Who do you think you are? What DNA tests reveal—and what they don't

For more than 40 years, the Golden State Killer haunted California. A serial rapist and murderer active in the 1970s and '80s, he eluded detectives for decades. By 2018, hope of identifying him was fading, until a woman—curious about her ancestry—spat into a plastic tube and mailed it to a genealogy company.