DNA is what eventually “did in” the Golden State Killer.

KRON4 learned on Thursday how investigators, after decades of trying, arrested the 72-year-old man.

Joseph DeAngelo is accused of being the man who killed 12 people and raped more than 50 women in the 1970s and 1980s.

Many of the crimes happened in the Bay Area, terrorizing the community. 

He’s scheduled to be arraigned on Friday for two of the killings in Sacramento County.

Detectives used genealogy websites to track down the notorious killer.

KRON4 learned on Thursday the suspected Golden State Killer might have been caught thanks to DNA from one of his relatives put online.  

“You were not as smart as you thought you were,” a victim’s daughter Debbi Domingo said.

Domingo feels a sense of relief that police have caught the man accused of murdering her mother, Sheri, in their Santa Barbara home.

At Joseph DeAngelo’s house in Citrus Heights, FBI agents searched for clues connecting him to decades-old crimes brutally committed by the accused Golden State Killer.

DNA evidence is the strongest link between the man and dozens of decades-old rapes and murders.

“They did a surveillance, and they waited for him to discard something into the public domain,” Forensic DNA Consultant Dr. Ruth Ballard said. “Once they did that, they could take that item, whether it was a beer can or a cigarette or whatever, take it back to the lab and try and generate a profile from that.”

KRON4 has confirmed investigators used DNA from crime scenes and matched it to a relative of DeAngelo, who was registered on a genealogy website.

That is a place, for example, where people send in saliva swabs to learn about their ancestry.

And then, authorities narrowed it down to possible suspects, using that person’s family history.

“Just raised more questions for me as to how they did it, and what type of technology they used,” Forensic consultant and attorney Bicka Barlow said.

Barlow is a Bay Area-based forensic consultant and attorney.

She tells KRON4 this could be the first time law enforcement used commercial DNA databases to catch a killer.

“I think there are serious privacy and legal questions that surround this,” Barlow said.

It appears detectives matched the DNA from the crime scenes, to the internet, to an item DeAngelo possibly tossed in the trash.

For victims’ families, the hope is the DNA evidence will lead them to justice. 

“It is a lock,” Domingo said. “You can’t hide from DNA.”

The Sacramento District Attorney would not say which genealogy websites were involved. 

Both 23 and Me and Ancestry, which are Bay Area-based companies, denied to KRON4 having any connection to the case.

And they said they resist sharing customer information with law enforcement unless compelled to by a valid legal process.

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