The pretrial motions are nearly over. The evidence has been amassed, arranged, numbered. The lawyers have prepared their strategies. Just about every American by now has heard the basic, stunning details of the case. But there is at least one major mystery left: Which 12 people will decide if O.J. Simpson is a murderer?

Lawyers believe that before a single witness is cross-examined in court, before a single exhibit is put into evidence, a trial can be won or lost. Thus when Simpson goes to trial today, the first step, selecting a jury, is likely to be excruciatingly tedious.

It might take a month. Judge Lance A. Ito will not allow cameras or microphones in the courtroom while the jury is chosen. The defense attorneys have given the judge a list of questions they want asked of every potential juror. The list is 50 pages long. The prosecutors are even more inquisitive: They have 100 pages of questions. There are 1,000 people summoned to the court as potential jurors.

Ito will combine the two lists and throw out the redundancies. The lawyers and their specially trained jury consultants will not just analyze the answers -- they will listen to the subtleties of tone, watch the hands, track the eyes.

In courthouses throughout the country, jury consultants are proliferating madly. A few decades ago, they did not exist. Now there are hundreds of them nationally, pulling in $200 million a year as an industry. Some legal scholars condemn the trend. They say jury consultants are rigging the game. Juries are supposed to be representative of the community, not handpicked for pliability. Courts occasionally remind lawyers that their mission in jury selection is to find people who are fair and impartial -- period.

That makes lawyers laugh. Slays them.

"If there has ever been nonsense, that's it," says Albert Krieger, a Miami defense attorney who has represented mobster John Gotti. "Prosecution wants convicting jurors, and defense wants acquitting jurors."

Both sides have hired outside jury experts. The prosecutors retained a firm called DecisionQuest. The defense employed a consultant from Trial Logistics Inc. and is considering using graphics from an Annapolis-based company, Forensic Technologies International. The barristers have taken jury selection into the Space Age.

The case may turn on how the jurors feel about circumstantial evidence. There are apparently no witnesses to the June 12 murders of Nicole Brown Simpson and Ronald L. Goldman. The prosecution will have to assemble its case in tiny increments, bloodstain by bloodstain.

The state believes all the evidence points to the great Hall of Fame running back, rental car spokesman and actor. There's a DNA match of Simpson's blood at the murder scene. A bloody glove in Simpson's back yard matched one found near the bodies. There was a history of violence in the Simpson marriage. Simpson bought a stiletto shortly before the murders. No other plausible suspect has been identified. The Los Angeles district attorney, Gil Garcetti, has characterized it as an open-and-shut case.

Trial experts disagree. They think Garcetti will lose. Indeed, criminal defense lawyers and trial consultants seem to be almost unanimous in thinking that Simpson probably cannot be convicted by a "downtown jury," that the trial will end in either a hung jury or outright acquittal.

When attorneys in Los Angeles talk about a "downtown jury," they mean a jury with a heavy representation of African Americans, Latinos, Asian Americans and blue-collar workers. The jury pool is drawn from a 20-mile radius from the courthouse.

"The D.A. will not be able to convict him," says Barry Tarlow, a nationally prominent defense attorney based in Los Angeles. "Garcetti shot himself in the foot as usual. This case could have been tried in Santa Monica. A Santa Monica jury would have been much more receptive to what the D.A. is selling."

"I see at best a hung jury," says Leo Terrell, a civil rights attorney in Los Angeles. "You've got a circumstantial case. You've got no percipient witness. You've got no murder weapon. Those things are very important for a jury of 12 to unanimously conclude that O.J. Simpson was guilty of two murders. I think that's going to be a tough call for the jurors."

The race of a potential juror is not what is most significant, say the trial experts. Rather, it's the attitude toward law enforcement. Many African Americans have a skeptical view of police officers and may be receptive to defense arguments that the police were out to get Simpson. No one in Los Angeles has forgotten Rodney King.

"Of course, you'll want people of color," says Terrell, speaking of the defense team's strategy. "African Americans feel the criminal justice system has been unfair to them."

Beth Bonora, a trial consultant with a private firm called National Jury Project West, says she has been asked many times by reporters about the supposed bias of African Americans in favor of Simpson. That is utterly backward, she says. "In general, the African American population is somewhat more likely to presume innocence. Which is what everyone is supposed to do."

The Familiarity Factor

Simpson has another advantage: The jurors will know him. They will have seen him on television for two decades. Many will remember him as the local football hero, when he won the Heisman Trophy at the University of Southern California. It is exceedingly rare that jurors ever sit in judgment on someone they know, someone they have admired, someone whose pain touches them directly. When they deliberate, they will feel the immensity of their burden -- this isn't just any 47-year-old man whose fate they are deciding, this is O.J.

Legal journalist Stephen J. Adler says the procedure is not fair. His new book, "The Jury: Disorder in the American Courts," says lawyers try to seat jurors who are easily swayed or confused. That is one reason there has been a profusion of bizarre verdicts in high-profile cases, such as the $10.5 billion jury award against Texaco in 1986 when -- according to Adler's book -- jurors explained that they had added a billion dollars in damages for each Texaco witness they had despised.

Each side in the Simpson case has 20 peremptory challenges, in which they can remove a juror without citing a reason. The Supreme Court has outlawed peremptory strikes on the grounds of race and sex, but they still happen, disguised as some other objection of the juror.

The system in which a panel of ordinary citizens makes the most sensitive decisions of justice has roots stretching back to medieval England, virtually to the Magna Carta. The English novelist G.K. Chesterton wrote that civilization had decided that the determination of guilt or innocence was "too important to be trusted to trained men."

But Britain in recent years has largely abandoned the jury trial. That leaves the United States as one of the few places on the planet that puts so much power in the hands of common people. In this country, the jury has achieved a mythic status, never more grandly advanced than in the movie "Twelve Angry Men," where maverick juror Henry Fonda's courage and reason saves an innocent man from execution. In literature, juries have fared less well. In Robert Penn Warren's "World Enough and Time," the narrator tells of a hung jury that settled the issue with a card game called Old Sledge:

"On the stroke of midnight, the score was seven to seven, when the hanging champion threw the jack and won the game. So the gallows was built and on it was nailed the Jack of Spades."

The game is more sophisticated now. Juries are put together as carefully as nuclear submarines. Big companies, rich defendants and nervous prosecutors take no chances. National Jury Project West has received as much as a half-million dollars consulting on a single jury trial.

Roy Black, hired by William Kennedy Smith in the alleged rape of a woman at the Kennedy estate in Palm Beach, Fla., initially assumed that young men would make the best jurors for Smith. Black figured wrong. He and his consultants, including Robert Hirschhorn of Galveston, Tex., conducted focus groups and found that young men would be the worst jurors for Smith. The best: Older women.

Black made sure there were no young men on the jury. There were several older women. Smith was acquitted.

Explains Hirschhorn, "Older women were the best possible jurors for us, because they couldn't understand why in the world at 3 o'clock in the morning a woman would be driving a guy to his house and taking her pantyhose off unless she had sex on her mind."

Race, sex, age, religion, national origin: These are only the obvious, superficial characteristics that come into play. There are more important factors inside the skull. Each side will want to know how a person thinks. It is probably the hardest thing to tease out during the questioning of prospective jurors.

The prosecution will want people who think in broad terms, who will be impressed by the array of physical evidence and prepared to reach a consensus. The defense will want mavericks who make up their own mind, everyone else be damned. The defense will want people who demand that every piece of information fit together seamlessly, who'll be disturbed by missing elements -- the kind of people who compulsively dot their i's and cross their t's.

The prosecution will argue that DNA tests are consistent with Simpson's being the killer. The defense will point out that, even if the state experts could be trusted, the blood would still only be "consistent" with Simpson's. That implies some degree of doubt. There is a possibility that the blood could have come from one of many other unknown persons. The defense will want jurors who zoom in on the uncertainty.

Gauging Reasonable Doubt

Jury consultant Hirschhorn says one question he would ask during jury selection is whether a person would be unsatisfied if upon balancing a checkbook, there was still a $5 discrepancy.

"The kind of juror I would want for O.J. is the juror who would not think the checkbook was balanced until he found that five dollars. Because that five dollars is the reasonable doubt," Hirschhorn says.

The prosecution must contend with a few perplexing details. If Simpson committed the crime, he did so with amazing speed, on the run, fitting it between a trip to McDonald's and a trip to the airport. The defense will say the window of opportunity was too small. Simpson's lawyers will argue that police botched the investigation, forgot to call the coroner for 10 hours, and let a novice handle the blood and mislabel some of it.

The prosecutor's office won't want jurors who tend to fidget with loose ends.

"If they're analytical, where they have to have everything in place, everything in order, everything add up, and nothing missing, then the prosecution would lose," says Julia Cade, an Alexandria trial consultant.

Jury consultants watch to see whether the prospective juror shifts in the chair, smiles, fidgets, looks toward the other side's attorney. A juror who comes to the courthouse in formal clothes and says "Yes, sir" and "No, ma'am" is likely to be more "authoritarian," a good prosecution juror. There are all kinds of nuances to the old rules of Clarence Darrow, who in 1936 advised defense attorneys to avoid Presbyterians, Scandinavians, Christian Scientists and the very rich.

Lawyers and their consultants rush to say that they don't rely on stereotypes. The evidence is what really matters, they say. Jury-selection-by-microscope notwithstanding, juries get the verdict right, they argue.

But Terrell, the Los Angeles civil rights lawyer, says, "If we are to assume that the case will be decided solely on the evidence that's presented, then we're living in a theoretical world. ... It's the way you dress. It's what you look like. It's your racial composition. It's how you present the evidence. People get caught up in all these wrong factors. You have to acknowledge that these factors exist."

The Simpson prosecution team used a focus group in Phoenix to get clues to how its case would fare with jurors. The "trial" was crammed into a few hours. The faux jurors voted for acquittal. Among other things, they felt that lead prosecutor Marcia Clark was too aggressive.

The use of outside jury consultants may have paid off earlier this year for celebrity defendants Lyle and Erik Menendez, young men from a wealthy Beverly Hills family. In August 1989, the Menendez brothers went to San Diego and used false identification to buy shotguns and ammunition. Back in Beverly Hills, they burst into the house and slew their parents. The father was shot in the back of the head, the mother in the face. The brothers dumped their bloody clothes, hid the weapons and went to a movie.

Erik Menendez eventually confessed to a therapist. The following March, they were arrested. The district attorney wanted the death penalty. Lois Heaney of National Jury Project West was retained by the defense.

What no one knew until jury selection began was that the brothers intended to admit they shot their parents and claim that it was a preemptive strike in self-defense. They said they had been sexually abused by their father. They said they thought their father planned to kill them to protect the secret. Heaney and the defense team had to screen out any jurors who couldn't buy that kind of defense.

The defense team prepared 122 questions. Each juror had to answer in writing. The jurors were asked, "Do you have any strongly held beliefs that a child does not have the right to kill a parent in self-defense?"

And: "What sort of psychological effects do you think continuous physical, emotional, psychological or sexual abuse by a parent toward a child has on the child?"

The brothers were tried together but with two separate juries. Both juries were hung. Roughly half in each case wanted a murder conviction and the rest wanted to convict only for manslaughter. The brothers will be retried, again for first-degree murder.

It is important to remember that no matter what the two sides are looking for in a juror, human beings are still unpredictable. The lawyers might think that a football fan, for example, will sympathize with Simpson, but they can't know for sure. Even if all the factors could be put into a computer, the juror might still vote contrarily.

When Rodney King sued the city of Los Angeles, the forewoman of the jury, a Filipino American, turned out to have been the wife of a deceased Black Panther who had been the victim of FBI harassment. Had the lawyers for the city known that, they would never have wanted her on the jury. Presumably, she would have been biased in favor of Rodney King. As it turned out, she was the juror who forged the compromise that gave King several million dollars in compensatory damages but not a dime in punitive damages.

Jury selection, says Terrell, "is a crapshoot."

The Simpson trial will be televised nationally and will probably rivet the nation, particularly if and when Simpson testifies in his own defense. But no one will see the deliberations. The jury will judge Simpson in private. Twelve people will bear a historic responsibility of weighing the evidence against the most celebrated murder defendant in the annals of American jurisprudence.

In the past, juries have often locked onto strange little details as being the pivotal fact of a case. There is always a temptation to play Sherlock Holmes.

There is a story in the federal legal guide "Courtroom Communication and Jury Selection" about a jury that had to decide how much money a woman should get in a liability case. She had injured her back when a car struck her from behind. In the jury room, the jurors talked about her toes.

During the trial, her toenails had changed color.

The jurors decided she did not deserve much -- because how badly could her back be injured if she could bend down to paint her toes?