Defense lawyer R. Kenneth Mundy gave the jurors in the mayor's case a full-throated rendition yesterday of themes of outrage and suspicion he had been able only to hint at up to now.

For the first time in the trial, the prosecution responded in kind. Assistant U.S. Attorney Richard W. Roberts, arising as if unchained after eight weeks of restraint, raised his voice in rich and righteous emotion. He entreated the jurors to "rise up to your responsibilities," and offered "no apologies" for the government's labors in holding Mayor Marion Barry responsible for his conduct.

The two sides' last words to the jurors, though contradictory in substance, had a single strategic aim: to bolster their supporters for the battles to come as deliberations begin in the jury room.

"This is about emotions," Mundy said in a lunch-time interview. "I'm trying to give them a reason, if they're for me, to stick by their guns."

For all the folklore about them, surprisingly little is known of the decision-making methods of criminal case jurors. Conventional wisdom among lawyers is that individual jurors form their views long before the closings in a case. Many lawyers therefore conceive of closings, as lawyer Abbe D. Lowell said in an interview, less as tools to persuade the undecided than as opportunities to give their supporters on the jury "the courage of their convictions."

"If he doesn't do that," Lowell said of Mundy, "and if it's nine to three {in the jury room} for conviction, the three will cave. If he does do that, the three will hold out forever."

Apart from seeking to motivate his supporters, Mundy lost no chance yesterday to tell them which counts mattered most in Barry's indictment.

Walking right up to the line of the permissible -- some judges might have said he crossed it -- Mundy signaled the jurors three times that possession of drugs is a misdemeanor, "the mildest form of crime known in our set of laws," but that perjury is a felony, likely to lead to a substantial prison sentence.

Mundy even cited mistaken testimony by Charles Lewis -- which he elicited more than a month ago for just this purpose -- that perjury carries a 10-year prison sentence. As Mundy knows, but jurors do not, the maximum sentence for perjury is five years, and under binding sentencing guidelines the actual sentence is certain to be shorter.

U.S. District Judge Thomas Penfield Jackson, in an instruction that is standard in federal cases, told the jurors yesterday that "the question of possible punishment of the defendant in the event of a conviction is of no concern to you, and should not enter into or influence your deliberations in any way." Few lawyers believe such instructions are universally obeyed, and Mundy appears to hope that this one will not be.

The imagery of Mundy's closing, like the tone of his cross-examination throughout the trial, was thick with intimations of foul play against his client.

In Mundy's version of the evidence, there were payoffs to such witnesses as Hazel Diane "Rasheeda" Moore, whose $1,700 a month in witness protection support provided "pretty good incentive . . . to fabricate" what the government wanted to hear; there were drug dealers and other criminals confronted with "the friendly hand of the FBI saying, 'Take hold, and pull Marion Barry into the quagmire in your place' "; there were law enforcement officials "watching through the peephole" and permitting Barry to ingest a dangerous drug; and there were sinister gaps in the evidence, with missing audio portions of a video recording and incriminating objects found among Barry's possessions after days or months in government custody.

As Mundy has sometimes acknowledged, his trial strategy depended in part on a technique known to lawyers as nullification -- persuading jurors that they should not convict regardless of the weight of the evidence. It is not an argument that may be openly made.

In echoes of his opening request, more than six weeks ago, that jurors consider their place in D.C. history, Mundy sought yesterday to strengthen the jury's sense of independence.

"Your decision cannot be reviewed or corrected anywhere," he said. "The decision you make today will go down in the books as the decision on the case . . . . What you do today when you wake up tomorrow you should be comfortable with."

Roberts, when he rose to reply, addressed precisely the jurors' sense of comfort. Just as Mundy had sought to stir anger at the government, Roberts held Barry up to ridicule and righteous contempt.

The prosecutor, who is black, used a mocking dialect version of Barry's words to mimic the mayor's televised claims that "never in my life have I used illegal drugs." As Barry said those words, Roberts told the jury, he "smoked and snorted his way" into 1989 and 1990.

The "heart of the defense," Roberts said, was "don't convict me because the government was out to get me" -- but Barry was in fact "out to get himself."

"He is asking you to let him insult your intelligence," Roberts said. "The defendant was exposed, pure and simple, and there are no apologies for having conducted an investigation in which these crimes have been exposed and Marion Barry's conduct has been exposed. Case closed."

Like Mundy, Roberts never mentioned nullification. But like Mundy again, he saved for last an appeal to the jury's deepest sense of mission.

"You must tell Marion Barry," he said, "that you will rise up to your responsibility to speak the truth . . . . And you must tell Marion Barry that he must rise up to his responsibility and to accept responsibility for his conduct before he can rise up again and reclaim his place in history."