The arduous task of selecting the 12 jurors and six alternates who will decide the fate of D.C. Mayor Marion Barry began yesterday in federal court, as 250 District residents filled out questionnaires asking them to reveal such things as their experiences with alcoholism and racial prejudice.

The 25-page questionnaire, fashioned by U.S. District Judge Thomas Penfield Jackson, asked such questions as:

"Have you, or has a relative or any close friend, ever been addicted to any drug?" Also: "Do you have any opinion as to whether a person is ever justified in lying after having taken an oath to tell the truth?"

Divided into two groups of 125 each, the prospective jurors spent the day on the questionnaires, which also covered such controversial topics as whether juries are ever entitled to ignore the law, how often they go to church and whether they had attended any Barry fund-raisers since Jan. 18, the date of his arrest on cocaine charges at the Vista Hotel.

The detailed questionnaire -- and the size of the jury pool -- indicated the high-profile nature of the Barry case, as well as the enormous latitude federal judges are given in voir dire, as the process of jury selection is called. The questions were designed to elicit information that either side might need to identify those who harbor bias.

For instance, prospective jurors' responses to questions on alcohol and drug abuse might be reason for the prosecution or defense to ask that they be excused for cause. Prosecutors might want to excuse someone who is a former drug addict; the defense might want to excuse one embittered by a former spouse's alcoholism.

The questionnaire also asked how much prospective jurors' opinions of the case may have been formed by the publicity surrounding it, whether they knew anyone on a list of 48 potential witnesses, and if they had ever been a contractor for the D.C. government.

The 250 people also faced questions about their political beliefs: whether they voted in national and local elections as far back as 1978, what party they were registered to vote in, whether they are active in local politics.

The questions also sought to lay bare private attitudes about legal issues that are expected to form the crux of the Barry defense, such as the prospective jurors' opinions on undercover "sting" operations, whether the Barry prosecution was a political vendetta, and jury nullification, a legal strategy in which the defense seeks acquittal based on jurors' dissatisfaction with the government.

"If, during the course of jury deliberations, a fellow juror should suggest that you disregard the law or the evidence, and decide the case on other grounds, would you . . . be able to reject the suggestion and abide by your oath to this court to decide the case solely on the evidence and the law as the court has instructed you, without regard to sympathy, bias or prejudice?" it asked.

In an interview with The Washington Post last week, Barry himself referred to that possibility.

"I think the prosecutors know that in this town, all it takes is one juror saying, 'I'm not going to convict Marion Barry. I don't care what you say,' " he said. The mayor also has stated that prosecutors made an unprecedented effort to entice him into breaking the law. That apparently prompted a question about attitudes toward sting operations.

"Do you hold any personal opinions about the use of undercover . . . operations in which, for example, friends or associates of a subject cooperate in monitoring the subject's activities?" prospective jurors were asked. The next question asked whether they had opinions about "the fairness of using concealed video and audio recording devices" during a sting.

To find out how much the respondents had been swayed by Barry's statements of contrition and religious conviction since he returned to Washington after a seven-week course of treatment for alcoholism, they were asked: "Would a defendant's religious beliefs, or the fact that a defendant had asked for Divine forgiveness, affect your judgment upon his innocence or guilt of a criminal charge in any way?"

The questions also delved directly into the issue of race.

"Do you have an opinion as to whether race or politics played any part in the charges against Mr. Barry?" asked one question. The next said, "Have you ever believed yourself to be a victim of prejudice of any sort?"

Those who feel constrained about answering some questions in public can put in a request to speak to Jackson and lawyers in the case in private, though it was not clear how many such requests will be honored.