WASHINGTON – A former flight attendant who finished law school at 36, Carla Martin seemed to be at a pinnacle of success when it all came crashing down this week.

She earned a six-figure salary. She traveled extensively. And she played an important role in a courtroom drama watched by millions around the globe: the death penalty case of confessed Al Qaeda conspirator Zacarias Moussaoui.

Then, suddenly, she was looking at the possibility of disbarment, a stiff fine, even prison.

“She’s really completely torn up,” said her mother, Jean Martin Lay. “How could it happen?”

In court on Tuesday, U.S. District Judge Brinkema said that Ms. Martin violated federal witness rules when she sent trial transcripts to seven aviation witnesses, coached them on how to deflect defense attacks and lied to defense lawyers to prevent them from interviewing witnesses they wanted to call.

Judge Brinkema warned her that she could face civil or criminal charges and that she appeared to have violated rules of legal ethics.

Ms. Martin was assigned to be a government lawyer for the aviation witnesses called by both sides and to be a liaison between prosecutors and defense attorneys. Beyond that, she co-signed one government brief submitted in the case, attended closed hearings on classified documents and worked closely with prosecutors on preparing their exhibits.

Yesterday, Ms. Martin, 51, was placed on paid administrative leave from her job as a Transportation Security Administration attorney, where she earned about $120,000 a year.

Efforts to reach her for comment were unsuccessful, but her attorney, Roscoe Howard, said she was preparing a response.

“Only her accusers’ stories have been told, and those stories have been accepted as the whole truth,” Mr. Howard said yesterday. “They are not.”

Judge Brinkema said that Ms. Martin’s actions and other government missteps had left the aviation evidence “irremediably contaminated.”