A judge scheduled Karr's first appearance in Boulder County Court for Monday afternoon, a proceeding expected to last just moments.
Deputy Public Defender Seth Temin did not detail why he took the unusual step of asking the court to seal Karr's handwritten request to be represented by a publicly funded lawyer.
Some commentators have suggested that Karr's handwriting in a high school yearbook resembles the writing on a ransom note found in the Ramsey home a few hours before JonBenet's body was found on Dec. 26, 1996.
Without referring specifically to the speculation, Temin told the court in a filing Friday that he "is without sufficient knowledge about all the facts of the case to be able to evaluate the prejudice that may be associated with the release of any of the defendant's handwriting."
Karr, 41, was being held in an 8-by-10-foot cell, though he could have contact with one other inmate by way of a "sub-dayroom" adjoining his cell, sheriff's Cmdr. Bruce Haas said.
"His demeanor is calm. He's been resting," Haas said. "He's sleeping and hanging out — pretty uneventful."
The inmate, who dined on pate and wine during a flight from Thailand, faced a more prosaic menu behind bars: beef stew with buttered noodles for dinner, Spanish rice and chili dogs for lunch.
Six-year-old JonBenet, a photogenic contestant in child beauty pageants, was found strangled with a skull fracture in her family's mansion nearly a decade ago. Authorities once said parents John and Patsy Ramsey were under "an umbrella of suspicion," but prosecutors in this affluent college town at the foot of the Rocky Mountains have never charged anyone in the case that fascinated the nation.
Formal charges are still pending against Karr.
Boulder District Attorney Mary Lacy has refused to say what led to Karr's arrest, and persuaded a judge to seal the reasons she had Karr detained last week on charges of first-degree murder after deliberation, felony murder, first-degree kidnapping, second-degree kidnapping and sexual assault on a child.
"Despite what may have been disclosed to the public over the many years since the crime, most of the evidence in the affidavit has not been disclosed, nor has the media developed it independently," Assistant District Attorney William Nagel wrote in a court filing this week.
Karr's arrest in a low-rent tourist neighborhood of Bangkok followed four years of e-mail exchanges with a college professor who has made documentaries on the case, though Boulder authorities said in a legal filing that they learned his name only five days before the arrest.
Karr told authorities and reporters in Thailand he was present when JonBenet died, but no one has publicly placed him in Colorado at the time of the crime.
A brother, Nate Karr, on Friday issued the strongest alibi statement to date, saying he was certain the suspect spent Christmas 1996 with his family.
"I can say almost without question that from the time that John had children he has never missed a Christmas with his family, and that's any Christmas," Nate Karr told ABC's "Good Morning America." "If he was away from his family during Christmas, it would have been a family scandal."
The brother said he was uncertain where the family spent the holiday that year.
"To the best of our recollection, he was either with us in Atlanta or with (his ex-wife) Lara," Nate Karr said. "It's not as easy as you might think to remember 10 years ago."
Nate Karr told The Associated Press he was arranging to travel to Colorado to visit his brother in jail.