The Golden State Killer—Joseph James DeAngelo—was caught after police matched him to a partial profile on GEDMatch. That’s a site that allows users to voluntarily upload their raw DNA data from sites like Ancestry.com and 23andMe.com. Essentially, some relative of DeAngelo’s was looking for further distant family connections and inadvertently outed him as one of the most vicious serial killers in California history. I am among the many who have had mixed feelings about this. I don’t have any mixed feelings about DeAngelo being put away for life. I enjoy thinking about that, and thinking about him as an old man suffering behind bars. I wish Michelle McNamara was here to see it, too. But I do get the privacy concerns. And I don’t know what to say about it. The part of me that’s been covering crime for years loves the idea that many more cold cases could be solved this way. My inner civil libertarian quails when thinking about how badly police could abuse this method of investigation. Until the public can be assured that police will use this kind of thing wisely, I won’t really know what to say about it. It’s a brave new world kind of thing, and there are always unknown challenges in that world.