Former White House intern Monica S. Lewinsky commanded the spotlight again yesterday as she took the witness stand in Howard County to help bolster Maryland prosecutors' wiretapping case against her former close friend Linda R. Tripp.

The first public courtroom appearance by Lewinsky took place far from the White House and Pentagon, where she worked, and the Watergate apartment complex, where she took refuge for months.

Shortly after 8 a.m., Lewinsky walked into Circuit Court Judge Diane O. Leasure's stately courtroom in the old stone building overlooking historic Ellicott City and confidently and comfortably spent the next 75 minutes answering lawyers' questions.

There was no confrontation with Tripp--she has waived her appearance at the hearing on what evidence can be used against her when she goes on trial Jan. 18. But Tripp's 25-year-old son, Ryan, was there, sitting in the fourth row, straining to hear Lewinsky's every word.

Though the charges against Tripp concern a gossipy conversation with Lewinsky that Tripp allegedly recorded on Dec. 22, 1997--and then allegedly disclosed illegally to Newsweek magazine--the tape was not played and the questions focused on how Lewinsky claims to pinpoint the date of their discussion.

Tripp was indicted on the two charges in July; each carries a maximum sentence of five years in prison and a $10,000 fine.

Tripp's attorneys are trying to have much of the state's evidence excluded from her trial, arguing that Lewinsky and other prosecution witnesses learned about the recording from former independent counsel Kenneth W. Starr's office after Tripp began cooperating under a grant of immunity. Evidence obtained from someone who has been given immunity cannot be used against the person in court.

But Lewinsky testified that she hadn't needed any prompting from Starr's office to remember vividly the call that turned her private affair with President Clinton into a public spectacle.

"I was pretty upset," Lewinsky testified, when asked what she thought as she read a transcript of the call in the Feb. 2, 1998, issue of Newsweek. "In this issue, there was the transcript of . . . my conversation with Linda Tripp from Dec. 22, 1997, and I think that was pretty frightening to me."

Lewinsky arrived at the courthouse about 7:45 a.m., slipping through a side door and avoiding the more than 80 cameras and reporters who had been camped out in front of the landmark structure since long before dawn.

At 8:12 a.m., Deputy Maryland Attorney General Carmen M. Shepard announced, "The state calls Monica Lewinsky to the stand."

Several long moments passed. Reporters sat with their pens poised above their notebooks. Leasure smiled to the crowd and held up her hands as if to ask, "Where is she?" just before Lewinsky emerged from behind a gray door in the back of the courtroom.

"Hi," she mouthed with a smile to the judge before placing her large, black- and gold-patterned shoulder bag on the floor of the witness stand, sat down and tucked her shoulder-length black hair behind her ears.

Although the appearance of Lewinsky, 26, packed the courtroom, almost everyone in the crowd was associated with a news organization or worked in the courthouse.

Lewinsky testified that she was certain of the taped phone call's Dec. 22, 1997, date as soon as she read the Newsweek transcript headlined "Monica's Story."

The Dec. 22, 1997, date is key to the state's case because it would mean that Tripp made the tape after prosecutors say a lawyer warned her that it was illegal to record the calls without Lewinsky's consent.

The conversation had to have taken place after Dec. 19, 1997, Lewinsky said, because that's when she received a subpoena to testify in Paula Jones's sexual harassment lawsuit against Clinton. In the recorded call, Tripp and Lewinsky discussed a plan for Lewinsky to avoid testifying by saying that she needed foot surgery.

Lewinsky testified that in the same phone call, she told Tripp about just having spoken to presidential friend Vernon Jordan, whom she recalled talking to on Dec. 22, and mentioned that her farewell party at the Pentagon was to be held the next day, Dec. 23.

Lewinsky said she remembered being "terrified" at the time of the phone call because the Jones subpoena made her "concerned about the privacy of my relationship [with Clinton] being revealed."

But during cross-examination, Tripp attorney Joseph Murtha pressed Lewinsky on whether she identified the date of the call before or after she began cooperating with Starr's office under her own federal grant of immunity.

The tapes were not dated when Tripp gave them to the office of the independent counsel, Murtha said. Lewinsky signed her initials to attest that the recording dates attached by federal prosecutors were accurate only after reviewing the tapes in Starr's office, he said.

"You didn't give them the information," Murtha told Lewinsky, "they gave it to you."

"That's correct," she answered.

Though hardly attracting as much attention as Lewinsky, perhaps more important to the state's case was testimony yesterday from another former intern.

Gavin Patashnick, a former law clerk for State Prosecutor Stephen Montanarelli, was questioned by Tripp's attorneys about a memo he prepared for his boss summarizing the Starr Report to Congress. Montanarelli testified earlier this week that he never read the memo or the Starr Report.

Patashnick conceded that he gave a state investigator background details, based on his readings of news clippings, about a former co-worker of Tripp's. The witness, Mary Katherine Friedrich, later told state investigators that Tripp mentioned the tapes to her around Christmas of 1997--after Tripp was told the recording was illegal.

Lewinsky said she gave Friedrich's name to state prosecutors after she learned the woman's last name from Starr's office. Friedrich is to be called to testify today.

But even before Patashnick took the stand, the star witness had departed. This time she found a throng of cameras and reporters waiting at the side door.

"Monica, how was it?" someone shouted. She said nothing before ducking into the back of a gold Nissan Quest minivan and being driven away by state investigators. Shortly after noon, she was on a plane back to New York.