Genetic genealogy caught the Golden State Killer – but is it ethical?

Looking for long-lost family on an ancestry website could turn you into a genetic informant. And while police in the US and Europe have caught killers using genealogy databases, this controversial practice has yet to be used in Britain. Steve Boggan investigates

Former police officer Joseph DeAngelo this week pleaded guilty to 13 murders and dozens of rapes (Reuters)

Two years ago, a wily detective on the cusp of retirement came up with a seemingly outrageous plan to catch a serial killer he had been hunting for 24 years – he would secretly plunder the fruits of personal DNA profiles shared online by amateur genealogists. In the absence of a hit on any police DNA databases, the investigator went about creating a false ID on an open source genealogy website called GEDmatch.com, and uploaded information from DNA found at the scene of a double murder. And then he waited.

Within 24 hours, the site had identified a list of people whose DNA shared some genetic markers with the killer’s, suggesting they must be related, no matter how remotely. Then followed four months of genealogy detective work as a team led by the detective, Paul Holes, a seasoned Californian investigator, created family trees dating back to 1840 and forward to the present day until one took them to the door of Joseph James DeAngelo, a former cop who, as the ‘Golden State Killer’, had murdered more than a dozen people in the 1970s and 1980s.

This week DeAngelo, 74, pleaded guilty to 13 murders and dozens of rapes. It was the conclusion of a brilliant piece of detective work, all followed to the letter of the law without breaching anybody’s legal rights to privacy.