DNA Genealogy Names a Suspect in the 1973 Key Largo Killings of Two Sisters

The Florida Department of Law Enforcement and the Monroe County Sheriff's Office have identified a suspect in the 1973 killings of two New Jersey sisters whose bodies were found in a wooded area of Key Largo, closing an investigation that had gone unresolved for 53 years.

Investigators named David Allen Snyder as the suspect in the deaths of Marguerite Jenkins, known as Maggie, who was 18, and her 16-year-old sister Mary Jenkins. Snyder died in October 2008, which means he will never face prosecution. The identification came through forensic genetic genealogy, a technique that did not exist for most of the time the case remained open.

The announcement resolves one of the oldest unsolved homicide cases in the Florida Keys. The sisters traveled to Key West from New Jersey for a vacation in April 1973 and were last seen hitchhiking on Stock Island on May 2. A resident found their bodies the following day in a wooded area roughly 100 yards from US-1 near Mile Marker 99.5 in Key Largo. Both had been severely beaten and suffered apparent gunshot wounds.

How the case was solved

The original 1973 investigation produced no suspects. Forensic capability at the time was limited to blood typing, fingerprints, and physical trace evidence, and the case went cold.

The path to resolution began with evidence preservation. Investigators in 1973 collected and retained a blood stain found on one of the victims' clothing, and that evidence survived more than four decades of storage. Without that preservation, nothing that followed would have been possible.

In 2018, FDLE forensic scientists developed additional markers for a partial male DNA profile obtained from the stain and uploaded it to the Combined DNA Index System, the national DNA database. The profile reached the national level and returned no matches, meaning the contributor had never been entered into the system through an arrest or conviction.

That is where conventional DNA matching ends and where genetic genealogy begins. In 2023, FDLE conducted genealogy research, building a family tree alongside DNA analysis. That work narrowed the field to a family rather than an individual. Earlier this year, investigators collected a DNA sample from a Snyder relative and sent it to the FDLE crime laboratory, and the analysis confirmed Snyder as the source.

What forensic genetic genealogy is

The technique works differently from a database match. Rather than looking for an exact profile in a law enforcement database, investigators compare crime scene DNA against public genealogy databases populated by people who uploaded their own results from consumer ancestry testing.

Those comparisons identify relatives rather than the individual. A third or fourth cousin match gives genealogists a starting point, and from there they build family trees using public records, census data, obituaries, and vital records, working forward until they identify people who fit the geographic and temporal parameters of the case.

The final step requires confirmation. Genealogy narrows the field, and a direct DNA comparison confirms the identification. In this case, a sample from a Snyder relative provided that confirmation.

The method became widely known after its use in the 2018 identification of the Golden State Killer, and it has since resolved hundreds of cold cases nationally. It raises genuine privacy questions, because it identifies people through relatives who never consented to law enforcement use of their genetic information, and the major consumer testing companies have adopted varying policies on law enforcement access.

What investigators found about Snyder

Further investigation linked Snyder to residences in several locations in Key West between 1972 and 1974, placing him in the area at the time of the killings. That geographic and temporal connection supports the DNA identification with independent corroboration.

Snyder died in October 2008, roughly 35 years after the killings and a decade before FDLE developed the DNA profile that eventually led to him. He was never charged in the case during his lifetime and was never a suspect in the original investigation.

Because he is deceased, there will be no prosecution, no trial, and no formal adjudication of guilt. The identification represents an investigative conclusion by FDLE and the Monroe County Sheriff's Office rather than a court finding.

That distinction matters and is worth stating plainly. Deceased suspects cannot answer allegations, and cases resolved this way rest entirely on the strength of the forensic and investigative work rather than on a verdict.

The Jenkins sisters

Maggie and Mary Jenkins were teenagers from New Jersey on vacation in the Florida Keys in the spring of 1973. They were 18 and 16.

Hitchhiking, which is how they were last seen traveling on Stock Island, was a common practice among young travelers in the early 1970s in a way that is difficult to convey now. It was not regarded as unusual or particularly dangerous by many people at the time.

Their family waited 53 years for an answer. For relatives of homicide victims in long-unsolved cases, identification of a suspect provides something, though what it provides is limited when the suspect is dead. There is no trial to attend, no sentence to witness, and no accountability in the conventional sense.

The case has drawn attention from cold case researchers and genetic genealogy organizations, which have documented the investigative path that led to the identification.

Florida's cold case work

FDLE maintains forensic capability that local agencies across Florida draw on for cases they cannot resolve independently. The Monroe County Sheriff's Office, serving a county with a relatively small population spread across the Keys, is exactly the kind of agency that depends on state laboratory resources for work of this complexity.

The 2018 CODIS upload and the 2023 genealogy work represent a sustained multiyear commitment to a case with no living victims to advocate for it and no political pressure driving it. That kind of persistence is what distinguishes agencies that resolve cold cases from those that do not.

FDLE has been active on other fronts in recent weeks. The agency, working with Homeland Security Investigations, arrested a 76-year-old Summerland Key man on 11 counts of possession of child sexual abuse material. In August, FDLE arrested a Venice teenager over threats to conduct a mass shooting, and the agency joined Attorney General James Uthmeier in announcing the arrest of a Palm Beach County clerk of court on child sexual abuse charges.

What it means for Florida

For families of Florida homicide victims in unsolved cases, the Jenkins resolution demonstrates that evidence preserved decades ago can still produce answers. Agencies across the state hold physical evidence from cases going back to the 1960s and 1970s, and the genealogy technique continues to expand what can be done with it.

The practical constraint is resources. Genetic genealogy is labor-intensive, requiring skilled genealogists working for weeks or months per case, and laboratory capacity is finite. Agencies triage which cases receive that investment.

For the Florida Keys, a county with a small permanent population and a large transient visitor population, the case is a reminder of how difficult investigations were before modern forensics, when a victim and a suspect who were both temporary presences in a place could disappear from the record entirely.

The privacy debate the technique has created

Forensic genetic genealogy works because millions of people have uploaded their consumer DNA test results to public genealogy databases. Those uploads were made to find relatives, trace ancestry, and build family trees, not to assist criminal investigations.

The identification of a suspect through a third cousin means the cousin's genetic information was used to investigate a relative they may never have met. That person consented to genealogical research, not to law enforcement use, and there is no mechanism by which they could have anticipated the application.

The consumer testing industry has responded with varying policies. Some companies prohibit law enforcement access entirely, some permit it with a warrant, and some public upload databases allow users to opt in or out of law enforcement matching. That patchwork means the availability of the technique depends on which databases contain relevant matches and what those databases permit.

Courts have generally not restricted the technique, and no state has banned it outright, though several have adopted policies governing when investigators may use it. The typical restriction limits use to violent crimes and unidentified remains rather than property offenses.

The Jenkins case illustrates the argument in favor as clearly as any. A 53-year-old double homicide with no suspects, no database match, and no living witnesses is exactly the category of case that has no other path to resolution.

What preservation makes possible

The single most consequential decision in the Jenkins case was made in 1973 by investigators who collected and retained a blood stain from a victim's clothing. Nothing that followed would have been possible without it.

Evidence retention practices have varied enormously across agencies and across decades. Some jurisdictions destroyed physical evidence from closed or dormant cases to free storage space. Others retained everything. Florida law now requires preservation of physical evidence in certain categories of cases, but those requirements postdate the era in which many cold cases originated.

The Jenkins evidence survived more than four decades of storage in a climate that is hostile to biological material. Degradation is the limiting factor in old-case DNA work, and samples that were stored in unfavorable conditions frequently yield nothing usable.

The 2018 development of additional markers from a partial profile reflects laboratory technique that did not exist when the evidence was collected and barely existed when the case was reopened. Improvements in extracting usable profiles from degraded and limited samples continue, which means evidence that yields nothing today may yield an answer in a decade.

For agencies holding old evidence, that is the operative point. Preservation costs storage space. Destruction forecloses every future possibility.

What's next

With Snyder deceased, the criminal case is closed. FDLE and the Monroe County Sheriff's Office may continue investigating whether Snyder was connected to other unsolved cases from the period he lived in Key West between 1972 and 1974, which is standard practice when a suspect is identified in a cold case.

The broader trajectory is that forensic genetic genealogy continues to expand. As consumer genealogy databases grow and laboratory techniques improve for degraded and limited samples, cases previously considered unsolvable become workable.

For Florida agencies holding decades-old evidence, the Jenkins case is an argument for continued preservation. Evidence collected in 1973 by investigators who could not have imagined the technology that would eventually read it is what made this resolution possible.