Joseph James DeAngelo, 72, was handcuffed in a wheelchair and five police officers surrounded him as he listened to the judge with his eyes barely open. He did not enter a plea and was denied bail.
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A court official read the details of the charges that DeAngelo is facing and a judge asked if he had a lawyer.
In a frail voice, DeAngelo responded, "I have a lawyer." An attorney from the public defender's office was with him in court.
DeAngelo appeared in a wheelchair and was wearing an orange jumpsuit.
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He's facing two counts of murder, but he is suspected of at least 10 more murders and upwards of 50 rapes from 1976 to 1986.
Sheriff Scott Jones said Friday that DeAngelo was in a psychiatric ward of the county jail and has said little. The sheriff also said there's been "quiet reflection" and mumbling to himself.
Jones said investigators are sifting through every item, receipt and piece of paper from DeAngelo's home. They're searching for any possible clues to tie him to more than 170 crimes authorities believe he may have committed.
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Police searched his Citrus Heights home on Thursday for possible murder weapons as well as trinkets the accused "Golden State Killer" might have stolen from his victims.
Investigators tracked down DeAngelo using a genealogy website that contained genetic information from a relative. It was revealed Friday that the Florida-based GEDmatch had no idea its database was tapped in pursuit of the killer.
GEDmatch co-founder Curtis Rogers said law enforcement's use of the site raised privacy concerns that were echoed by civil liberties groups.
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The free genealogy website, which pools DNA profiles that people upload and share publicly to find relatives, said it has always informed users its database can be used for other purposes. But Rogers said the company does not "hand out data."
"This was done without our knowledge, and it's been overwhelming," he told The Associated Press.
For the team of investigators tracking the attacker, GEDmatch was one of the best tools, lead investigator Paul Holes told the Mercury News in San Jose. Officials did not need a court order to access GEDMatch's large database of genetic blueprints, Holes said. Major commercial DNA companies say they do not give law enforcement access to their genetic data without a court order.
The Associated Press contributed to this report.