A FEW WEEKS ago I sat on a jury and helped acquit a man I believed to be a drug dealer. How could that happen? My first experience as a juror left me disturbed. Did I fail the system -- or did the system fail me?

Our jury was impaneled the same day as Marion Barry's. The charge involved possession of crack cocaine. But there the resemblance between the two cases stops. There were no media present, no lines of spectators. The trial lasted barely two days. It was just a routine day at Superior Court.

During voir dire, potential jurors who knew the defendant or the witnesses were excused, as were those with close ties to law enforcement officials, those affected by drug-related crime or charged with any crime in the past five years, and those whose experience with drugs or alcohol might affect their impartiality. About one-third of the courtroom cleared out.

From the remaining body of prospective jurors, the attorneys for both sides exercised their peremptory challenges until they wound up with 14 people, including two alternates. Eleven jurors were women; five were black. The final cut brought the jury to eight white women, an Asian-American woman, a black woman and two black men. Not only were we hardly representative of the District's demographics; we were not at all so of the defendant's world.

The defendant was a young black male, charged with possession of cocaine and intent to distribute. Police witnesses testified that they had spotted him with a medicine bottle in his hand at a crowded open air drug market in Northeast Washington. When the police car arrived everyone scattered, including the defendant who allegedly left the bottle containing 72 rocks of cocaine behind a wall. The officers, who knew the neighborhood well, recognized the young man. They arrested him a few days later.

It seemed an open-and-shut case, and I wondered why it hadn't been plea-bargained away. The defendant who without a steady job, was obviously being represented by a first-class attorney. How, I also wondered, could he afford such apparently high-priced talent?

His lawyer quickly picked up inconsistencies in the two police officers' testimony. They differed on whether the squad car was marked or unmarked, where it was parked, what clothes the defendant was wearing, the number of people present, and whether they had a clear view of the events. It did not seem odd at first that their memories about an alleged crime committed in September 1988 might be shady, until it was revealed the officers had held a pre-trial conference to refresh themselves.

Defense witnesses also gave accounts which differed from one another and, naturally, from those of the police. The only solid testimony seemed to come from a witness who gave the jury a crash course on how illegal drugs are dealt. By this time my initial notion of the defendant's guilt had been superseded by doubts and confusion. After hearing the witnesses and being told by the presiding judge to rely on my memory -- an exceeding difficult task for a reporter used to the security of pad and pencil or tape recorder -- I was counting on the attorneys' summations to lay out the facts of what had really happened.

As the opposing counselors played to the jury, the mismatch between them became obvious. A young, unflamboyant prosecutor was up against an experienced and demonstrative defense counselor. The younger lawyer asked the jury to use its "common sense," while the other, dismissing any appeal for sympathy on behalf of his client, implored the jury to "weigh the facts." By this time, I was mentally picking daisies, saying "He's guilty; he's not guilty; he's guilty."

Finally the judge instructed us on how to deliberate. Two points stuck in my mind: The policemen's testimony should not be afforded more credibility just because they represented law enforcement, and "beyond a reasonable doubt" meant that if I was not sure the government had proved its case, the verdict should be not guilty.

Once inside the jury room, the initial tally showed one vote for guilty, six votes for not-guilty and five (including mine) for undecided. Then the white women who had been talking politely to each other about trivia for the past day on judge's orders, exploded. Why were there so many discrepancies in the police account? Why didn't they fingerprint the bottle? And so on. The two black men kept their opinions to themselves, but went along with the majority opinion.

Second vote: 11 not guilty, one undecided. Lingering doubts. Were we overly influenced by the performance of the defense attorney? Finally, after 45 minutes, it was all over. Before we left the jury room, we took a final show of hands in an informal inter-jury poll. Of course, we had not been informed whether or not the defendant had a prior criminal record. About half the jurors, including myself, believed the defendant was actually guilty of the crime, although the government had not proved its case within a reasonable doubt. We felt we had no choice but to render a verdict of not guilty.

After the jurors were dismissed, several met with the attorneys in the corridors for a casual post-mortem. The defense attorney, James W. Robertson, said his successful strategy on jury selection had been to pick as intelligent a jury as possible. "I was looking for college graduates," he said. Robertson, a Howard University law professor, has been defending criminals since 1976. He was co-counsel last year at the Rayful Edmond III's trial.

The prosecutor engaged in a separate off-the-cuff discussion on the courthouse steps with a few jurors to find out what happened. Though he later declined to repeat his comments on the record, his casual observations offered some insight into the seeming paradox we had just experienced.

Since most aspects of life in the District seemed to be affected to some degree by race, it was no surprise that the racial composition of the jury was an important factor.

Asked about the jury selection, the prosecutor responded that counsel for the defense "kept knocking off blacks" to get a group composed mainly of white women. The prosecutor indicated that history had shown there was a predictable outcome from a predominately white female jury when the defendant was a young black male. The women invariably go out of their way to avoid appearing racist. Since they are not familiar with the drug scene, they tend to intellectualize, to judge on the basis of cold facts, rather than hot emotions. Black women, on the other hand, tend to be more personally affected by drugs and are therefore more apt to want to rid a neighborhood of drug dealers by convicting them.

Defense attorney Robertson said in a subsequent interview that the prosecutor had complained to a third attorney that his defeat was due to the presence of a "white liberal" on the jury.

The prosecutor asked if the jurors believed the police officers' testimony. When reminded that there were a disturbing number of discrepancies, he responded by noting that the police have many cases of this type and that this was a typical presentation of evidence. He saw no need to put two additional police officers on the stand.

He labeled the defense's call for fingerprinting of the suspect bottle a non-issue. A friend of the defendant had testified that another young man, who was killed three days later, had actually stashed the drugs. The prosecutor accused the jurors of falling for the old trick of blaming the crime on a dead man.

The prosecutor recalled that until a few years ago, jury duty lasted two weeks, not one day or one trial, as under the current system. Implying that the women were naive about the real world, he told them that if they had to sit through several drug trials, they would soon learn some street smarts. They would learn to recognize the familiar line proffered by drug dealers.

But is it my civic duty to learn about street crime to be a juror in the District of Columbia? Did I fail the system?

Or did the system fail me? Did the makeup of the jury and the slipshod testimony make a not-guilty verdict inevitable? Will our acquittal come back to haunt us?

Immediately after the trial, another juror remarked, "I just hope I don't see {the defendant's} name in the paper next week being arrested on drug charges." That's my hope, too.

Nancy L. Ross is a Washington Post reporter.