Solving Violent Crime with Forensic Investigative Genetic Genealogy: An In-Depth Look

By: National District Attorney’s Association Forensic Science Working Group

About our Forensic Investigative Genetic Genealogy (FIGG) Blog Series: We’re taking a deep dive into Forensic Investigative Genetic Genealogy (FIGG). This three-part exploration begins with an introduction to this cutting-edge technique followed by a look into the ethical and privacy implications associated with FIGG. This final article below offers a detailed examination of FIGG’s various facets, providing a thorough understanding of this evolving technique.

June 29, 2020 was, as then Sacramento County District Attorney Anne Marie Schubert declared “a good day for the People.” On that day, Joseph James DeAngelo, dubbed the Golden State Killer, pleaded guilty to 13 murder counts, 13 kidnap for robbery counts related to rapes he committed, and also admitted to 62 uncharged counts of rape and other crimes. On August 21, 2020, DeAngelo was sentenced to 11 consecutive life sentences without the possibility of parole, an additional life term, plus eight years.

Arrested in April 2018, this notorious, sadistic rapist and murderer who terrorized communities throughout California in the 1970’s and 1980’s eluded capture until the unleashing of a revolutionary investigative tool known as Forensic Investigative Genetic Genealogy (FIGG).[1]

Since DeAngelo’s arrest in 2018, law enforcement agencies throughout this country enthusiastically harnessed the power of this technology to solve and close over 500 murder and rape cases,[2] bringing a ray of hope to a dark journey faced by victims and victims’ families. The advent of this new technology has greatly enhanced law enforcement’s ability to identify perpetrators of unspeakable crimes. Furthermore, even though many of the cases are decades old, many of these murderers and rapists are still alive and living among us in our towns and communities. Using FIGG to identify these criminals and hold them accountable for their crimes has exponentially improved the safety and security of our neighborhoods.

FIGG: An Introduction

In the past two decades, law enforcement has capitalized on the power of forensic DNA as a potent crime fighting tool. DNA can not only be used to identify suspects and convict guilty perpetrators, but also to exonerate the innocent.

Traditional and well-established forensic DNA testing methods using autosomal Short Tandem Repeat (STR) and Y-STR technologies[3] have transformed the criminal justice system. Uploading and searching DNA STR profiles in CODIS,[4] the national DNA database maintained by the Federal Bureau of Investigation (FBI), provides matches between forensic unknown samples and offender samples, thus placing a suspect or a person of interest at the scene of a crime, or linking crime scenes together. By sharing DNA information through this CODIS nationwide network, law enforcement’s robust efforts utilizing DNA to solve crimes have seen great successes. However, in spite of these advances, investigators’ efforts to solve cases are stymied when a CODIS search fails to provide a match because the suspect’s DNA is not uploaded into the CODIS database. States permitting law enforcement to utilize CODIS Familial Searches[5] may also see success, but only a handful of states permit Familial Searches. Thanks to the development of the revolutionary FIGG technique, law enforcement can now re-open and solve those cold cases once considered unsolvable.

FIGG raises forensic DNA testing, heralded as the greatest crime-fighting tool of the 20th Century, to new heights. Law enforcement, no longer limited to just CODIS database searches, can seize the opportunity to solve unspeakable crimes such as rapes and murders by identifying the perpetrators of these heinous crimes and bring them to justice. These perpetrators must now face their day of reckoning and account for the days and years they stole from their victims.

Although law enforcement has only been using FIGG to solve violent crimes for about five years, the nuts and bolts of the technique have been known for years by genealogy enthusiasts. It is essentially the same technique used by millions of adoptees and donor-conceived children, who like genealogy enthusiasts all over the world, utilize family matching databases to build family trees and discover new relatives.

FIGG: How it Works

Compared to traditional forensic DNA analysis, FIGG uses more genetic information from a larger portion of an individual’s DNA. Traditional forensic DNA analysis utilizes approximately 20 short segments of DNA known as STRs to generate an identifying profile. FIGG however, relies on an individual’s single nucleotide polymorphisms (SNPs)[6] profile. SNPs are spread throughout an individual’s entire genome and account for genetic differences among individuals. Early FIGG SNP analysis utilized SNP microarray chips of close to one million SNPs. Today, a FIGG investigation can rely on fewer SNPs (e.g., 10,000), targeting only those “identity SNPs” which are useful for kinship analysis.

Generally, law enforcement will utilize a Direct-to-Consumer (DTC) genetic testing company,[7] a private company offering forensic genealogy services, or the openly accessible genealogy database GEDmatch. GEDmatch is a genealogical database that combines DNA profiles from all DTC genetic testing companies in a central location, should a user choose to upload their SNP data file. This allows users to upload and share their SNP profiles, with an option to share this information with law enforcement. GEDmatch also provides tools to assist users in identifying potential genetic relatives in the GEDmatch database.

Law enforcement begins a genetic genealogy investigation by sending the probative crime scene evidence to a laboratory to generate a DNA SNP profile. Once developed, this DNA SNP profile is uploaded to a commercial genetic genealogy database, such as GEDmatch.[8] The SNP profile is compared to other SNP profiles in the database and a list is generated that identifies relatives of the contributor to the crime scene DNA profile. The database compares the profiles, identifies shared DNA segments, adds these shared segments together, and calculates the total amount of shared DNA. The total amount of shared DNA is expressed as centimorgans (cM), a measure of genetic distance. The sum of an individual’s shared segments across all chromosomes can be used to determine the genetic relatedness between individuals.[9] The more DNA shared between the DNA abandoned at the crime scene and individuals in the database, the closer the relationship between the donor of the crime scene DNA and that individual.

After a list is obtained, detectives and genetic genealogists investigate the identified genetic relatives and utilize public records such as U.S. Census records, birth certificates, death certificates, gravesite locaters, and newspaper clippings to build family trees to determine particular relationships. They focus on those who share DNA in common not only with the crime scene profile but also with any identified relatives, a process known as triangulation. The investigators build family trees to connect familial relationships, narrowing down the list of all relatives in order to hone in on a potential suspect. Case-specific facts such as geographical location and approximate age of the perpetrator are also used to further refine the search for a potential suspect.

The identification of a potential suspect serves only as an investigative lead for law enforcement. It is important to note that no arrests are made solely based on an investigative lead provided by FIGG. A new DNA sample must be lawfully obtained from the suspect, and sent to the forensic laboratory for traditional STR DNA testing, with the resulting STR DNA profile then being compared to the crime scene STR profile developed at the inception of the case. Only when this process is completed, and the crime scene DNA matches the DNA sample obtained from the potential suspect, is an arrest made.

FIGG: Privacy Interests

This groundbreaking investigative tool, although lauded around the globe for revolutionizing the crime-solving capability of law enforcement, has raised concerns by some about individual and family privacy.

In any discussion related to privacy, it is critical to recognize law enforcement’s singular purpose for utilizing this technique. Law enforcement is focused on one question: who is the source of the abandoned DNA at the crime scene? Since traditional methods of identifying the suspect such as uploading the DNA to CODIS or conducting a Familial Search may have been unsuccessful, law enforcement utilizes FIGG to determine who may be related to the DNA abandoned at the crime scene in order to develop investigative leads.

Law enforcement has no interest in health information, insurance coverage, or medical research. Law enforcement is like any other consumer using a genetic genealogy service to learn about genetic relatedness. Law enforcement, like the consumer utilizing these services, receives only a list of potential relatives of the unidentified suspect whose DNA was abandoned at the crime scene. These individuals have chosen to share their DNA profile in the database and opted to allow law enforcement to utilize this information. It bears repeating that the DNA profiles of those relatives are not given to law enforcement, but rather law enforcement has access only to the same information available to the public, that being their name and possible degree of kinship with the unknown DNA profile. Investigators then use the list of relatives as an investigative lead in an effort to determine the identity of the individual responsible for the crime.

FIGG: Memorandum of Understanding

As prosecutors, it is incumbent upon us to appropriately balance public safety and law enforcement’s use of FIGG against the privacy interests of individuals.

Several District Attorney offices in California have developed Memorandums of Understanding (MOUs) between law enforcement and prosecutors.[10] Details germane to particular agencies and departments may dictate how FIGG will be utilized, but the overarching goal of any MOU should be to protect the privacy interests of those individuals identified during the genealogy comparison. Other key elements worthy of consideration in an MOU include limited use/purpose, privacy protection for named putative relatives, and post-investigation strategies regarding maintaining FIGG information. An MOU developed to address these concerns will result in law enforcement’s success in balancing public safety with privacy when utilizing this innovative new tool to solve violent crime.

FIGG: Legislation

In 2021, Maryland passed legislation regulating and limiting the use of FIGG. The state of Montana soon followed with similar legislation. The legislation in both states requires judicial authorization for the use of FIGG in criminal investigations. In 2023, the Utah legislature gave final approval to a bill which sets guardrails on the use of FIGG.

FIGG: Conclusion

The pioneering use of FIGG has revolutionized law enforcement’s ability to solve violent crime. By fostering a culture of responsible use through a MOU or other best practices model, prosecutors can promote the wider application of FIGG to solve violent crimes while respecting individual and genetic privacy. NDAA strongly supports and applauds those law enforcement agencies which, since the 2018 arrest of the Golden State Killer, have responsibly utilized this groundbreaking technology to solve decades-old crimes, lift the clouds of suspicion from individuals under investigation, and most importantly, provide answers, relief, and ultimately justice to those who have suffered the most . . . the victims and families of victims of these devastating crimes.

[1] This investigative tool originally called “investigative Genetic Genealogy” is today more commonly referred to as “Forensic Investigative Genetic Genealogy (FIGG).” The Department of Justice identifies the technique as “Forensic Genetic Genealogical DNA Analysis and Searching (FGGS)”.

[2] See Forensic Genetic Genealogy Project v. 2022, Mendeley Data. Contributor: Tracey Dowdeswell, Douglas College Faculty of Humanities and Social Sciences.

[3] Forensic DNA typing utilizes accordion like stretches of DNA containing tandemly repeating units. The number of repeating units can vary between individuals thus making this typing method a powerful tool in human identification. (Butler, John M. Advanced Topics in Forensic DNA Typing: Methodology. San Diego: Elsevier Academic Press. pp. 99–100, 2011.)

[4] The Combined DNA Index System (CODIS) consists of three databases of information: Local DNA Index System (LDIS); State DNA Index System (SDIS) [which allows laboratories within a state to share and compare uploaded DNA profiles within the state]; and National DNA Index System (NDIS) [which allows states to share and compare DNA profiles with each other nationwide].

[5] A Familial Search is a deliberate search of a DNA database using specialized software to detect and statistically rank a list of potential candidates in the DNA Database who may be close biological relatives (e.g., parent, child, sibling) to the unknown individual contributing the DNA [https://ncjrs.govnij.grants].

[6] A single nucleotide polymorphism is a variation at a single nucleotide in a DNA sequence among individuals. (Butler, John M. Fundamentals of Forensic DNA Typing. San Diego: Elsevier Academic Press. p. 463, 2009)

[7] E.g., FamilyTreeDNA

[8] Law enforcement is permitted access to SNP profiles from those consumers who have “opted-in” to share information with law enforcement.

[9] See Gretak, (2019) Genetic Genealogy for Cold Case and Active Investigations. Forensic Science International 299, 103–113.

[10] The California District Attorneys’ offices have modeled their best practice MOUs after the California Department of Justice Familial Search policy adopted by then-Attorney General Jerry Brown.

Interested in other parts of this three-part series?
Part 1 provides an introduction to this cutting-edge technique.
Part 2 looks into the ethical and privacy implications associated with FIGG.



National District Attorneys Association

The National District Attorneys Association (NDAA) is the oldest and largest national organization representing state and local prosecutors in the country.