In the final analysis, jurors in the federal bribery and conspiracy trial of former city official David E. Rivers and D.C. contractor John B. Clyburn said the government kept throwing what one called "bits and pieces" of evidence at them, but failed to put the puzzle together to adequately prove its case.

"There was not enough evidence, and we could not fill in the gaps or read into the minds {of the defendants}," said juror Karen Silver, who added that the government "just didn't have it . . . . There was doubt in my mind, and I just couldn't go with a guilty {verdict}."

Silver and three other jurors also said they believed the FBI pushed too hard during its undercover sting seeking evidence of corruption in the city's contracting process, although this was not a decisive factor in their verdict.

"The FBI," said Silver, "went beyond the call of duty."

U.S. Attorney Jay B. Stephens said yesterday that prosecutors believed "the evidence in the case demonstrated a classic pattern of contract fraud."

"While there may not have been a single smoking gun, that is not how corrupt business transactions are conducted," he said. "They involve a sophisticated pattern of activity."

The acquittal of Rivers and Clyburn marked the finale of one of the government's broadest and most heralded investigations of alleged District government corruption.

It began in 1986 with a 17-month undercover FBI sting operation -- revealed in a flurry of subpoenas and front-page headlines in May 1987. The probe broadened, focusing on nearly every major city agency, top city officials and numerous city contractors.

Although Mayor Marion Barry was not a formal target of the probe, few doubted that federal investigators had viewed the probe as their best chance of linking the mayor to contract irregularities.

When Clyburn was acquitted on Monday, four days after the same jury acquitted Rivers, critics of the federal prosecutors were quick to say the government had overreached.

It was a message Barry and his supporters trumpeted as the mayor's federal drug and perjury trial continued in a courtroom four floors below in the same federal courthouse.

Barry issued a statement contending that the U.S. Attorney's Office had "waged a long and underhanded campaign to discredit the minority business community in Washington."

Last Thursday, after Rivers was acquitted, Barry said he was delighted the jury had rejected "the overreaching, overzealous U.S. government and U.S. Attorney's efforts to discredit the Barry administration and ruin people's lives and reputations."

Calvin Rolark, a weekly newspaper publisher and longtime friend of the mayor's, said the government had been "overzealous, hoping to link the mayor . . . in this case by virtue of the fact that the mayor appointed Rivers and they were close friends."

Rolark said the government was going for "the one-two punch," attempting to show Barry's inefficiency for placing Rivers in a top job.

But the verdict, Rolark said, shows that "justice is evenhanded" and that the system "is working."

When the government's D.C. contract investigation first surfaced as front page news in 1987, the mayor alternately derided the probe as a "Mickey Mouse kind of operation" and lambasted it as a racially motivated assault on his predominantly black administration.

After he was acquitted, Clyburn said there were "racial underpinnings to the case," as authorities unfairly put "too much emphasis on minority contractors."

Stephens said yesterday, "The victims of the crimes alleged were not only the taxpayers, but other minority contractors who were shut out of the contracting process because it was unfair."

Three jurors interviewed since the verdict said that racial issues never came up during their nearly 40 hours of deliberation. However, jury foreman Thomas McLean said Monday that he suspected two jurors felt the prosecution might have been partly motivated by race, but he did not elaborate.

"I think we all accepted that the FBI was going after minority contractors in the D.C. government," McLean said.

Clyburn, a minority businessman, and Rivers, former head of the city's Department of Human Services, were charged with manipulating the contracting process over a four-year period to benefit themselves and their friends. The alleged scheme involved a pattern of stacking contract evaluation panels, leaking confidential bid information and corrupting other D.C. officials.

The government presented dozens of witnesses and 1,000 exhibits, including 300 secretly taped conversations, to show a pattern of alleged corruption.

Throughout the 16-week trial, the defense argued that Rivers was simply trying to help minority firms obtain work, and Clyburn was doing savvy business networking -- all within the bounds of legality.

McLean said that at one point in the jury's deliberations, he mentioned that the FBI might have entrapped the two defendants. No one agreed, McLean said, but jurors were critical of the agency.

"They {the FBI investigators} were wasting their time and . . . a lot of money," said McLean. "It took them too long to find nothing."

Three other jurors said the undercover FBI agent, who posed as a wealthy businessman seeking D.C. contracts, pushed too hard, particularly in secretly taped conversations with Rivers. The government charged that Rivers agreed in those 1987 conversations to accept future benefits from the agent in return for lucrative contracts.

One juror, who asked to remain anonymous, said, "The FBI offered more things than I can count on two hands to this man {Rivers} and he never accepted."

The FBI agent "was constantly pushing," said Silver. After nearly two years of undercover work, "I think they {the government} should have had a little more than they had -- which was absolutely nothing," she said.

However, juror Louise Stevenson disagreed that the FBI agent had pushed too hard. "No, he was just doing his job, trying to get him {Rivers} to agree to things," she said.

According to Silver, by the time deliberations were over, she wondered why the government had brought the case.

Some of those who watched the trial from afar said that all the second-guessing of the government's case and motives is pointless.

Joslyn Williams, a prominent labor leader and head of the D.C. Democratic State Committee, said that some people "may see all manner of conspiracies" in the fact that the government mounted the prosecution and lost, but, "I'm satisfied the government thought it had a good case."

He said that seeking racial or ethnic motives "isn't relevant anymore and we ought not to lose ourselves in that."Staff writers Nancy Lewis and Daniel H. Pink contributed to this report.