The Golden State Killer, DNA, Ancestry, and Privacy: Three Reasons You Shouldn’t Worry

Have you read about how they caught the infamous Golden State Killer using DNA and a few popular websites that people use to trace their ancestry?  The genetic genealogy field has been buzzing with debates about privacy and ethics – but should you worry?  I have been hesitant to address this topic on my blog, primarily because there has already been a lot written about it on major publications.  I’ve received a lot of questions via e-mail, however, so I decided to weigh-in.

In this post, I’ll tell you three reasons why I don’t think you should worry too much about the way that DNA information was used by law enforcement and professional genealogists in order to determine the identity of a dangerous criminal, and why I still support DNA testing and the sharing nature of our online communities.

Before I go further into this topic, some background is appropriate.  Just to make sure that we are all on the same page working with the same facts.

  • No DNA testing company gave information to any law enforcement agency about any DNA testers or website users (i.e. Ancestry DNA, 23 and Me, My Heritage DNA, and Family Tree DNA did not share DNA data with law enforcement)
  • Law enforcement used common genetic genealogy strategies and DNA data obtained from a sample of DNA taken from a crime scene where the Golden State Killer had allegedly been in order to determine his identity
  • The DNA data from the Golden State Killer was uploaded to Gedmatch, a popular website used by professional and amateur genetic genealogists.  Law enforcement officials were able to see genetic matches to the killer, as well as some family tree information on some DNA matches.
  • The Golden State Killer, also known as his real name, Joseph James DeAngelo, was arrested after allegedly committing at least 13 murders, at least 50 rapes, and at least 100 burglaries.  The general consensus is that it’s a good thing that this guy is off the streets.

Note:  While I still recommend DNA testing and uploading to all of the major websites offering DNA testing and analysis, there are some important steps that you can take to protect your privacy, which I will discuss at the end of the post.

#1  Police don’t need your actual DNA or DNA file to track a criminal

As I mentioned in previously, the police were able to upload DNA information obtained from a DNA sample taken from a crime scene to the Gedmatch website.  The way the detectives, or a genealogist assisting the detectives, used the website is exactly how you and I would use it.  We’d upload our data, wait for it to process, and then perform a One-to-Many comparison to find all of our DNA matches on the site.

The results would look something like this:

what kind of information would be available to law enforcement on gedmatch

That’s it.  It’s just a list with some weird looking details on it.  From the image above, you can see that someone could tell where I did my DNA matches did their initial DNA test (“A” is for Ancestry in the kit number, for example).  They could learn whether my match is male or female, and see how much total DNA we share.  They could also see the length of the largest DNA segment that we share, as well as their name (or their designated alias), and the e-mail address that they used to set up their account.

Someone who is very skilled at genetic genealogy, the art of using DNA and genealogy to build a family tree, could use the above information to put together a basic family tree for me, especially if they have a subscription to Ancestry or another site for searching records.  And if we are honest, if they are law enforcement, they likely have access to some high-quality databases with information on living people, which is something most of us genealogists have trouble locating.

How would they build a tree?  Take my cousin Cathy as an example.  We share 134 cMs, which means that we are somewhere between second a third cousins, most likely.  With that knowledge, they research Cathy’s family tree, which she has on her Ancestry profile.  Second cousins share great-grandparents and third cousins share great-great grandparents.  They can then build a family tree using my cousin Allen’s information, and then see where the trees overlap – BINGO.  They’ll have found the people from whom I directly descend.  If they want to get really fancy, they could build a few more trees Jane and John’s trees (and their knowledge of how closely we are related).

If I had committed a crime, then they could make a list of all of the people who descend from the ancestor that they identified, which would be a pretty short list.  Then, they could eliminate my other family members based on geography, age, sex, and other factors.  They could then compare existing clues to narrow it down to one or two people – and then they’ve got me.

Phew – it’s a good thing I try to keep my nose out of trouble!

#2  Your DNA Isn’t Really Only Yours

Even if you decided that you don’t want your DNA to be in any database, it doesn’t matter.  Your identity, and the identity of any of your biological relatives can be found with varying degrees of effort by using the DNA of your distant relatives.


Because your DNA doesn’t only belong to you.  Your DNA is made of up tiny pieces of DNA called “DNA segments” that you inherited from thousands of ancestors.  All of those ancestors had other descendants and many of those descendants carry little pieces of DNA that they share in common with you.  To simplify this complicated topic, you can imagine that that you could basically assembly your entire genome (or at least most of it!) using DNA segments from all of your living close and distant relatives.

This means that even if you don’t do a DNA test, your sibling, parent, child, nephew, cousin, or aunt might decide to do so.  All of these relatives share a significant percentage of DNA with us, and their DNA information is enough to assist law enforcement in tracking down a criminal third cousin twice-removed or those volunteers searching for the identity of a Jane Doe in their process.  Even distant cousins can share large segments of DNA with us, and if you have enough distant cousins out there who have tested, a dedicated, knowledgeable professional could learn much more about us than we could imagine.

For me, the benefit of having my DNA in the database and being able to learn about my ancestors, build my family tree, and help my adopted cousins far exceeds my concern – especially considering that more than two dozen of my close and known extended family members have also done DNA tests.  If a member of my extended family decided to commit a terrible crime and law enforcement decided to use DNA, there is plenty of DNA information about my family floating around out there.  I won’t be able to stop anything by abandoning my hobby.

As I remember reading on a blog comment a few months ago: “The toothpaste is out of the tube”.  Might as well use it.

#3  Concern for the greater good should sometimes outweigh individual privacy concerns relating to DNA use

I’m sure we can all agree that it is a good thing that this heinous criminal was caught.  While I can’t speak for the family and close friends of the victims, I would be surprised to hear that any of them take issue with the methods used in the investigation.  People who uploaded their DNA to Gedmatch knew, or should know, that their information is going to be used by distant family members or even professional genealogists in order to build family trees.  Law enforcement basically built a family tree for the killer using the same information that you and I could obtain from uploading our DNA to the site.

This isn’t the first time that DNA has been used to track a dangerous criminal, and the attention that the Golden State Killer investigation attracted has encouraged the use of this strategy in other law enforcement agencies, meaning the potential to get more criminals are off the streets.  There are even volunteer groups who dedicate their time to help law enforcement identify the names of John and Jane Does, bringing closure to many families.

We exchange privacy for security all the time – DNA is no different

I believe that there are times when it is appropriate to make small privacy concessions in order to live in a safer society.  We do this all the time in other aspects of our lives.  For example, in order to have the freedom to drive a vehicle, we are required to register as a driver in a government database.  The idea is that it is safer to have licensed drivers instead of unlicensed drivers.  Some states even fingerprint people for a driver’s license, and all states collect personal information on their drivers.

Additional examples of privacy concessions in exchange for safety:

  • We allow ourselves to be intimately searched in order to board an airplane
  • When we go to a doctor, we tell them just about everything they ask about ourselves and our families in order to receive accurate and thorough medical care
  • If we want to keep our money in a bank, we have to provide a significant number of personal details to the bank, which they could share with the government in order to identify us as criminals should we exhibit suspicious banking behavior

In fact, we often exchange make major privacy concessions in exchange for things that don’t even make us safer.  Many of us appreciate free entertainment, services, and information available online –  so much so that we (happily?) let internet companies track our online activities to help other companies market to us more efficiently.

Basics on how to protect your DNA privacy in the age of the Golden State Killer

We leave traces of our lives all over the internet, but it is especially important to be aware of the type of details we reveal on the internet about our DNA.  This is precisely because our DNA doesn’t belong to just us – our entire family depends on us to use our DNA wisely (whether they know it or not!).  While I don’t think we should stress out about DNA privacy, or stop doing genetic genealogy altogether, I do feel like it is smart to take some precautions.

Here are some ideas on how to control the information that can be found about you on genealogy websites:

  • Create a designated e-mail address using an alias that you use to correspond with your DNA matches, and use this e-mail for every DNA website that you use
  • Make sure that you don’t post information about living family members on family tree websites
  • If you are especially concerned with privacy, make sure that all of your family tree information is set to private (not publicly viewable)
  • Research each site that you would like to use, especially if it requires you to upload your DNA.  If they don’t tell you what they plan to do with your DNA, consider asking them.  If they don’t provide a helpful answer, weigh the risk of using their service against the potential reward that you might gain from the information you could learn from their service.
  • Don’t post information like your Gedmatch kit # on public forums, Facebook groups, or other social media platforms.  If you would like to share this information, make sure to send it in a private message or an e-mail.
  • Remember that someone who is interested in learning about you (most like an adopted family member or someone trying to figure out how you might be related) will use Google to see what they can learn about you.  Most people are very innocent in their intentions and just want to determine your connection with them.  Keeping this in mind, Google yourself to see if you are comfortable with the information that is out there, and adjust your privacy settings as necessary.


I hope that this post helped shed some light on how DNA information was used in the case of the Golden State Killer, and helped you decide how comfortable to be with your DNA information being used in this manner.

I know that many of my readers will have strong views on this topic, and I would encourage you to share them in the discussion below.  I hope to keep the discussion friendly, however, since we will all learn better by keeping it civil.  Of course, if you have any questions, I would love to hear from you!

Thanks for stopping by today!

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The Golden State Killer, DNA, Ancestry, and Privacy_ Three Reasons You Shouldn't Worry
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The Golden State Killer, DNA, Ancestry, and Privacy_ Three Reasons You Shouldn't Worry
Have you read about how they caught the infamous Golden State Killer using DNA and a few popular websites that people use to trace their ancestry? In this post, I'll tell you three reasons why I don't think you should worry too much about the way that DNA information was used by law enforcement and professional genealogists in order to determine the identity of a dangerous criminal.
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