This time she got into the building and through security screening before changing her mind.
"I want to leave," Superior Court spokesman Allan Parachini quoted her as saying. Parachini said Spears was driven away.
Upstairs, Commissioner Scott Gordon went ahead with a closed hearing.
"Notice was taken of Miss Spears' absence" during the hearing, the spokesman said.
Spears' lawyer argued that she be allowed to have visits and Federline was asked a few questions that required yes or no answers, Parachini said.
"I can't provide any more details except at the end of the day there was no change in the court order and Miss Spears has no visitation and no custody of the children," Parachini said.
The hearing was not scheduled and Spears was not ordered to be there, he said.
Both sides filed unspecified motions that reached the court Wednesday morning.
Each side asked to be heard without the other present but the commissioner held a joint session.
The next hearing is set for Feb. 4, at which time Spears attorneys will ask permission to withdraw from the case. A hearing on custody is set for Feb. 19.
The court spokesman said it was very unusual situation.
"Our primary concern is that two very young children are involved," he said. Spears, 26, and Federline, 29, are battling over sons Sean Preston, 2, and Jayden James, 1.
Earlier this month, Gordon suspended Spears' visitation rights and gave full legal and physical custody to Federline. Gordon kept that order in effect during an emergency hearing last week. That time Spears was driven into the civic center garage but decided to leave. She then was driven up to a street entrance, got out amid a swarm of paparazzi but only to try to move into the driver's seat. A companion ultimately drove her away.
The hearings followed a bizarre early January standoff at Spears' home when she refused to return the boys after a visit and was briefly hospitalized.
On Wednesday, Gordon called the Spears case at about 9:15 a.m., allowing Spears' attorney, Anne Kiley, to go out and try to find her client. Kiley returned about 20 minutes later and Gordon called the matter again.
"Is your client present?" he asked Kiley.
"No, she's not," the lawyer replied.
"Is she going to be present?" the commissioner asked.
"I don't know," Kiley said.
The commissioner then said there were motions filed by both sides but he didn't indicate what they were.
Federline and his attorney, Mark Vincent Kaplan, were in the courtroom. Federline was sworn in as a witness and Kaplan asked that the courtroom be cleared of spectators and the press.
Spears evaded swarms of paparazzi by arriving and leaving through a basement parking garage under the courthouse. She wore bright lipstick, sunglasses, gold platform shoes and a very short black cocktail dress with a ruffled hem.
Federline, clad in a tan suit and open-necked shirt and sporting a mohawk haircut, arrived a half hour before Spears.
