LOS ANGELES – The top accountant for a Hollywood gala to benefit Senator Clinton’s 2000 campaign testified yesterday that two days before the celebrity-studded concert, Mrs. Clinton’s national finance director dropped his estimate of the event’s cost by nearly $100,000.

The former fund-raising chief, David Rosen, is on trial in federal court here on charges that he caused the filing of campaign finance reports that deliberately understated the cost of the August 12, 2000, fund-raiser.

The woman who prepared those reports, Whitney Burns, took the witness stand yesterday for the prosecution.

“David had said that he had been trying … to whittle the costs down and to get the costs down,” Ms. Burns said. “He said that he thought the expenses had dropped.”

Ms. Burns said she and Mr. Rosen agreed to revise a line item for projected in-kind gifts in connection with the gala from $468,000 to $375,000.

Mr. Rosen’s alleged claim that costs were coming in well below the early budgets is starkly at odds with the testimony of numerous witnesses who have said Mr. Rosen and other planners of the gala were deeply concerned that the costs of the Hollywood-style bash were spinning out of control.

Ms. Burns told a prosecutor, Daniel Schwager, that she could not remember all aspects of the discussion, one of several she had by telephone with Mr. Rosen in the days leading up to the gala.

“My recollection of the conversation is very vague in terms of details about why, but he did indicate that he thought the costs had gone down,” she said.

Ms. Burns said she remembered one of the expense items Mr. Rosen told her could be omitted. “He mentioned that Cher had dropped out and that there wouldn’t be any band expenses for her,” said Ms. Burns, who was known as the compliance officer for the political committee that sponsored the gala, New York Senate 2000.

In fact, as jurors have already seen in videos of the gala, Cher attended the event and performed two songs.

Ms. Burns also testified that after the event, she asked Mr. Rosen for documentation for a $200,000 expense for the company that oversaw production of the concert. An invoice for that amount was later faxed to Ms. Burns from Mr. Rosen’s office. Earlier in the week, jurors heard from the owner of the company. He said he issued the invoice reluctantly and that it did not accurately reflect his charges, which were about $600,000.

Mr. Rosen’s lawyers have claimed he was in the dark about any spending or in-kind gifts beyond the amounts reported to the Federal Election Commission. On that account, Ms. Burns’s testimony yesterday was damaging to Mr. Rosen’s defense. However, she also described two decisions she made that could result in Mr. Rosen’s acquittal.

In the courtroom, the bookish Ms. Burns delivered a soliloquy about an issue of campaign finance law that has vexed the judge, the lawyers, and, likely, the jury. She attempted to explain the complex system used in 2000 and prior years to allocate donations and expenditures from a particular event between so-called hard money and soft-money accounts. While soft money could be received in any amount, it could not legally be spent directly on a federal campaign. Hard money had to be raised in smaller donations, but was preferred by political operatives because it could be spent directly on electing Mrs. Clinton or other federal candidates.

Ms. Burns said that before fund-raising events, she would transfer funds from the hard-money accounts to cover anticipated expenses. In the case of the gala, she decided, in essence, to transfer more money than was required by Mr. Rosen’s projections.

After the gala, Ms. Burns passed up an opportunity to reclaim some of that extra money for Mrs. Clinton’s campaign. “We could have transferred back the overpayment,” Ms. Burns said. The accounting expert said she could have made the transfer up to 60 days after the event but did not because she was still getting documentation for liquor, floral, and other expenses.

Lawyers on both sides of Mr. Rosen’s case agreed that, as a result of Ms. Burns’s decisions, Mrs. Clinton’s campaign did not benefit economically from the underreporting of expenses that Mr. Rosen is alleged to have caused. The defense hopes the absence of a concrete benefit or harm stemming from the episode will undercut the prosecution’s case.

Also testifying against Mr. Rosen yesterday was a New Orleans-based Democratic fund-raiser who is Senator Kennedy’s brother-in-law, Raymond Reggie.

Reggie said that after a walkthrough of the concert site the night before the gala, Mr. Rosen and one of Mrs. Clinton’s closest aides, Kelly Craighead, had a heated conversation about the event’s finances.

“They started into it pretty hard,” Reggie said. He said an “aggravated” Ms. Craighead wanted to know how much the gala was costing, how much it would make, and why it was so elaborate.

Reggie recalled that Mr. Rosen replied, “I’m the fund-raiser. I got it under control.”

Reggie said that, after the gala, Mr. Rosen complained that “the last minute costs crushed him.”

Reggie also said Mr. Rosen told him that the fee for the producer of the concert, Gary Smith, was more than $500,000, an amount far in excess of what was reported to Ms. Burns.

Reggie said Mr. Rosen and the promoter of the gala, Aaron Tonken, griped that Mr. Smith was charging “way too much money,” but that they had to use him because Mrs. Clinton insisted on it.

Last month, Reggie pleaded guilty to unrelated bank fraud charges. As part of his cooperation with the government, he surreptitiously recorded a dinner he had with Mr. Rosen in 2002.

Prosecutors chose not to use that recording in the case against Mr. Rosen and won an order from the trial judge, A. Howard Matz, barring the defense from revealing the contents of the conversation to the jury.

Judge Matz rebuked Mr. Rosen’s lead lawyer, Paul Mark Sandler, for defying the order by delving into that subject while cross-examining Reggie.

“Mr. Sandler, I don’t think you’re complying with the ground rules,” the judge said sternly after the jury left the courtroom for a break. “I don’t take kindly to that.”

Mr. Sandler apologized, adding that any violation was unintentional. The defense attorney also pointed out to jurors that Reggie was charged in 2002 with impersonating a police officer.

Reggie noted that the charge was recently dismissed. He said he holds several “honorary” commissions as a police officer.