January 28, 2022

Nabbing the “Golden State Killer”

Police used genealogy website

One of the worst cold case crime sprees in the US was settled in April when a 72-year-old former police officer, Joseph DeAngelo, was arrested. It is believed that DeAngelo had committed at least 12 murders, over 50 rapes, and over 100 burglaries in California between 1974 and 1986.

For decades, police were baffled. The “Golden State Killer”, as he was dubbed by the media, covered his tracks so well that they had no solid suspects although they did have DNA samples.

Then they resorted to a novel forensic technique – linking the DNA samples with names on a publicly accessible genealogy website. It did not take long to identify a number of distant relatives who shared the same great-great-great grandparents. From this information, investigators built up a large family tree and zeroed in on two suspects, one of whom was DeAngelo.

The news that the “Golden State Killer” had probably been caught was greeted with both relief and dismay. Relief that a vicious killer had finally been caught. But dismay that genetic information had been exploited by police. This was not a possibility that people envisaged when they submitted their DNA to the genealogy service.

An op-ed in Nature points out:

If police can use genetic databases to catch killers — even those who are distant relatives of individuals who have submitted their DNA — then perhaps more people will sign up to share their DNA. But they should be told that this is a possibility, and be given the choice to opt out. Meanwhile, more geneticists, ethicists and lawyers need to debate other potential ways in which genetic information is likely to be used, so that ethics leads the conversation, rather than playing catch-up.

In a similar vein, three bioethicists argued in The Hastings Center bioethics forum:

The methods used to catch the suspect were clever, scientifically sound, and done with laudable intent: to protect the public from a man thought to be responsible for a dozen murders and at least 45 rapes. But the process used to match the DNA sample of the unknown suspect with his relatives took unfair advantage of people who had submitted DNA samples for a very different purpose. In doing so, it called into question the privacy of DNA data being collected for a wide range of purposes.

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