The complaint filed by Mariposa County District Attorney Christine Johnson accuses Stayner of three counts of murder as well as special circumstances that could bring the death penalty.
Stayner confessed in late July to killing Carole Sund, her daughter Juli and their Argentine friend Silvina Pelosso, as well as Joie Ruth Armstrong, a naturalist at Yosemite National Park. But until today, he had been charged only with Armstrong's murder.
Specifically, the 4-page complaint charges Stayner, who worked at the Cedar Lodge motel where the three sightseers were last seen alive, with multiple murder, burglary, robbery, forcible oral copulation and attempted rape.
He's also charged with two weapons violations, said Betty Halencak, the court clerk in Mariposa.
An affidavit supporting the latest charges was filed, and sealed under the orders of Judge Richard L. McMechan.
For six months, Stayner eluded an intense search by an FBI task force formed to solve the slayings of the sightseers, who disappeared on February 15 during a trip to the park.
Only when the FBI arrested him at a nudist camp and questioned him in the July 21 death of Armstrong, in a remote corner of the park not far from the motel, did he confess to all four slayings.
Stayner, 38, told the FBI he sexually assaulted Silvina and Juli in their room at the Lodge before killing them. He also led agents to the still-bloody knives he said he used to decapitate the naturalist and slash the throat of Juli, a federal affidavit said.
The FBI quickly brought federal murder charges against Stayner in Armstrong's death, but despite his confessions and other supporting evidence, federal officials said they didn't want to charge Stayner in the other murders until ruling out the possibility that he had accomplices.
Federal charges were filed in Armstrong's murder because she was slain within a federal park. According to Stayner's confession, Carole and Silvina were killed at the motel, in Mariposa County, and he finally killed Juli hours later next to a reservoir in Tuolumne County.