A federal jury early this evening convicted Washington lawyer William A. Borders Jr. of conspiring with a U.S. District judge in Miami to take a $150,000 cash bribe from a man he thought was one of two brothers convicted of racketeering in the judge's courtroom.

Borders, seated in his chair at the defense table with his lawyers, showed no reaction when the courtroom clerk announced that the seven men and five women of the jury had found him guilty on all four charges against him after only 65 minutes of deliberation.

Borders, free on $25,000 bond, left the courthouse quickly after the verdict was announced, quietly telling reporters that he would have no comment on the verdict. One of Borders's defense lawyers said the conviction would be appealed.

A member of the D.C. commission that selects local judges, he was convicted of conspiracy to commit bribery, obstruction of justice and two counts of interstate travel to commit bribery. He faces up to 20 years in jail and possibly thousands of dollars in fines.

During the six-day trial, the jurors heard 15 secret tape recordings, including three conversations between Borders and an FBI undercover agent and a telephone call between Borders and U.S. District Court Judge Alcee L. Hastings of Miami that was taped through a court-authorized wiretap. In one of the meetings with the undercover agent, Borders took a $25,000 down payment on the bribe.

Justice Department prosecutor Reid H. Weingarten told the jurors in closing argument today that those tapes, plus testimony from government witnesses, proved that Borders, with help from his friend Hastings, "put justice up for sale in a cold and calculated scheme."

After the verdict was returned, jury foreman Willard Camp told reporters, "To us it was just an overwhelming case." When asked what most persuaded the jury to reach its verdict, Camp replied, "Everything."

The jury's decision here today does not directly affect Hastings, who will be tried separately in Miami. But to convict Borders of conspiracy, an act whose legal definition involves action by more than one person, the jury had to feel convinced that Hastings was a willing and knowing participant with Borders in the bribery scheme.

Hastings' lawyer, Andrew P. Mavrides, who had attended the Borders trial, left the courtroom as the jury was polled and telephoned Hastings. Mavrides said Hastings told him, "Now you can come home."

Judge Edward T. Gignoux of Portland, Me., who presided over the trial by special designation, scheduled sentencing for May 7 at the federal court here. Gignoux, who was assigned to the case after all federal judges in Miami recused themselves because of the alleged involvement of one of their colleagues, said Borders could remain free on the $25,000 bond that was posted after his arrest last October.

John A. Shorter Jr., who represented Borders along with Atlanta lawyer Marvin Arrington, said he was surprised at the jury's swift decision. Borders' trial was moved here, at his request, because of extensive pretrial publicity in the Miami area.

Arrington, who is also president of the City Council here, said, "We're disappointed. The process has worked. We'll have to live with it."

During the trial, Justice Department attorneys Weingarten and Robert I. Richter argued that Borders acted as a middleman for Hastings. The government charged that in exchange for the money that Borders received from the man he thought was Frank Romano, Hastings returned $845,000 that he had ordered Frank and Thomas Romano to forfeit and also intended to reduce three-year prison terms he had imposed on each of them.

The Romano brothers had been convicted in December 1980 after a lengthy jury trial of 21 counts of racketeering, tax and mail fraud.

Shorter tried to diffuse the conspiracy charge by disassociating Borders from any actions taken by Hastings. Shorter also suggested that Borders was only pretending that he could influence Hastings in an effort to get money from the man he thought was Romano.

The investigation of Borders and Hastings began last summer when an informant and former client of Borders, Miami antique dealer William Dredge, told the FBI that Hastings was soliciting payoffs from defendants who had appeared in his courtroom.

Former FBI agent H. Paul Rico, 57, who is now general manager of a jai alai operation in Miami, was called out of retirement to pose as Frank Romano.

Rico, wearing a stereo recorder concealed under his clothing, was introduced to Borders by Dredge and subsequently met three times with Borders. All of the meetings were recorded.

Those tape recordings, plus 12 more tapes of telephone conversations obtained through court-authorized wiretaps, were the core of the government's case against Borders.

At the first meeting on Sept. 12, Borders said in the tape, "I think we can help you," and later wrote "$150,000" on an envelope he pulled from his pocket. Borders told the agent he wanted what the agent called "up front" money and then planned a second meeting for Sept. 19.

As a demonstration of his influence with Hastings, Borders told Rico to pick a restaurant for Hastings to eat dinner at a designated time. According to the government's evidence, Hastings appeared at the Fontainebleau Hilton Hotel in Miami Beach on Sept. 16 as Borders had guaranteed.

At the second meeting at the Miami airport on Sept. 19, Borders accepted $25,000 in cash from the undercover agent. According to government testimony, the $25,000 has not been seen since. On the tape recording, Borders promised that within 10 days Hastings would sign an order releasing the $845,000 that the Romano brothers had forfeited.

Hastings signed that order on Oct. 6, 15 days after Borders had made the promise to the FBI agent. A former law clerk of Hastings testified during the trial that the order had been unattended for several months, but that on Oct. 5, Hastings told him, "I want the order today."

On Oct. 5, Hastings also telephoned Borders at his law office in Washington on New Hampshire Avenue NW.

"I've drafted all those, ah, ah, letters, ah, for him . . ." Hastings said on the tape.

"Um hum," Borders replied.

The third meeting took place three days later, Oct. 9, at the Marriott Twin Bridges Hotel in Arlington. It was at that meeting that Borders was arrested.

Borders is a graduate of Howard University Law School. His career as a criminal lawyer has centered in the local and federal courts in Washington where he has represented a variety of clients, including defendants in drug and gambling cases.

In 1980, he served as president of the National Bar Association, which represents many of the the nation's black lawyers. Borders was an early supporter of former president Jimmy Carter, was a member of one of his campaign finance committees and raised thousands of dollars in Carter's 1976 and 1980 election campaigns.

It was Carter who appointed Borders to the D.C. Judicial Nomination Commission, which sends nominees for local trial and appellate judgeships to the White House for consideration.

Last summer, the Reagan administraton tried to remove Borders from that commission, in favor of a candidate supported by the Republican White House. Borders filed a lawsuit to stop his ouster and a U.S. District Court in Washington agreed that he could not be removed from the commission. That case is now before the U.S. Court of Appeals.

Borders stepped aside from commission activities after his arrest, but he did not resign.