Los Angeles ? John Mark Karr, the suspect in the killing of 6-year-old JonBenet Ramsey, arrived late Sunday after a 15-hour flight from Thailand on which he sipped champagne, dined on fried king prawns and roast duck, and exchanged what he described as “small talk” with law enforcement escorts.

Agents wearing U.S. Customs shirts met him as he left the jet and accompanied him onto the jetway bridge to the terminal.

Karr voluntarily returned to the U.S. and was not handcuffed in his business class seat. He was expected to be detained by Los Angeles authorities pending a hearing on extradition to Boulder, Colo., where authorities have issued an arrest warrant for him.

He is expected to face charges in Boulder of first-degree murder, kidnapping and child sexual assault in connection with the young beauty queen’s 1996 killing.

Karr was to be processed by immigration officials in Los Angeles and arrested by local authorities on the Colorado warrant, said Carolyn French, spokeswoman for the Boulder County district attorney’s office.

A hearing was expected to take place in Los Angeles within a few days, French said, and if he agrees to waive extradition, Karr will then be taken to Boulder County.

“If he fights extradition that is a much more lengthy process,” French said.

The Los Angeles County district attorney’ office had not received word of an imminent hearing, spokeswoman Sandi Gibbons said.

“We’ve been presented with nothing,” Gibbons said. “If that is going to happen, no one has notified our office.”

Just before Karr boarded the flight, another bombshell emerged: Reports that he sought treatment at a Thai sex-change clinic.

Karr, dressed neatly in a red, short-sleeve, button-down shirt and black tie, was not handcuffed while being whisked through Don Muang International Airport in Bangkok. At a Thai Airways International departure gate, he talked amiably with fellow passengers. The 41-year-old teacher sat in a window seat next to Mark Spray, an investigator with the Boulder County District Attorney’s office.