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Is Tracing Criminals Through Their Family Trees A Violation of Privacy?

Photo of a DNA strand by Warren Umoh on Unsplash

Almost 30 years ago, a body found partially buried in Riverside County was unidentifiable due to the lack of resources at the time. But in 2021, the DA’s office used forensic genealogy to match the sample to the victim’s daughter. By December, the Cold Case team identified the victim as Patricia Cavallaro. Without the recent advancements in genealogy, this victim could never have been identified. ( 

Genealogy is the study of tracing family history through DNA. Companies like Ancestry and 23andMe use genealogy to give their users a family tree. These companies take a sample of your DNA and trace its heritage back as far as their database can. With the rise of these companies, law enforcement can now use these databases to identify victims, like Patricia Cavallaro, but they are more commonly used to identify criminals. It’s known as Investigative Genetic Genealogy, or IGG for short. They take a sample of any DNA left by the culprit and create a fake profile on these websites where they enter the DNA sample from the crime scene and see who the culprit’s relatives are. Then they learn as much as they can about the culprit’s family members hoping the information will lead to a possible suspect. For example, in 2018, IGG was successfully used to catch the Golden State Killer, who had murdered at least 13 people and raped 50 women throughout the 1970s and 80s. About 30 years after his last crime, investigators used GEDmatch, one of these heritage tracing companies, to find the family members of the Golden State Killer. Through the family tree, they found someone who matched the killer’s profile: Joseph James DeAngelo. The police then sampled his DNA and found that it matched the DNA from the crime scenes. ( Thirty years later, the rapist and murderer had been caught.  

The rise of IGG prompts the question: when is it appropriate to use? Because it’s a relatively new tool, there is no legislation (at least in California) restricting its use. Anyone who gives their sample to a commercial database is doing it to learn their heritage and their extended relatives, meaning they are not necessarily okay with their data being used in criminal investigations. Some people, therefore, view IGG as a direct violation of their privacy, and to some extent, that feeling is valid. So at what level is this privacy violation outweighed by the magnitude of the crime? Crimes have three categories: infractions, misdemeanors, and felonies. Infractions are the least severe type of crime. They result in tickets and fines. Next, misdemeanors result in a maximum of one year in jail and hefty fines. Lastly, felonies are the most severe types of crime, ranging from burglary to murder to rape. ( Should people’s family trees and DNA be used for all types of crimes, only for misdemeanors and felonies, or only for felonies? It is a more specific version of a broader question that has long since been debated in the U.S.: when does the government have the right to violate the people’s privacy? The debate over privacy has escalated in recent years with the rise of the Internet, for instance, manifesting itself in the Facebook-Cambridge Analytica scandal of 2018. People are increasingly concerned with their data being shared without their knowledge or consent, especially as more and more data is saved online. 

The debate over privacy and the use of people’s data in criminal investigations continues, but regardless, Investigative Genetic Genealogy is here to stay, for better or worse. How IGG will be used, remains to be seen, but it is imperative to remember the possible consequences of violating people’s privacy for the greater good.

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