Well that's the thing there's a website you can upload DNA publicly and that's how they found the Golden State killer by that method. Here's the story on how they did it.
DNA Evidence from Crime Scenes: Investigators had DNA from crime scenes dating back decades, including from murders and rapes.
Genetic Genealogy Databases: In 2018, investigators used DNA evidence and compared it to publicly available DNA profiles on genealogy websites like GEDmatch.
Identifying Distant Relatives: This analysis led them to identify distant relatives of DeAngelo who had voluntarily uploaded their DNA to these sites.
Building a Family Tree: Investigators, working with genealogists, then painstakingly constructed a family tree, tracing lines from the distant relatives back through ancestors, according to The New York Times.
Narrowing Down Suspects: They narrowed the pool of potential suspects by considering factors like age, location, and other characteristics consistent with the Golden State Killer's profile.
Confirming the Suspect's Identity: Once DeAngelo was identified as the prime suspect, investigators collected his DNA from discarded items without his knowledge, such as a tissue and a swab from his car door.
Direct DNA Match: This DNA was then compared directly to the crime scene DNA, confirming a match and linking him to the crimes.
Arrest and Confession: DeAngelo was arrested in April 2018. He later pleaded guilty to 13 murders and admitted to numerous rapes and other crimes.
During an interrogation, he was recorded confessing to the crimes.
The case of the Golden State Killer is notable for being the first high-profile arrest made using this relatively new technique of investigative genetic genealogy. This approach has since been used to solve numerous other cold cases.
