In April 2018, California law enforcement investigators identified Joseph James DeAngelo, the Golden State Killer — responsible for at least thirteen murders and fifty rapes across California in the 1970s and 1980s — using genetic genealogy. DNA from crime scenes in Sacramento was uploaded to the open-source genealogy database GEDmatch, allowing investigators to identify distant relatives of the suspect and construct a family tree leading to DeAngelo in Citrus Heights, California. It was the most significant cold case breakthrough using forensic genealogy techniques.

The Golden State Killer case — especially through Michelle McNamara's posthumous true crime account I'll Be Gone in the Dark (2018) — became one of the most celebrated true crime literary works of the decade, raising questions about obsession, justice, and the ethics of genetic evidence gathering. The use of consumer genealogy databases to solve crimes also opened major literary and philosophical debates about genetic privacy, the rights of relatives whose DNA was used without consent, and the reach of the forensic state into private family history.