How at-home DNA tests helped solve this 30-year-old murder

In 2019, American law enforcement agencies have identified over 70 suspects using a new technique called genetic genealogy, which California detectives leveraged in 2018 to identify the Golden State Killer. In the first of a two-part series, William Brangham shares the story of the first genetic genealogy case to go to trial — and how the science behind it solved a 32-year-old double murder.