LOS ANGELES – The national finance chief for Senator Clinton’s 2000 campaign, testifying in his own defense, told a federal court yesterday that he was entirely unaware that a celebrity studded fund-raising concert he helped organize cost hundreds of thousands of dollars more than what was reported to federal election authorities.

“These costs were hidden from me. These costs were concealed, for whatever reason, by the people that were putting this event on,” the former campaign aide, David Rosen, said.

Mr. Rosen, 38, who stands accused of causing the filing of false reports with the Federal Election Commission, took the stand as his trial entered its third week.

“I am 100% innocent of these charges,” Mr. Rosen declared to the jury.

In response to questions from his lead attorney, Paul Mark Sandler, Mr. Rosen said he had no knowledge of a number of specific expenses for the August 12, 2000, gala, which featured performances by Cher, Patti LaBelle, among others.

Contradicting a long line of prosecution witnesses, Mr. Rosen said there was no particular concern among the planners about spiraling costs for the star-packed event. He said he thought the expenses “were in line with the projections.”

Prosecutors contend that the event cost more than $1.2 million, but that less than half that amount was disclosed in campaign finance filings. Billed as a “Hollywood tribute” to President Clinton, the $1,000-a-ticket concert benefited Mrs. Clinton’s Senate campaign.

While other witnesses spoke about frantic efforts to secure private airplanes for famous guests, Mr. Rosen said the campaign was paying little or nothing for the performances.

“These celebrities lived in Los Angeles and were contributing their time. My understanding was these were direct, in-kind contributions from the celebrities,” he said.

Mr. Rosen said his main concern at the time was not the cost of the gala, but that the planning was too rushed.

“We did not have enough time to plan this,” he said. “I was very nervous about being able to pull it off, being able to have it ready by the time all of these important people came to the gala.”

At the outset of yesterday’s session, the judge presiding over the case, A. Howard Matz, dismissed one of the three felony counts pending against Mr. Rosen. Each of the counts relates to an allegedly false report or letter that the fund-raising committee responsible for the concert, New York Senate 2000,sent to the Federal Election Commission.

In striking the third count, the judge ruled that the prosecution had failed to offer evidence of Mr. Rosen’s connection to a letter the fund-raising committee submitted in July 2001.

If convicted on the remaining two counts, Mr. Rosen could face up to 10 years in prison and a fine of up to $500,000.

The trial appears to turn on a swearing contest that pits Mr. Rosen against most of the prosecution witnesses. While the testimony of any defendant, such as Mr. Rosen, is inherently questionable, jurors have also learned that two of the witnesses against him, Raymond Reggie and James Levin, are admitted criminals who have entered plea deals with the government.

Further complicating the case is the fact that the key financial backer of the gala, Peter Paul, and the main coordinator of the event, Aaron Tonken, are both convicted felons. Both sides declined to call them as witnesses.

Reggie, a New Orleans-based advertising consultant once friendly with Mr. Rosen, said the night before the gala he saw Mr. Rosen engaged in a heated argument with a top traveling aide to Mrs. Clinton, Kelly Craighead. The point of contention was the scope and cost of the concert, Reggie said. When Mr. Rosen was asked yesterday if he ever engaged in such a discussion, he said, “I did not.”

Neither side has called Ms. Craighead to testify.

Mr. Rosen also flatly denied complaining to Reggie or anyone else about costs for the gala. Reggie, who has pleaded guilty to two unrelated bank fraud charges, testified last week that Mr. Rosen griped about being “crushed” by last-minute expenses for the gala.

Mr. Levin, who has offered to plead guilty in a bribery and public contracting fraud scheme, testified that while touring the concert site in the lead-up to the event, Mr. Rosen said, “The costs of this event will never be the costs of this event.”

Mr. Rosen denied making that statement, as well. “I would never talk about the costs at a walk-through two days before the event,” he said.

Not all of those whom Mr. Rosen contradicted yesterday are disreputable. An event planner for the gala, Bretta Nock, said Mr. Rosen instructed her to strike line items from the budget to lower the costs being reported to Washington, D.C.

Asked yesterday if he ever made such a request, Mr. Rosen said emphatically, “Absolutely not.”

Mr. Rosen also addressed the testimony of a campaign bookkeeper, Whitney Burns, who said Mr. Rosen told her two days before the concert that a reduction in the budget was due to Cher dropping out. In fact, she performed two songs at the gala.

“I wanted to alert Whitney that Cher might bring a band and that’s what we talked about,” the former campaign aide said.

Mr. Rosen, who wore an olive suit and gold tie, seemed calm during the two-and-a-half hours he spent responding to his lawyer’s queries. The professional fund-raiser sometimes turned to the jury when asserting his innocence. The jurors, for their part, seemed more focused on the defense lawyer’s questions than the defendant’s answers.

However, within the first few seconds of cross-examination, Mr. Rosen stumbled. The lead prosecutor, Peter Zeidenberg, asked Mr. Rosen if he knew he was under criminal investigation in the summer of 2002 when Reggie invited him out to dinner. Reggie, who was cooperating with the FBI, secretly taped the meeting.

Mr. Rosen said he did not know of the criminal probe and knew only of a civil lawsuit related to the gala. “I didn’t know about the grand jury,” he said.

Mr. Zeidenberg then read from a transcript of the conversation. “There’s been a lot of stuff happening, man, the FBI, grand jury s–,” the prosecutor quoted Mr. Rosen as saying.

After further prodding, Mr. Rosen conceded that he did know about the criminal investigation when he saw Reggie in 2002. The concession was not central to the case, but may have undermined Mr. Rosen’s credibility.

While the defense led Mr. Rosen through a long series of questions about his family, education, and work background, the prosecution honed in on one aspect of that history: Mr. Rosen’s work as a salesman. One of Mr. Rosen’s first jobs was selling reference books door-to-door.

“It took some sales technique to sell those books,” Mr. Zeidenberg said. “You can sell, as far as you’re concerned, soap powder or a politician using the same skills?” the prosecutor asked rhetorically. His implication appeared to be that Mr. Rosen was engaged in a sales job directed at the jury.

The cross-examination of Mr. Rosen is to resume this morning.

Earlier yesterday, jurors heard from a critically-acclaimed television producer involved with the gala, Gary Smith. Mr. Smith bolstered Mr. Rosen’s case by denying that he ever talked about the cost of the event with the defendant. The television producer also disputed Mr. Levin’s testimony that he negotiated a $50,000 reduction in the production fee.

The prosecution showed Mr. Smith a page from his date book which referenced Mr. Rosen and a phone message that Mr. Rosen apparently left on the morning of the gala. Mr. Smith said he wasn’t sure he ever met Mr. Rosen during planning for the gala.

Mr. Zeidenberg asked Mr. Smith, who also produced the Democratic Convention days later, if he took on the gala at Mrs. Clinton’s request. “It was conveyed to you that Mrs. Clinton really, really wanted you to do this, correct?” the prosecutor asked.

Mr. Smith, looking ever the producer, with his glasses resting in his hair, agreed, but did not elaborate on how or by whom the request was relayed.

As he left the courtroom, Mr. Smith turned to a sketch artist covering the trial and gave her a big kiss.