Karr, 41, arrived in Los Angeles from Bangkok, where he had been arrested by Thai police in cooperation with US law enforcement officials.
Karr's arrest on Wednesday and his subsequent return to the United States have sparked a media frenzy in the nearly decade-old murder of the blonde beauty pageant princess that has appalled and fascinated many Americans.
"Mr. Karr will likely stay in Los Angeles two days, longer if he challenges extradition to Colorado to face charges in the murder case," said Los Angeles’ district attorney, Jane Robison.
The district attorney in Boulder, Colorado, where the 1996 crime was committed, said Karr will be advised at the Los Angeles hearing of the charges on the warrant and his rights regarding extradition to Colorado.
The Los Angeles Police Department has put Karr in a high-security cell at the Twin Towers Correctional Facility.
Karr faces charges of murder, kidnapping and child sexual assault if prosecutors find enough evidence.
Confession doubts
But Karr's alleged confession to Thai authorities in the crime has spawned speculation about whether he indeed is the killer of the little girl.
JonBenet’s beaten and strangled body was found in the basement wine cellar of her wealthy parents' Boulder home on December 26, 1996, the day after Christmas.
Thai police have said he had confessed to killing Ramsey unintentionally, telling them he was "in love" with JonBenet, who wore makeup and glamorous outfits and struck adult poses in her appearances at child beauty pageants.
But a former wife has said she was with him in the distant south-eastern state of Alabama the day JonBenet's body was found.
US officials tracked Karr to Bangkok after authorities studied four years of e-mails between him and University of Colorado journalism professor Michael Tracey, who has closely followed the Ramsey case.
According to excerpts of some of the e-mails published in the Rocky
Mountain News, the two discussed Karr's sexuality conflicts.
"I am trapped in a world that does not understand," Karr said in one exchange. "I can understand people like Michael Jackson and feel sympathy when he suffers as he has."
While his arrest has revived huge interest in the murder -- in which, at
one point, JonBenet's parents were investigated as possible suspects -- suspicions arose that Karr might not be the girl's killer.
Karr's ex-wife Lara Marie Knutson has said that on the day JonBenet's body was found, she was with Karr and their three sons in Alabama.
Her 11-year marriage to Karr ended in 2001, the year Karr was charged with possession of child pornography in Sonoma County, California, north of San Francisco.