9 May 2018

How can researching your family tree catch a serial killer?

With the recent apprehension of the East Area Rapist/Original Night Stalker aka Golden State Killer through the use of DNA and family geneology matching, the issues of commercial DNA testing, online ancestry tracing and the ethics and implications of it all, have been much in the news. The ethical implications of making this kind of information publicly available and what it can be used for are a bit beyond this barely begun humble true crime blog. What's kind of fascinating, to me anyway, is the mechanics of how it all comes together. How can researching your family tree catch a serial killer?





Tracing your family tree using geneology websites like Ancestry.Com has become very popular in recent years, as has the use of commercial DNA testing sites like 23 and me, where people can collect their own DNA samples using saliva and send them to commercial labs to be tested to obtain their own DNA ancestry profile. People can then choose to post their family trees and DNA profiles online on the geneology sites, and if so whether they want to make the names public. Users can then search other profiles for DNA matches, which indicate shared ancestry

In the case of the Golden State killer, there were DNA samples collected from crime scenes and stored for many years; investigators knew they had a profile which had to match the killer. The profile did not match any criminals already in state and national DNA databases. But with the rise of commercial ancestry sites and DNA databases, investigators created a fake profile using the killer's DNA and searched  for matches. They found a partial match on an ancestry site, indicating shared ancestry. By searching the family tree of this match, they were able to identify a family member who matched the criminal's profile - age, sex, birthplace - and then, using more traditional policing surveillance methods, follow the suspected family member, obtaining their DNA profile from DNA discarded in a public place - possibly a used coffee cup or gum he threw away. When that DNA was a total match with the DNA obtained from long-ago crime scenes, police made their arrest.

A similar technique was used recently to identify a young woman found murdered in Ohio in 1981. Lacking an identity for 37 years, the young woman became known as the Buckskin Girl, after the distinctive handmade jacket she was wearing. In early 2018, a laboratory was able to achieve a DNA sequence for Buckskin Girl, using a vial of her blood stored since 1981. Volunteers at the DNA Doe Project then uploaded the DNA profile to geneological site GEDMatch, and searched through their existing databases for "cousin matches". They were able to identify a match, a woman who appeared to either share a single grandparent with Buckskin Girl or was first cousin to one of her parents.

Luckily, this woman had made her family tree publicly available, and it was through searching this family tree for cousins and their children that DNA Doe volunteers found a match - a woman born at the right time, Marcia King, listed as missing, presumed dead. This was Buckskin Girl, who now has her name back. Marcia King.

So uploading your family tree or DNA profile could identify a perpetrator or give one of the missing their name back. It's a fascinating area we'll be hearing a lot more about.

Sources 

DNA Doe Project https://www.facebook.com/DNADoeProject/posts/2048512292074212


False starts in search for Golden State Killer reveal the pitfalls of DNA testingnbsp;http://www.latimes.com/local/lanow/la-me-ln-golden-state-killer-dna-20180504-story.html

The Golden State Killer and DNA https://dna-explained.com/2018/04/30/the-golden-state-killer-and-dna/

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