Seventeen prospective jurors were examined in the drug and perjury trial of D.C. Mayor Marion Barry yesterday, the sixth day of a two-week procession of community values and prejudices.

The panelists were at loggerheads on fundamental questions of fact and moral belief: the fairness of undercover surveillance, the medical basis for substance abuse, the ethics of lying under oath, the credibility of the mayor and government witnesses.

Some felt so strongly about one or another question that Judge Thomas Penfield Jackson excused them from further service. Virginia C. Graham, a white woman who appeared to be in her fifties, disqualified herself with her very first answer to the judge.

Jackson asked whether she had formed any opinions about the facts of the case. Graham paused at some length, and when she spoke her voice was tight with tension.

"I would not be able to support the defense in any way," she said. "My leanings are for the prosecution."

"So you do not think you could be a fair juror?" Jackson asked.

"No," she said. "I'm afraid not."

Jackson excused her on the spot, without waiting for argument from the lawyers.

Many of the questions yesterday were more subtle. With the mayor for a defendant, no one expects to find a jury without preconceptions. The question for the judge and lawyers, in qualifying a panel to hear the case, is whether prospective jurors seem capable of setting aside their personal views and deciding the case solely on the evidence.

A young black woman whose name was not audible (the judge withheld the written list of panelists) made yesterday's cut despite a declaration, in early questioning, that she believes "the mayor is innocent" and her strongly expressed preference not to serve.

"I really don't feel that I can pass a judgment on someone, whether or not they're guilty or innocent," she said under examination by Assistant U.S. Attorney Judith E. Retchin. "I don't want to be put in that position."

R. Kenneth Mundy, the mayor's lawyer, would not let her go that easily. Jackson has allowed the lawyers considerable freedom to lead the witnesses, and when Mundy questioned the young woman, he skillfully salvaged her from dismissal.

"What you're saying is that like so many of us, you don't want to be in a position of passing judgment on your fellow man," he asked.

"Yes," she replied.

"But you understand that it's a part of your civic duty?" he asked.

"Yes," she replied.

Could she be impartial? Yes. Could she presume innocence? Yes. Would she refuse to convict if offered proof beyond a reasonable doubt? No.

Jackson qualified the woman without dissent.

Assistant U.S. Attorney Richard W. Roberts had no such luck with a young woman who told the judge she might have difficulty putting aside her beliefs: "I think he's guilty already."

Roberts tried three different ways to ask the woman whether she would obey the judge's instructions to set such opinions aside. On his fourth try, Jackson intervened. "Mr. Roberts, give it up," he said, as the galleries gave way to laughter. Jackson excused the juror.

Ten of the 17 jurors examined yesterday were ruled eligible to serve. In all, 94 have been examined; 58 have been qualified to hear evidence in the case. The initial phase of selection, aimed at screening out jurors with insuperable bias or urgent personal reasons not to serve, will end Friday. On Monday, Jackson said, the lawyers will make their final, so-called peremptory cuts, leaving 12 jurors and six alternates in the box.

The process has been slow and sometimes tedious, and spectators have stayed away in droves. Six rows of wooden benches reserved for the media -- accessible only by closely rationed passes -- were more than half empty by afternoon, and few curiosity-seekers took advantage of public seating.

"Crowd's thinning out," Barry observed, looking almost disappointed, as he returned from an afternoon recess.

For his own part, Barry remained in the courtroom all day, with campaign manager Anita Bonds at his right. Bonds, for whom the "voir dire," or jury selection, is tantamount to a highly specialized opinion poll, has said she is contributing her expertise in gauging the sentiments and leanings of the panel.

The job sometimes has been made murkier by the argot of law and lawyers. In the austere marble confines of Jackson's Courtroom 2, many of the prospective jurors are making their first bewildered acquaintance with legal English.

A D.C. schools employee, whose name was inaudible, had difficulty on the stand. Several of the questions on the 25-page questionnaire had eluded his best efforts, and he elected to leave them blank. Now, under questioning by Roberts, he sought translations of the winding, conditional sentences.

"Could you explain a little better for me, please?" he asked.

When Roberts got across that he wanted to hear the prospective juror's views on the fairness of the FBI sting at the Vista Hotel, the man replied, "Well, if he didn't know what was going on, then it was unfair."

"If I were to instruct you that even though you might think it was unfair it was nevertheless legal, and you have to consider that evidence . . . would you be able to follow that instruction?" Jackson asked.

"Yes, I would follow the instruction," the man replied.

Mary Guay, a white-haired woman in a cream-colored blazer, took a different view. "I have a feeling that my life is an open book," she said. "I wouldn't care {about surveillance}. If the law does want to catch somebody doing an evil, bad thing, then this is what they should do."

Etta Harris, who expressed "some reservations" about the government's conduct in the case, said "it just seemed underhanded to me." Asked whether she could use the videotaped evidence to return a verdict of guilty, Harris replied, "I'd have to follow my conscience."

A woman who said she was former director of crisis services at the Psychiatric Institute of Washington had other concerns. She told Mundy that "drug abuse is a medical disease that can be treated."

Retchin, the prosecutor, later asked her, "Does that mean that if the government's evidence shows beyond a reasonable doubt that Mr. Barry possessed cocaine, does that mean you could not return a verdict of guilty?"

"Even though substance abuse is a disease," the woman replied, "I still believe people are responsible for their own actions."

Retchin, who has spent 18 months investigating the mayor, let slip a small gap in her knowledge of his political universe. When Johnnie Mae Hardeman, another panelist, said she attended Mount Zion Baptist Church, Retchin asked whether her pastor, the Rev. Ernest Gibson, was a political supporter of the mayor. In fact, Gibson broke with the mayor and became a leading voice urging Del. Walter E. Fauntroy (D-D.C.) to enter the mayoral race.