miller as a possible suspect in the “Canal killings” in Arizona before his DNA was matched to the killer’s DNA. The possibility exists that the DNA of a named suspect could match the Zodiac DNA taken from an envelope, but even this seemingly conclusive evidence could be insufficient to identify the suspect as the Zodiac unless that envelope contained a piece of the cab driver’s shirt and handwriting experts conclude that the suspect wrote the Zodiac letter. Most people would declare the case closed if the Zodiac DNA matched Arthur Leigh Allen’s DNA or that of any of the named suspects. Some theorists insisted that previous DNA comparisons which ruled out their suspects were somehow invalid because mysterious, unnamed accomplices had licked Zodiac envelopes for the suspects or even wrote the letters while another suspect committed the actual crimes. Talk of convenient accomplices would undoubtedly end if theorists learned that the DNA of their suspects matched the Zodiac DNA. Authorities would have difficulty obtaining evidence to further support the DNA match to an already-named suspect since most of the previously identified suspects have been cleared by other methods, including handwriting and fingerprints.

Dennis Rader was not known as a suspect before he was identified as the “BTK Strangler” responsible for murders in Kansas. He lived a seemingly normal life as a husband, father, local enforcement officer, and president of his church. Joseph James DeAngelo was not known as a suspect before he was identified as the “Golden State Killer” responsible for a dozen murders and many more sexual assaults in California. He lived a seemingly normal life as a father and worked for a local grocery distribution company. Many other murderers who avoided capture but were finally identified had never been named as suspects before, and the possibility exists that the Zodiac will be identified as someone never known as a suspect. A thorough investigation of the killer’s background will undoubtedly defy many common conceptions about the Zodiac and debunk many popular theories.

DNA evidence may be the last, best hope of solving the Zodiac mystery, and reports of new DNA testing inspire satisfying fantasies about seeing the image of the handcuffed killer on television screens. Identifying the elusive Zodiac killer would be a compelling end to this unsolved case and bring joy to many who have waited decades for justice, but the harsh reality may be frustrating and disappointing. The identity of the Zodiac may remain a mystery even as other notorious killers are identified and captured. As the 50th anniversary of the first known murders nears, the hunt for the Zodiac killer continues amid hopes that DNA will prove to be crime-fighting magic.


Writer/Zodiac researcher Michael Butterfield and author/host Alan R. Warren discuss the methods used to identify the Golden State Killer and how the same methods might identify the Zodiac in the latest episode of the House of Mystery series The Zodiac Files. CLICK HERE TO LISTEN NOW.