* Four Los Angeles police officers are captured on videotape beating Rodney King, and, when the case first comes to trial, a jury acquits the four officers of any wrongdoing.

* Lyle and Erik Menendez admit killing their parents with shotgun blasts, but juries deadlock, and both cases end in mistrials after the defendants claim that their parents sexually and psychologically abused them for years.

* Jack Kevorkian admits that he knew Michigan law prohibited assisted suicides when he put a mask over the face of a dying man and supplied him with carbon monoxide to help end his life. A jury finds Dr. Kevorkian not guilty of assisting in the suicide.

Such verdicts raise the question: What's going on in courthouses these days that is prompting 12 people selected for their common sense to make such decisions?

It has become an American sport to second-guess juries. Most second-guessing goes on in cases that attract a lot of publicity, where the second-guessers haven't heard all the testimony but base their assumptions of justice on what they learned in a 30-second television broadcast or some newspaper articles about the case.

L Those who work with juries say they generally do a good job.

"The thing that amazes me is how hard juries try," said Baltimore County Circuit Court Judge Dana M. Levitz, a former deputy state's attorney who teaches trial advocacy at the University of Baltimore Law School.

Outright jury nullification -- such as in the Kevorkian case, where jurors ignore the law and vote their instincts -- is extremely rare, legal experts say.

"It's only going to happen in a case where there's a lot of emotion and people have strong feelings about what the law should be," said Ron Kuby, a prominent New York civil rights lawyer. "As a general rule, it's not a good thing."

Juries are the wild card in the legal system, the unpredictable element.

What goes into their decision can be extremely complex -- depending not just on the evidence, law and trial tactics, but on the bonds that develop among jurors and the personalities, backgrounds and beliefs they bring into the jury room.

No lawyer, legal expert or psychologist can predict the effect a photo of a bloodied corpse will have on a jury or say whether a jurors will sympa- thize with a plaintiff who cries on the stand because a car accident cost him a leg.

But a juror's life experiences often turn out to be a key. In the Kevorkian case, the jury panel included five people who worked in medical-related jobs. One of them, Gail Donaldson, a 42-year-old visiting nurse, said that testimony in the trial brought back memories of her terminally ill sister and father.

"I don't think it's our obligation to choose for someone else how much pain and suffering that they can go through," she later told reporters.

Most of the jurors initially voted to convict Dr. Kevorkian but reversed themselves in nine hours of discussion that included some tears and a lot of prayer.

"I do believe an individual has a right to decide what happens to their own lives and bodies and not the government or the legislature," Gwen Bryson, another juror, told the Washington Post.

The jury system means taking complicated issues in fields such as law, medicine and finance and putting them in the hands of office workers and secretaries, salesmen and truck drivers.

And there is nothing wrong with that.

"Jurors are generally studious. They want to do the right thing and listen to all the evidence. But overall, common sense prevails over any law, in my opinion," said Richard M. Karceski, a criminal defense lawyer in Towson.

And like many other things, jury selection has become more complicated.

Dr. Kevorkian used three jury consultants, private firms that offer advice on how to pick jurors, to select his jury. Rates for such services can run up to $200 an hour.

"We were looking for were people who had relatives or people they had worked with who had been sick or terminally ill," said Paul Tieger, whose firm, Communication Consultants in West Hartford, Conn., was one of the three firms that worked for free on the Kevorkian case.

A 12-page questionnaire was distributed to potential jurors before the Kevorkian trial probing their attitudes about mercy killing, abortion and their religious beliefs and values, Mr. Tieger said.

Elissa Krauss, a consultant with the National Jury Project, a Philadelphia jury consulting firm, said jurors will often respond better to intimate questions when asked to give their answers in writing.

Ms. Krauss helped Baltimore lawyer M. Cristina Gutierrez select the Anne Arundel Circuit Court jury that acquitted Northeast High school teacher Laurie Cook of child abuse charges.

"If it's a case of child abuse, it's very important to know what a juror's experience has been in that area," she said.

Jury consultants are not used in most cases; most lawyers still go with their instincts when picking a jury. "It's a gut feeling. A lot of us like to look the person in the eye and if the person looks you back, that's a good sign," Mr. Karceski said.

Lawyers say that even with experts, it is impossible to predict and difficult to say what happens in one person's decision-making process, let alone how 12 people will decide.

One juror may be persuaded by a lawyer's closing argument, another may be turned off by an arrogant witness and a third may lack sympathy for the victim and develop an emotional tie to a defendant.

"It's as complex as the people are," said Ms. Krauss.

If the lawyers are effective, every exhibit, every witness and every word spoken in court is brought before a jury for a reason. A prosecutor in a murder trial will usually make sure jurors see a victim's bloodied corpse to convey the stark reality of the crime. Implicit in such evidence is the message that somebody ought to pay for the brutal death of this housewife, this doctor, this ditch-digger.

But sometimes, jurors will end up deciding cases partly on factors that are totally unanticipated by either side.

In 1981, a group of parents filed a $17 million federal suit against the Anne Arundel County school system, alleging that their children had been mistreated in an Annapolis elementary school because they were put in storage rooms as punishment for being disruptive.

The case dragged on for more than two years; when it finally came to trial, it ended with a deadlocked jury and declaration of a mistrial.

One juror later said that she listened carefully to the complicated arguments for both sides but that her decision was partly based on her belief that the school's lawyer was telling the truth. She believed him, she said, because of whom he brought to mind whenever he got up to speak:

"He reminded me of my father."

C7 Dennis O'Brien is a reporter for The Baltimore Sun.