SACRAMENTO (CBS13) — Catching the suspected East Area Rapist came down to diligent detective work through the use of DNA samples submitted to genealogical websites.

“From there, as I say, a lot of very dogged work by law enforcement to build the trees,” said Sacramento County District Attorney Anne Marie Schubert during a radio interview with KFBK.

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She says investigators were able to match the killer’s DNA through a family history website.

“It’s the greatest tool ever given to law enforcement to find the truth, whatever that is,” said Schubert speaking about the emergence of DNA technology.

Police collected decades-old DNA from one of the killer’s dozens of victims and submitted the sample to private genealogy websites.

The DNA results likely created a web of partial connections to people with a similar DNA profile as the killer.

Police dug through the details of matching relatives to see if they connected with the suspect. Their findings led them to a home in Citrus Heights and 72-year-old Joseph James DeAngelo.

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After surveying their target for several days, investigators collected DeAngelo’s DNA from something that he threw away. The connection could be made through blood, saliva, mucus, skin, or semen.

“Your DNA is going to be much more similar to someone with whom you’re biologically related, especially a close relative,” said forensic scientist Ruth Ballard.

She says with a matching sample, authorities can put DeAngelo at the scene of the crime decades ago.

“Knowing that that individual’s DNA will never be found in anyone else in the world,” said Ballard.

While Ballard says she doesn’t know exactly how police used the ancestry websites, she warns of potential legal issues as the case progresses.

“Every step along the way identifying him. if that was not a legal search, that then becomes a problem,” said Ballard.

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DeAngelo is due in court Friday afternoon for his arraignment.