DENVER, SEPT. 25 -- One witness invoked the Fifth Amendment 14 times and another refused to appear voluntarily as a hearing began today on conflict-of-interest allegations against Neil Bush, the president's son.

Outside, the federal courthouse was surrounded by news media, security officers and protesters.

The only thing missing in the savings and loan case was the center of all the attention. Neil Bush, 35, did not show up for the first day of what is anticipated to be a four-day proceeding before Administrative Law Judge Daniel J. Davidson.

"He has the option of being here. He only has to be here the day he testifies," said Tom Mason, a spokesman for the Office of Thrift Supervision (OTS). Bush is the last witness and is expected to testify at the end of the week.

The OTS is trying to bar Bush from the banking and savings industry for his alleged actions as a director of Silverado Banking, Savings and Loan, which failed in late 1988 at a cost to taxpayers of $1 billion.

At today's hearing, Michael Wise, Silverado's former chairman and chief executive officer, invoked his Fifth Amendment right to refuse to answer questions on the grounds that he could incriminate himself.

Davidson then allowed him the opportunity to testify in his chambers in order that Wise be "spared the ordeal of going through a futile gesture of taking the Fifth."

But a transcript released later in the day showed Wise still refused to answer any of the 14 questions he was asked. Those questions ranged from whether he could identify exhibits to his knowledge of Bush's business ties to two Denver developers who eventually defaulted on Silverado loans exceeding $130 million.

Meanwhile, Florian Barth, a former Silverado board member and a Denver car dealer, said today that he refused to testify voluntarily. The judge said he would sign a subpoena to bring Barth to court if either side requested one.

Federal regulators accused Bush last February of violating his duty as a Silverado director from August 1985 to August 1988. The OTS claims Bush may have improperly voted on loans and lines of credit for developers Kenneth Good and Bill Walters, both of whom contributed to Bush's JNB Exploration oil company. The two defaulted on Silverado loans totaling more than $130 million.

Last week, Bush and other former Silverado directors also were sued for $200 million by the Federal Deposit Insurance Corp. The lawsuit alleged that gross negligence on the part of Silverado directors contributed to the S&L's collapse.

Bush could have avoided this week's hearing by agreeing not to dispute the charges, as other S&L officials have done. By fighting the government, he has taken the case into a rare public forum.

Russell Murray, former Silverado executive vice president, was the first scheduled witness to actually testify today. He reviewed a 1986 proposal for a $900,000 line of credit for Good International Inc., which wanted to search for oil in Argentina with Bush's JNB as a partner. Murray said he did not recall anyone questioning the no-collateral line of credit even though Good and Bush had a business relationship. He indicated the line of credit was for show only.

Later, J. Donald Wright, chairman of Lakewood Bank and Trust of Dallas, was called by the government as an expert witness to give his opinion of Bush's role in approving $100 million in loans to Walters. Walters had invested $150,000 in Bush's company and his bank gave Bush's company a $1.75 million line of credit.

"Mr. Bush should have disclosed his relationship with Mr. Walters" when the Silverado board voted on the loans, said Wright. "He was obligated to Mr. Walters. It would have been difficult to move to defeat Mr. Walters's loan," he said. "Mr. Bush is responsible for that judgment."