The drug conspiracy and perjury trial of D.C. Mayor Marion Barry nears its final stage today as attorneys for each side square off in a war of words known as final arguments, their last chance to convince jurors that their version of events is the truth.

After two weeks of jury selection and six weeks of trial, the work of deciding whether the mayor is guilty of conspiracy, drug possession and lying to a grand jury is almost ready to begin. Final arguments are expected to take most of today. U.S. District Judge Thomas Penfield Jackson is expected to issue jury instructions tomorrow, and then the jury will get the case.

Jackson said earlier this week he plans to excuse the six alternate jurors after final instructions and before deliberations begin.

Prosecutors and defense lawyers spent most of yesterday working on their final arguments and wrangling over the wording of jury instructions on such issues as perjury, entrapment, immunized witnesses and the definition of conspiracy.

While jury instructions are the judge's purview, lawyers on both sides present arguments about the wording of the instructions.

The judge said the defense and prosecution each will have 2 1/2 hours to make its case. The government has not said which of the two prosecutors on the case, Assistant U.S. Attorneys Judith E. Retchin or Richard W. Roberts, will deliver closing arguments.

The government is expected to say that Barry was a longtime, chronic drug user, and that the FBI and D.C. police began investigating him only after they received evidence of his drug use.

The defense is expected to say that the government set out to get the mayor, then investigated many of his friends, and unfairly pressured them into becoming witnesses against him.

Lead defense attorney R. Kenneth Mundy will deliver closing arguments for the defense.

In a brief hearing yesterday afternoon, Barry co-counsel Robert W. Mance lost a bid to persuade Jackson to issue jury instructions on perjury that would have made it easier for the jury to acquit the mayor on one of the three perjury charges against him. Neither Barry nor Mundy was present for the hearing.

Mance had argued that if Barry answered a prosecutor's question correctly, then volunteered a statement the jury believed was false, the second part of the answer should not be considered "material" to the perjury charge.

Jackson disagreed in yesterday's hearing, relying on the closest legal precedent he could find: a U.S. Court of Appeals ruling from last year stating that a perjury conviction should be based on the meaning of a series of statements understood together.

The argument was relevant to an answer that Barry gave Retchin in the grand jury in January 1989 regarding Charles Lewis, a former D.C. employee who became the prosecution's chief witness.

At the time, Retchin asked Barry, "Have you ever talked with anyone else about Mr. Lewis's involvement with cocaine?"

Barry answered, "I'm hesitating because I don't -- I doubt if I did because I don't know of any involvement he had with cocaine."

Mance had argued that Barry's response to the question -- "I doubt if I did" -- was literally correct, and that the jury's conclusion about the truth or falsity of the rest of the sentence should be irrelevant.

But Retchin told Jackson, "The government's position is that you can convict a defendant for making false statements {before a grand jury} even if the statement is volunteered."

Jackson agreed, but indicated that he would not decide on the exact wording of the perjury instruction until today.

He also rejected Mance's contention that the jury should be told that the government was obliged to prove that Barry was part of a single, organized conspiracy to possess cocaine -- an assertion that would be difficult to substantiate because many of the alleged co-conspirators in the case did not know each other. Retchin countered that Barry should be considered the hub of the conspiracy, providing the link that tied together everyone else named as a co-conspirator, whether they knew each other or not.

"I think that's correct, Mr. Mance, I really do," Jackson said, referring to Retchin's argument.

But the judge approved Mance's request that he tell jurors that if the transcript of the tape of the Vista Hotel drug sting varied from what they heard, they should rely on their hearing and not the transcript.