Ousted U.S. Park Police chief Teresa C. Chambers took the witness stand yesterday in her bid to reclaim the job and testified that she would not knowingly defy a superior.

During about two hours of questioning by her attorney, Mick Harrison, Chambers sought to portray herself as a forceful advocate for the needs of the Park Police, but not so driven that she would disobey direct orders.

"There was much more that needed to be done, and we were obligated to do it," she said.

Chambers told the court that she did not want to have to stand amid the ruins of the Washington Monument or the Statue of Liberty and have to explain why she had not done more to safeguard such national treasures.

"I believed I was doing what needed to be done," she said.

Chambers, who was chief for 22 months before being placed on administrative leave in December and formally fired in July, contends her dismissal was unjustified and retaliatory and is asking a federal board to reinstate her. But her bosses at the National Park Service, which oversees the Park Police, have said that she repeatedly flouted the agency's rules and protocols and that her dismissal should stand.

This week in Alexandria, an administrative law judge for the U.S. Merit Systems Protection Board has been hearing testimony in the case.

Chambers has turned the fight for her job into a crusade, using a Web site, petition campaign and media savvy.

In fact, it was her encounters with the media that led to her firing. In interviews with The Washington Post and other news organizations late last year, Chambers said the Park Police did not have enough money or personnel to meet the many additional responsibilities thrust upon the 620-officer force after the Sept. 11, 2001, terrorist attacks.

Her supervisors then accused of her of disclosing sensitive security and budget information and of lobbying Congress, directly and through the press.

Park Police are responsible for patrolling the Mall, other national parks in the area and the region's parkways, and for securing some national sites in New York and San Francisco. But security demands in the wake of the terrorist strikes have forced the agency to focus on guarding major landmarks and to limit its criminal and traffic enforcement work.

While the interviews with reporters late last year were the apparent catalyst for disciplinary action, Chambers's former boss, Donald Murphy, testified Wednesday that her problems with rules and authority began surfacing months earlier.

The circumstances surrounding one incident, in which Chambers was reprimanded for improper use of her police vehicle, became clearer when Chambers was cross-examined by government lawyers yesterday. She was not reprimanded for taking the car home, which she was permitted to do. Instead, she was cited for taking the car to North Carolina.

The cross-examination was brief. Robert D. L'Heureux, representing the Park Service, appeared to be using her testimony to simply establish some of the basic facts that the Park Service considers the essence of the case. He asked Chambers if she was indeed speaking in her official capacity when she talked to The Post last year, and she testified that she was.

Chambers also confirmed that she had received the agency's training in government ethics, in the form of an instruction manual that she had read.

A final witness, Deputy Interior Secretary James Steven Griles, is scheduled to testify Tuesday, before the two sides present their closing arguments to Administrative Law Judge Elizabeth B. Bogle.

Chambers said she "believed I was doing what needed to be done."