Creepy or Cunning? How Cops Used DNA to Catch the Golden State Killer
Last month a 74 year-old US man, Joseph DeAngelo, better known as the Golden State Killer admitted to a string of violent crimes dating back to the 1970s, was spared the death penalty by finally admitting: “I did all that.” In coming weeks, it is expected he will be sentenced to life in prison in a second court hearing in Sacramento, California after a four-decades long manhunt for the Visalia Ransacker, the Diamond Knot Killer, the Original Night Stalker and the East Area Rapist. Shockingly, all just one man, a former police officer and one of America’s most prolific serial killers. His rap sheet of violent crimes spans two decades and beggar’s belief: nearly 60 home invasions, 50 rapes and 13 murders. At least 106 victims.
The Technology
Caught at last, but how?
The case of the Golden State serial killer, and how it was cracked in 2018 using DNA technology, coupled with mining publicly available genealogy data is a phenomenal example of cutting-edge forensic science.
While forensic DNA technology has been around since the early 90s, the Golden State serial killer evaded capture because he had no DNA profile stored on the NDIS (the National DNA Index System), an investigative database for known felons. DeAngelo simply flew under the radar and had never been swabbed for DNA. However, it was a crime journalist Michelle McNamara that first coined the name the Golden State Killer in 2013 in her blog the True Crime Diary, as online interest in solving California’s coldest serial killer case smouldered in crime forums run by citizen investigators.
The big break came in 2018 when detectives on the EAR Taskforce tapped into an emerging technique, known as genealogical searching for potential DNA relatedness. While partial matching and familial searching has been a recognised and regulated forensic technique for some time, this technique goes even further by bypassing criminal DNA databases altogether. Detectives mined a volunteer-run platform known as GEDMatch where consumers upload personal DNA results from direct-to-consumer genetic testing services such as 23andMe and Ancestry. The open-source database, created by the Mormon church, meant investigators did not require a court order to fish for potential relatives of the Golden State Killer.
The fishing expedition worked. Investigators identified distant members of DeAngelo's family, and they were able to zero in on the killer by triangulating his identity by using age, sex and where he lived to rule out suspects. On April 24, 2018 they had DeAngelo charged.
Ethical Implications
Is this the rise of the genetic surveillance state?
While the technique ultimately succeeded in helping investigators close the case, the high-profile case has sparked intense controversy over the ethical quagmire this poses, both on civil liberty and privacy.
Between the two leading direct-to-consumer DNA testing companies, there are now in excess of more than 10 million individual DNA samples.
While one family member may contribute and consent to their DNA information being included in a public genealogy database, others may not and therein lies the problem. Unlike the NDIS these sites are not regulated in any way. Critics of the technique say, in the wrong hands - and even the ‘right’ ones - there’s a worry that such powerful personal information could result in innocent people being subject to heightened scrutiny and surveillance.
Explore the science with STEM Reactor experiments
DNA Electrophoresis
A key technique used in research, industry and forensic sciences for understanding genetic variation.
Whose DNA Was Left Behind?
In this experiment, students compare dyes in simulated crime scene DNA with that of two suspects
DNA Paternity Testing
This experiment introduces students to the use of DNA fingerprinting in a simulated paternity determination. A child's DNA fingerprint is compared with his parents. The experiment does not contain human DNA.
Related Resources
Podcast: The Hunt for the Golden State Killer with Jason Henry
Image: Paul Holes, an investigator with the Contra Costa County district attorney’s office, was on the trail of the serial murderer and rapist known as the Golden State Killer for 24 years.
Podcast: The Genetic Detectives - A New Way to Solve a Murder, Part 1
Genealogy websites have led to major breakthroughs in decades-old cold cases. But the revelations may come at a price.
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Blog Sources:
https://www.wired.com/story/detectives-cracked-the-golden-state-killer-case-using-genetics/
https://www.sciencedirect.com/science/article/pii/S2589871X19301342
https://www.usatoday.com/story/news/politics/2020/01/22/golden-state-killer-case-progresses-pretrial-date-set/4543767002/
Ray A. Wickenheiser, Forensic genealogy, bioethics and the Golden State Killer case, Forensic Science International: Synergy, Volume 1, 2019, Pages 114-125, ISSN 2589-871X, https://doi.org/10.1016/j.fsisyn.2019.07.003.