Diane P. Jones thought about wearing an old pair of blue jeans to federal court last month in an effort to avoid being picked for the jury that would decide the fate of millionaire Dominic F. Antonelli Jr. and District political figure Joseph P. Yeldell.

"I didn't want to be locked up for three weeks," she said, referring to the time the jurors would be kept away from family and friends in a Washington motel during the trial.

But instead of wearing clothing that might have drawn attention and a possible disqualifying challenge from defense of prosecuting attorneys, the 27-year-old Amtrak accounting clerk showed up in court in a neat, conservative outfit. She was the first juror chosen.

Last night Jones had another reason for wishing she had never been picked for the jury. Because she failed to disclose that she once had an account in the Madison National Bank, which was founded by Antonelli, Judge Gerhard A. Gesell declared a new trial for Antonelli and Yeldell.

Her younger sister, Deborah, said that Diane Jones had used the account only a short time when she had a temporary job around the corner from the Madison National Bank.

"If she had had an account now she certainly would have told the judge," Deborah quoted her sister as telling the family after the judge's decision.

"But she had forgotten all about it. She has had accounts with several banks since them," the sister continued.

Yeldell's supporters, jubilant at the news of a new trial, criticized the jury's quick verdict in the complicated case.

The Jones family lives in the Petworth section of upper Northwest Washington. Her father, John H. Jones, is a parking attendant who once was fired from a job on a lot owned by Antonelli's firm, Parking Management Inc. - bringing about the first defense call for a new trial on grounds that Diane Jones had failed to disclose that fact at the time of jury selection.

Antonelli's lawyer, Edward Bennett Williams, argued that Jones "recognized, consciously or unconsciously, an opportunity to settle an old family score."

Both Diane Jones and her father steadfastly denied she had ever known her father had been fired by PMI and Gesell said yesterday that he believed her. It was the new information about the bank account that brought about Gesell's ruling for a new trial.

Diane Jones graduated from Western High School and has been working for Amtrak for about three years.

Before that, her sister said, she had worked for Kay's Jewelers, but was laid off and forced to take the temporary job that placed her around the corner from a branch of the Madison Nation Bank.

As recently as yesterday morning, she told reporters in the federal courthouse corridors that she could not recall ever having an account at that bank.