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My Fourth Cousins, The Golden State Killer, and the Fourth Amendment

The Golden State Killer, a serial murderer who operated in my home state, California, has been apprehended.  On Wednesday, when the news broke (ironically, on DNA Day), I was overjoyed.  Today, I have some very serious concerns.

From the plethora of news accounts I’ve read, it appears that the suspect in The Golden State Killer murders was apprehended using a public genetic genealogy database I’ve often used myself: Gedmatch.  The suspect in the case did not DNA test.  His identity was inferred from the DNA tests of others.  In other words, law enforcement used the same methodology I used to solve my own misattributed paternity case.

AncestryDNA and 23andMe have released press statements stating that they’ve not had any contact with law enforcement with respect to this case, that they protect the privacy of their members, and that they don’t share information with law enforcement unless, “compelled by a valid legal process.”  This is immensely important and reassuring.  I feel no need to pull my DNA nor the many DNA kits I manage from these sites.

That said, it does leave some DNA testing companies that offer third-party transfers as  potential pools for law enforcement to access for DNA fishing expeditions.  Specifically, Family Tree DNA and My Heritage.

This is troubling.

For those that haven’t read my blog in it’s entirety, I used my genetic fourth cousins to infer the identity of my biological father.  And I solved my own paternity case in five steps:

1. I DNA tested

2. I DNA matched people

3.  I created family trees for my DNA matches

3. I found the ancestors (great x3 grandparents) my DNA matches all had in common

4. I built those family trees forward in time to include virtually everyone genetically related to those in-common ancestors.

5. Eventually, I was left with a single pair of brothers that had all of the correct ancestors in their tree.  I didn’t know which one of the brothers was my biological father but I knew that their parents were my grandparents because all my fourth cousin DNA matches fit perfectly with *that* particular combination of ancestors.  And while I did test a first cousin once removed to these brothers and ultimately confirmed my hypothesis with my biological father having tested, the inference to him was already present from my DNA matches to cousins that he undoubtedly has never met and didn’t personally know.

Again, my DNA matches were made through ancestors we share that were born in the 1700’s.   How many people would this include?  Thousands.  Likely tens of thousands.

Where is the “probable cause?”

And that’s the problem with law enforcement tapping into these databases: you aren’t just consenting your DNA, you’re consenting bits of your DNA shared by all your genetic cousins for the last couple of hundred years (give or take).   This isn’t a Fourth Amendment issue if we’re talking about ordinary citizens creating family trees and connecting with cousins or closer family members in the privacy of their own homes for individual genealogical use.  After all, I don’t have the authority to arrest, try, and convict anyone of a crime.  And it’s not a crime to have a baby or a different father than you thought you had.  But when law enforcement can infer the identity of someone based on the DNA testing of others who haven’t consented to submit their DNA for the purpose of crime solving, I see an enormous civil rights violation.

Today, I have removed my kits from Gedmatch on behalf of my untested cousins and family members who have not consented to a law enforcement search.




Categories: Opinion

Laurie Pratt

Perpetually curious. I love history, genealogy, old movies, good books, all sorts of music, and adventures involving travel. In my spare time, I help admin a genetic genealogy Facebook page for CeCe Moore ("DNA Detectives") and coach people how to connect with their biological family using DNA.

9 replies

  1. Very well said. I, too, am removing my kits from Gedmatch. And while I am very happy that they caught this awful person, I am not comfortable with their use of a genealogical database to do it. Thank you for making the privacy and consent concerns very clear.

    Liked by 1 person

  2. I am not removing my DNA kits from GEDmatch. Why? Because California has a law on its books.It has been on the books since 2008. That law specifically details how law enforcement may use familial DNA. Part of that process includes probable cause and court orders. I strongly suggest that people not take news media hype as fact.

    Liked by 1 person

      1. I will give it a go. I believe it was in 1980 there was two rape kits done on one of the victims. That kit was in the freezer for 40 years. The DNA was run on that rape kit. In California in order to use familial DNA to identify someone. Several criteria had to be met. One is it is the only option left and another is the crime has to have been a violent crime. Then they go and present the case and a judge rules. Once law enforcement ran the rape kit. They then loaded it into available databases to run. After identifying possible suspects and in this case we don’t know if there was more than one. The police staked out the suspects house with a warrant and obtained another sample of DNA to compare to the one from the rape kit. The two samples were found to match.


      2. Laurie one more thing I would submit that he did submit his DNA when he raped women and left his DNA behind


    1. Law enforcement did not follow the California familial search protocol to find the GSK. There was no probable cause to search the 900,000 people in GEDmatch and they claim they didn’t need a court order to use GEDmatch. The criminals in the California offender database have far more privacy protections during formal familial searches than any of us did in this case.


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