Golden State Killer Joseph DeAngelo: DNA From Ancestry Sites Helped Track Him Down

Joseph James DeAngelo, the alleged "Golden State Killer" (and a host of other nicknames based on his alleged crimes), was done in by DNA evidence provided to private ancestry DNA testing sites, the Sacramento Bee is reporting.

Ancestry DNA companies, such as 23andMe, MyHeritageDNA, and similar companies, all collect DNA samples from individuals who pay a fee. The companies then use that information, comparing users' samples to existing databases, to produce a general picture of where the user's ancestry came from.

It's a fun hobby that's been enjoyed by millions of users worldwide. And it's becoming a useful tool for law enforcement, it seems.

In the case of DeAngelo, authorities searched DNA databases from various ancestry DNA sites, using DNA collected decades ago from one of the Golden State Killer's crime scenes, and matching it up with California users who had provided DNA. Once authorities were able to hone in on the alleged killer's family tree, it was only a matter of time before they were led to DeAngelo.

After staking out his Sacramento home, authorities waited until DeAngelo was away, before obtaining an unidentified piece of trash that he had discarded. They tested it for his DNA, and sure enough, it was a match. That's when they knew they had their man.

DNA testing has been a tool to solve crimes for as long as the processes of extracting and examining DNA have been around. However, using DNA information from family members of suspects, called "Familial Line Testing," is comparatively new. California was the first state to legalize the practice, in 2008, followed by more than half a dozen states since then.

In fact, the first person believed to have been caught via Familial Line Testing was a rapist; Derek Sanders, who raped women and teenage girls in the Sacramento area between 1998 and 2003, was caught when DNA from his brother, also a convicted rapist, was matched to DNA evidence taken from Sanders' trash.

With the explosion of ancestry DNA testing, the pool of DNA samples from which to compare has expanded from just the prison population (and criminals who have already done their time) to huge swaths of the general public. This has been a boon to law enforcement, but it has also raised privacy concerns, according to the Atlanta Journal-Constitution.