Forensic Genealogy: What Your Second Cousin’s DNA May Say about You

“The DNA people said, ‘That was him. You got him.’ And the whole room just exploded. Some detectives were crying. Some detectives were sitting there with their mouths open, staring into space.”


Thanks to Colleen Fitzpatrick, a cold case that had baffled investigators for over two decades finally reached a breakthrough in 2014. She described the reaction in the Phoenix, AZ police department as a mixture of disbelief and elation. Fitzpatrick had just received the results of a DNA analysis obtained using a technique known as genetic genealogy, that narrowed the DNA profile down to just one individual out of over 2,000 suspects. Fitzpatrick, who has a PhD in nuclear physics, is a founder of Identifinders International, a company that provides genetic genealogy consulting services to solve forensic cases around the world.


Forensic Genealogy: What Your Second Cousin's DNA May Say About You

Written by: Ken Doyle, Promega



Although genetic genealogy itself isn’t new, its application to forensics is a relatively recent development. The technique relies on Y-DNA testing, which follows the male family line, making it popular among genealogists around the world. Forensic applications use the DNA profile derived from evidence at a crime scene to search multiple, public DNA profiles available in genealogy databases, with the goal of identifying possible family members related to a suspect. CeCe Moore, founder of The DNA Detectives Facebook group, explains how genetic genealogy works in this video.



Forensic genealogy relies heavily on access to public genealogy databases. Consumer DNA testing services such as and 23andMe are well-known among genealogy hobbyists, and they maintain their own collections of DNA sequence data. However, the site that gained fame in forensic genealogy doesn’t offer any DNA testing services at all. GEDmatch, unlike commercial DNA testing services, is a free, open-source database that relies on its users to voluntarily upload their DNA profile information obtained from commercial DNA testing.


At the time the site was launched, however, the founders of GEDmatch had no idea that their creation would be used to track down serial killers, rapists and others wanted by the law. Curtis Rogers, a retired businessman, and John Olson, a transportation engineer, developed GEDmatch as a side project during Rogers’ own quest to define his family tree. The site’s popularity grew rapidly, but Rogers was initially alarmed by the thought that law enforcement officials were searching a public database that held the DNA profiles of over a million Americans. Today, the GEDmatch web site contains a disclaimer about the potential use of the information by law enforcement agencies, mirroring legal language on consumer DNA testing web sites. In 2018, GEDmatch contained 1.5 to 2 million DNA profiles; it’s estimated that when that number approaches 3 million, it may be possible to determine the source of almost any DNA sample from a crime scene in the US. Not surprisingly, the ethical and privacy concerns raised by forensic genealogy continue to be a subject for intense debate.


The adoption of forensic genealogy in the US continues to proceed at a cautious pace. At present, less than a dozen states have passed legislation permitting the use of public genetic databases by law enforcement agencies. Maryland has already banned familial DNA searches, and it may become the first state to expressly prohibit forensic genealogical analysis with legislation currently pending.


International efforts to legislate forensic genealogy mirror the concerns that consumers face in the US. “There has been much criticism of the fact that existing users of genetic genealogy service providers have not explicitly given permission for their DNA to be used for law enforcement purposes,” says Dennis McNevin, PhD, Professor of Forensic Genetics at the University of Technology, Sydney, Australia. “If public trust in the process is eroded, then the whole idea of forensic genealogy could collapse as the public withdraws its support.”


If wider adoption of forensic genealogy methods is inevitable, forensic laboratories around the world will need to decide how best to incorporate the technology into their workflow. McNevin recommends that agencies start by working with their own intelligence analysts to determine how the capability can be implemented within the broader intelligence cycle. They should take into account the experience and qualifications of their investigators and prepare to tackle the complex questions that will arise from the use of forensic genealogical methods. “Finally, education of investigators and district attorneys’ offices is also crucial,” says McNevin.”


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The subject of genetic genealogy will be highlighted at two workshops during the 2019 International Symposium on Human Identification, to be held in Palm Springs, CA, September 23 – 26, 2019.


Jody Hynds will chair a workshop titled Family Ties: Using Genetic Genealogy to Solve Violent Crime. Hynds is a senior forensic scientist with the Orange County District Attorney’s Office, Santa Ana, California. This workshop includes three components: 1) an overview of consumer DNA testing and whole genome testing methods, instrumentation and bioinformatics; 2) demonstration of genealogical databases, family tree building and use of common websites; and 3) discussion of best practices developed by Californian prosecutors.


Attendees will develop a holistic understanding of investigative genetic genealogy and receive material that enables them to educate their respective communities on this revolutionary tool. The workshop will also enable attendees to develop a more comprehensive understanding of legal issues surrounding genetic genealogy and best practices to balance public safety with privacy concerns.

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Diahan Southard will chair a workshop titled Can You Solve Your Case Using Genetic Genealogy? Southard runs Your DNA Guide, a company providing education and assistance to anyone with DNA who wants to learn more about their family history. She also runs DNA Eyewitness, a company providing educational opportunities for law enforcement to learn how to apply DNA and family history in their investigations.


“The workshop will be a hands-on case study from start to finish,” says Southard, “so attendees will learn about what kinds of cases qualify for the use of genetic genealogy, as well as the step-by-step process involved.” Southard believes that the use of genetic genealogy in law enforcement is here to stay, and that it’s a powerful technology that has the potential to revolutionize how investigators approach casework.


Southard is actively working to educate law enforcement agencies on how they can apply genetic genealogy techniques, as well as the important protections that need to be in place regarding the use of DNA profiling data. She believes that the technology itself is not beyond the reach of most forensic laboratories. “The hard part,” she says, “is learning to use that profile, and the results of a genetic genealogy database, to get what you want.”

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