Genetic Genealogy and the Golden State Killer

Police use DNA to exclude people. Genealogists cast a wide net to capture as many people as possible, all of someone's relatives. To find a killer, the genealogist simply uploads the killer's DNA and searches for partial matches. Those are relatives. Based on the percentage DNA in common, genealogists can then tell how closely related the killer is. From there, they can use obituaries, census records, and birth certificates to piece together a family tree and to find the killer himself.