I woke up yesterday morning to the news that GEDmatch, the open-source genetic genealogy website, was instrumental in identifying Joseph James DeAngelo as the man suspected to be the serial murderer and rapist known as the “Golden State Killer.” As a genealogist I have been a longtime GEDmatch user, and I am not at all sure how I feel about my DNA potentially being used in a criminal investigation on the other side of the Atlantic. While it is good that justice can be done and the affected families can finally have closure, many important ethical considerations have yet to be considered.

DNA testing is a very useful tool for the family historian. DNA on its own is not very informative, but when compared in large genetic genealogy databases and used in combination with online genealogical sources and social-media websites, it can be very powerful indeed. Adoptees, foundlings, and donor-conceived individuals now have the potential to discover their genetic or biological identity through DNA testing. If you match with a second cousin, you share the same great-grandparents. Using standard genealogical research methods, it is then just a question of tracing all the lines forward to the present day to identify suitable candidates who were in the right place at the right time. In some cases people are being matched with a parent or a sibling when they first test. Heart-warming DNA success stories are appearing on a daily basis, and genealogical brick walls have come tumbling down. While there are potential privacy implications in the exposure of long-held family secrets, it is generally recognized that the rights of the child trump the rights of the parents. Genetic genealogy is now correcting the ethical breaches of previous generations. An adoptee who is denied access to original birth records can now recover her genetic or biological identity or heritage. An individual born as the result of an anonymous sperm donor now has the possibility of identifying that donor and connecting with half-siblings.

It was perhaps inevitable that the same techniques genetic genealogists used to search for unknown parents would be deployed in criminal investigations. The precedent was set with the establishment of the DNA Doe Project, which had its first success earlier this month with the identification of the murder victim known as the “Buckskin Girl.” DNA was extracted from a blood sample taken during the autopsy. Full Genomes Corporation, a commercial genetic genealogy company, used next-generation sequencing to generate a DNA sequence from the degraded sample. A spoof GEDmatch kit was then created, and a match with a first cousin once removed provided the breakthrough. Full details of the methodology used in the Golden State Killer case have not yet been revealed, but it is likely that the techniques were similar.

While I applaud the innovative use of DNA technology in these cases, I have deep misgivings about the surreptitious use of GEDmatch by law enforcement and the lack of informed consent for the use not just of my data but the data of all the other one million GEDmatch users. All of us have the right to decide how our DNA and our own data is being used. The police force in a foreign country should not have the right to make that decision for me.

The combination of DNA and genealogy is a potentially a huge force for good in the world, but it must be used responsibly. In all cases where public databases like GEDmatch are used, the potential for good must be balanced against the potential for harm. In cases involving adoptee searches, missing persons, and unidentified bodies, the potential for good usually markedly outweighs the potential for harm.

But the situation is not so clear-cut when it comes to the search for suspects in rape and murder cases. The potential for harm is much higher under these circumstances, because misuse, misapplication, or misinterpretation of the data could lead to wrongful identification of suspects. The stakes are too high for the GEDmatch database to be used by the police without oversight by a court of law. 

However, we are not looking at a dystopian future. In the long run the public sharing of DNA data, when done responsibly, is likely to have huge benefits for society. If a criminal can be caught through a DNA match with a cousin, people will be less likely to commit a crime in the first place. With the move to whole-genome sequencing in forensic cases, it will be possible to make better use of genetic genealogy methods and databases to identify missing people, the remains of soldiers killed in action, and casualties from natural and manmade disasters. We will be able to give many more unidentified people the dignity of their identity in death. But we each control our own DNA and should all be able to decide what, if anything, we wish to share.