The Justice Department overreached in prosecuting a former Bush administration official in the Jack Abramoff lobbying scandal, a federal appeals court said Tuesday as it dismissed some charges and ordered a new trial on others.

The decision overturns the conviction of David Safavian, the former chief of staff for the General Services Administration and the only person in the four-year scandal who opted to go to trial rather than accept a government plea deal. He had faced 18 months in prison.

The ruling also forces prosecutors to decide whether to bring a new case or accept defeat in what had been an early victory in the corruption investigation.

Safavian was convicted of lying to Senate investigators, GSA ethics officials and the agency's inspector general about his relationship with Abramoff. The lobbyist was interested in government-owned properties and Safavian provided inside information about them.

He also joined Abramoff on a now-notorious 2002 golf junket to Scotland, along with Rep. Bob Ney and his chief of staff. The trip became a symbol of Abramoff's access to Capitol Hill and the lavish gifts he used to maintain it.

The U.S. Court of Appeals for the District of Columbia Circuit threw out two charges against Safavian, saying there was no legal basis for them. The court said Safavian was not required to volunteer information about his relationship with Abramoff when cooperating with the inspector general's investigation or when asking for a nonbinding ethics opinion.

"The government essentially asks us to hold that once an individual starts talking, he cannot stop," the appeals court wrote. "No case stands for that proposition."

The court also overturned Safavian's conviction on charges he lied to Senate investigators when he told them Abramoff did not do business with the GSA. Safavian argued that he was being honest, since Abramoff had no contracts with the agency.

The appeals court said the trial judge should have allowed Safavian to call an expert to discuss how government officials view this issue. Such testimony would have to be allowed if prosecutors decide to bring the case again.

"The government was overzealous in its original prosecution," attorney Barbara Van Gelder, who defended Safavian at trial, said. "I hope they exercise more discretion in deciding whether to retry him."

She said the original case stemmed from a Justice Department effort "to squeeze David" for information. When he didn't cooperate, she said, prosecutors used his case to send a message to others.

"Clearly if you don't cooperate, you'll have the full wrath of the government on you," she said. "And that full wrath, having lived through it, is pretty powerful."

That threat has typically worked in the Abramoff investigation. Abramoff himself cut a deal with prosecutors. In exchange for leniency when he is sentenced this fall, he agreed to cooperate against the people he once bribed.

Prosecutors also secured guilty pleas from Capitol Hill staffers to help send Ney, a former Ohio Republican, to prison. They won guilty pleas from former Deputy Interior Secretary Steven Griles and his girlfriend, Italia Federici, whom Abramoff used as his go-between to Griles.

Recently, a one-time top aide to former Rep. Ernest Istook, R-Okla., pleaded guilty to a conspiracy charge. Istook is referred to but not named in court documents. Also discussed in the documents is a former aide to Rep. John Doolittle, R-Calif., who remains under investigation.

"We hope that the government, having now successfully prosecuted a range of other officials, will not feel it's necessary to come back and knock on David's door," Safavian's appellate attorney, Lawrence S. Robbins said.

The Justice Department said only that it was reviewing the opinion Tuesday and did not say what it planned to do.

"David Safavian has been destroyed by this," Van Gelder said. "He has been debarred. He's been unemployable and he's been seen as a villain. This is vindication. Enough is enough."

Judge A. Raymond Randolph, who was appointed by the first President Bush, wrote the court opinion. He was joined by Judge Harry T. Edwards, an appointee of President Carter, and Judge Judith W. Rogers, who was appointed by President Clinton.