Government prosecutors yesterday concluded their week-long presentation of witnesses in the D.C. Superior Court trial of three men charged with conspiring last year to assassinate prominent Iranian exile Ali Akbar Tabatabai, who was shot in the doorway of his Bethesda home by a man disguised as a mailman.

The prosecution has called 40 witnesses --ranging from FBI agents to car rental and airlines employes to Postal Service workers -- and produced about 100 items as evidence, in large part to buttress the testimony of its key witness. He is a coconspirator who was granted immunity in this case and in several bank robberies and other crimes in exchange for his testimony.

The witness, Al Fletcher Hunter, also known as Abu Bakr Zaid Sharriff, last week described how he and the alleged triggerman -- Daoud Salahuddin, also known as David Belfield -- set up the assassination and how he drove Salahuddin, a former security guard with the Iranian Interests Section of the Algerian Embassy here, to Montreal for a flight out of the country.

The three men on trial are accused of assisting Salahuddin both before and after the killing of Tabatabai, an outspoken critic of the regime of Ayatollah Ruhollah Khomeini. Ahmed Rauf, also known as Horace Butler, is charged with helping Salahuddin obtain a U.S. Postal Service Jeep as part of the ruse to lure Tabatabai to the door and with disposing of the murder weapon. Ali Abdul-Mani, also known as Lee Curtis Manning, is charged with renting the car that Hunter and Salahuddin drove to Montreal and also is charged with perjury for testifying to a D.C. grand jury that he did not lend the car to Salahuddin. William Caffee Jr., also known as Kalid, is charged with wiping fingerprints off the car after Hunter drove it back to Washington and with abandoning it.

Much of the prosecution's outline of the conspiracy hinges on testimony by Hunter, whose credibility and motives have been challenged by defense attorneys. The attorneys have repeatedly asserted that Hunter has been granted immunity despite an involvement in the assassination that is greater than any of the men on trial.

For that reason, prosecutors have introduced evidence ranging from notes in Salahuddin's handwriting found in Rauf's apartment -- one with directions to Tabatabai's home, another with a series of dollar amounts for a car rental and apparently for paying a postman for use of the Jeep-- to a car rental agent who testified that Abdul-Mani reported the getaway car stolen a week after the killing. Prosecutors hope to show that the detailed corroborating evidence will convince the jury that Hunter was telling the truth.

The 12 jurors and five alternate jurors in the case, who are sequestered in an area hotel, will spend Thanskgiving there. Judge Fred Ugast will permit the jurors' family members to visit them for Thanksgiving dinner.