Genealogy and the Golden State serial killer

Most people will have heard about the recent arrest of the so-called Golden State serial killer, responsible for 50 rapes and 12 murders committed across California in the 1970s and 80s. He was identified by matching his DNA with samples taken from the crime scene, as in many other cases. What really caught my attention was the role genealogy played.

Police uploaded the crime-scene DNA to GEDmatch, the open-source genealogical DNA website, and compared it with the three-quarters of a million samples already on the site. This identified what looked like some third- and fourth-cousin matches. They then followed the accompanying family history information on the site and used it to build out more than twenty-five multigenerational family trees, using the research techniques any genealogist would.

Unlike a genealogist, though, they were aiming to winnow the family trees down to men living in the right areas at the times the crimes were committed. This is what ultimately led them to Joseph James DeAngelo in Sacramento. A covertly-taken sample of his DNA matched that from the crime-scene.

Joseph James DeAngelo

By all accounts the crimes were horrific, and if DeAngelo committed them, it’s wonderful he has been caught, and equally wonderful that genealogy helped do it.

But one of the problems that bedevils familial DNA matching is the number of false positives. My own test results are up on GEDmatch and I regularly get approached by people who see a distant match but have absolutely no discernible connection to my family. And that happened in this case. Before finding DeAngelo, at least one and almost certainly more than one suspect was compulsorily tested and ruled out. In the United Kingdom, a 2014 study found that just 17 percent of familial DNA searches resulted in the identification of a relative of the true offender. Which means four innocent suspects for every guilty one.

And that’s not the most troubling part of the story. By putting my sample into a publicly available database like GEDmatch, I have made the DNA of hundreds of related people also available for searching. I consented, they didn’t. The same is true for the tens of millions connected to the other GEDmatch profiles.

Finding a serial killer is a wonderful, exceptional case. But what about a health insurance company using these records to weed out the potentially ill across extended families? What about being flagged as a suspect for a crime you have no connection with, because someone very distantly related has uploaded their DNA? What about employers screening for the “right” kind of family background?

As evidence in the most serious crimes, familial DNA should certainly continue to be available to police, with safeguards. But the kind of no-rules access to DNA samples provided by GEDmatch looks increasingly unwise.

I don’t know whether to leave my sample there or not. I suspect that cat is long out of the bag.


10 thoughts on “Genealogy and the Golden State serial killer”

  1. In a world where keeping strange men’s opinions on birth control out of my pants is a real issue, this is a non-brainer. Our DNA, like our fingerprints, are left wherever we have been. Increasingly small amounts are required to make or disprove a match. As an attorney I can tell assure you that in the USA you have no right to privacy in the DNA of your distant cousin any more than you have a right to privacy in his/her trash left at the curb. Life is not filled with perfect choices. Choosing between law abiding folks looking to complete genealogies/find birth family versus rape/murder suspects is not hard. I haven’t spoken to many who would deny the upside of consensual, if unknowing, DNA testing used this way. There is a line drawn by what DNA testing can be court ordered (compelled) versus what you voluntarily make public. In a country where more than 9,000 murders and tens of thousands of rapes go unsolved every year, I am convinced that any police department not using Gedmatch and genealogists need to get with that program. Where do I volunteer to help?

    1. Not sure how one privacy issue (birth control) has to do with another (use of DNA without consent) but I bet you feel better about getting in your political position. Go you.

  2. There would have been no hue and cry if the man were identified using Gedmatch simply because he had an inheritance or his lost family was looking for him. It’d be a feel good success story.

    I see the purpose of Gedmatch is to help people find other people. People who also put their data online and who understand that along that path, yet other people (who didn’t put data on gedmatch) would be “uncovered” as well. (Isn’t that what genealogy is all about?)

    The issue folks are “finding” an “ethical” issue is which searches are “good” and which are “bad”. Cost me an inheritance because Gedmatch found a better heir and I’ll have one opinion about good and bad, find out I’m that better heir and I’ll have another.

    A search is a search is a search.

    The problem with worrying about the privacy of the thousands of people genetically connected to me is that it , if given equivalency to my own privacy, makes genealogy impossible. Likely even old fashioned paper genealogy (just consider how many people bristle at finding out that birth, death and marriage records are available to buy or for free, directories exist that say where they lived etc.) Frankly, my DNA is mine, no one else has my 23 chromosomes and if I want to share that, it’s my call. The fact that unknown relations of whatever stripe may share portions of their own unique DNA with me doesn’t give either of us claim over how each uses their own unique DNA. Recognizing that while I may shed DNA everywhere I go lets people with means get and take their own samples outside my control is a different and distinct issue from me taking my own sample and putting it on a web site so people can find me.

    Caveat – However, if one were talking about whole genome sequencing analysis (which does include genetic markers related to medical and likely other biological issues), then I would give your concerns more weight. And in 10 years, the price may be such that people can have that done like they do testing today and that will require a big discussion with testing companies and the FDA (in USA) and others about what really is in that test result and what portion is appropriate for public disclosure.

    But the 23andmme or DNA testing isn’t whole genome sequencing and in it’s current form on Gedmatch is only efficient in tracking down people who may or may not be related to you. Play or down’t play as you see fit but I’m not seeing any ethical or moral issues in police use. (Hey cops, can’t use the data I put on Facebook because I didn’t put it there for you to chase me down….)

    Last, I do hope they gave those families their family trees – 25 trees done in depth is too good to not give to those folks.

  3. GEDmatch is actually run by super-intelligent lizards in human guise who control our reality from the Moon.

  4. As a person who lived in California, USA during his reign of terror and through the ever present fear this sadistic man left by his heinous acts, I must say that I’m willing to give up some personal privacy for the greater good of society and for its safety. This article only touches on his crime wave since now it is believed that he may also be responsible for 100 burglaries throughout the state as well. Having previously worked in health care, I understand the concerns of DNA being used in unethical ways, and yet, I keep going back to the notion that I hope the justice system would step up should DNA be used in ways that would blatantly discriminate others. Such laws are already in place, and if need be, others could be enacted. P.S. This crazy killer lived behind my mother’s house on the adjacent street.

  5. This article highlights what John considers to be the problems regarding the use of DNA to apprehend criminals. I believe that the following points are relevant when considering the feasibility of using DNA for this purpose.
    John mentions false matches but these d do not occur in the case of close matches/immediate relatives and therefore this fact should re-reassure people that they will not be arrested by mistake. However it may happen that at times a number of people will be tested in order to eliminate or narrow down potential criminals. Do they have to be arrested in order to obtain same?
    At the moment in this country where the Kerry babies were located a number of people have had their DNA tested both in order to eliminate them from the search for the father and in order to identify same. I assume that these people recognized the importance of this action and to date no publicity has been given by the police nor the media to those tested. This procedure must have been undertaken with discretion and confidentiality and I for one feel that it is for the common good that this be done as it could expedite the arrest of a culprit and could possibly save lives.
    He quotes the UK survey where only approximately 1 in 5 tested were guilty of a crime but the fact that they were ruled out demonstrates the authenticity of the testing process. If my relative had murdered someone and I ended up being tested then I feel that it is my duty to support such an action by the policein order to bring a criminal to justice, whoever he may be.
    The facility exists to have your DNA tested with a view to looking for matches without revealing your identity. It is not essential to upload to Gedmatch and if, having done so, you do not wish to reply to a request for contact then you are under no obligation to do so.
    If the full genome test becomes available/cheaper it will still be possible to get tested without undergoing the health test and it is to be assumed that legislation will cover any potential abuse of same. I have undertaken the 23&me test but nobody else has the right to read my results nor identify me.
    My experience of Gedmatch leads me to believe that it is an extra tool for the genealogist to be used alongside their other tools. I have been involved in finding the biological relatives of 3 adoptees and I could not have done so without Gedmatch. I have found all those that I contacted to have acted with respect and sensitivity towards me and while some people didn’t want further contact there was no issue when they made that choice. There is nothing to stop a person from removing their details should they feel so inclined.
    I feel that Facebook is a much more intrusive tool and yet it has survived. Like anything new DNA causes people to feel unsure and a bit frightened of it but I think that that reaction comes from a lack of in-depth knowledge of the package. The advantages vastly outweigh the disadvantages and I have found alot of relatives that I might never have come across were it not for Gedmatch.
    Jo Treston

  6. I have thought about taking a DNA test, but have not done so for two reasons.
    Firstly, over the last century, my family has spread around the world from Ireland to England, Australia, New Zealand and the USA. If I have something medically nasty in my DNA that I share with a distant cousin that they don’t know about, it is possible they might lose their medical insurance cover through no fault of their own.
    Secondly, I don’t know what use would be made of my DNA sample after my death. What guarantees are there that it won’t then be used as in my first objection?

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