Prosecution and defense attorneys took five hours yesterday in their final efforts to persuade a jury in the trial of three men charged with conspiring last year to assassinate prominent Iranian exile Ali Akbar Tabatabai.

In their closing arguments yesterday in D.C. Superior Court, three defense lawyers concluded their two-week effort to discredit the prosecution's star witness, Al Fletcher Hunter, also known as Abu Bakr Zaid Sharriff, a confessed coconspirator in the assassination, who testified under a grant of immunity. They also asserted that the government's case is based solely on that testimony.

"The only thing you've got is Hunter's testimony," defense attorney Ed Wilhite said. "Now that you know about him (Hunter) . . . if Mr. Hunter told you the sun was going to rise tomorrow, you would want to go out and check."

And, as they have for two weeks, the government prosecutors, Robert Ogren and Harold Cushenberry, insisted that there was ample evidence to support Hunter's testimony.

"No matter what deal he struck (to gain immunity from prosecution in this case and several bank robberies), the man was telling the truth," Cushenberry insisted.

The prosecution presented 40 witnesses and more than 100 items of evidence -- "the tidbits that tie the pieces together," Cushenberry said -- to corroborate Hunter's testimony. "All the way down the line, the evidence shows you a conspiracy existed . . . and the men charged were involved."

Tabatabai, a critic of the regime of Ayatollah Ruhollah Khomeini, was shot July 22, 1980, in the doorway of his Bethesda home by a man disguised as a postman. The alleged triggerman, David Belfield, also known as Daoud Salahuddin, a former security guard in the Iranian Interests Section of the Algerian Embassy, is not on trial. Authorities believe he fled the country after the killing and is living in Iran.

The three men on trial are charged with assisting Salahuddin in the killing and in making his getaway. Horace Butler, also known as Ahmed Rauf, allegedly helped Salahuddin obtain the U.S. Postal Service truck as part of a plan to pose as a mailman. He also is charged with disposing of the murder weapon, a 9mm pistol. Prosecutors have contended that Butler's apartment was the launching pad for the conspiracy.

Ali Abdul-Mani, also known as Lee Curtis Manning, is charged with renting the getaway car that Hunter allegedly used to drive Salahuddin to Montreal for connection with a flight overseas. Abdul-Mani also has been charged with lying to a grand jury when he testified that he did not lend the car to Salahuddin and was not reimbursed for it.

William Caffee Jr., also known as Kalid, is charged with helping abandon the car in the District.

In an unusual move, Judge Fred B. Ugast granted requests by Rauf and Abdul-Mani to address the jury briefly as co-counsel, without having to testify under oath.

Both said Hunter's testimony was implausible. "Does it make sense to risk everything in one's life for $100 (the amount Salahuddin allegedly gave Rauf) in such a haphazard plan?" Rauf argued. Abdul-Mani argued that the "government's zeal for a conviction leads them to overlook" that he lost $73 from the car rental. If a crime is political, he argued, then "people proudly proclaim" responsibility for their acts, something which none of the defendants in this case did.

Prosecutors have emphasized throughout the trial that Tabatabai was killed because he was a critic of the Khomeini regime, and that Salahuddin was a follower of Khomeini.

The case is expected to go to the eight-woman, four-man jury today.