Still appearing frightened and reclusive, clearly burdened by his role as a symbol, Rodney G. King has had only a few stumbling words to say in public since he was beaten by the police two years ago. And in private, talking about the beating to investigators, he has sometimes contradicted himself.

Now, in the prosecution's biggest gamble, he is expected as early as Tuesday to testify for the first time against the four officers accused of violating his civil rights.

His testimony could change the course of the trial, but nobody knows just what he will say. Innocent victim or aggressive felon, the man the jurors see on the stand could influence the way they view the videotaped beating.

Mr. King's pain and bewilderment were evident in his emotional statement at the height of the riots last May 1. "People," he began, "I just want to say, can we all get along? Can we get along?" And he concluded: "We've just got to, just got to. We're all stuck here for a while. Let's try to work it out. Let's try to work it out." No Stranger to Trouble

But more frequently, the 27-year-old unemployed construction worker has been seen here in police custody, once accused of drunken driving, once accused of beating his wife and once for driving his car at an undercover officer after being surprised with a transvestite prostitute. No charges were filed in any of the cases.

In a state trial of the four officers last year, prosecutors chose to avoid the risks of bringing Mr. King to the witness stand and trusted instead in the power of the videotape that shows him being beaten and kicked for 81 seconds.

This gap in their presentation left the way open for defense lawyers to portray Mr. King as "an animal," a dangerous, almost superhumanly strong felon, sweating, grunting, violent and impervious to pain.

Sgt. Stacey C. Koon, Officers Laurence M. Powell and Theodore J. Briseno and former Officer Timothy E. Wind were acquitted of assualt charges last April 29, touching off days of rioting. They now face possible 10-year prison terms on civil rights charges that they used excessive force when they arrested Mr. King for speeding. 'Real Human Beings'

"The jurors had the defendants as real human beings to identify with and sympathize with but no human being on the prosecution side of the case," said Erwin Chemerinsky, a law professor at the University of Southern California. "Rodney King could provide that."

But Mr. King does have a criminal record, for armed robbery, and his actions on March 3, 1991, did contribute to the events that followed, all elements that defense lawyers are likely to focus on. One of them said today he expects Mr. King to undergo cross-examination for at least a full day.

Aware of the risks, the prosecutors have gone out of their way to play down Mr. King's testimony, sandwiching his appearance between those of expert witnesses and acknowledging his problems to the jury from the start.

"He will tell you that he was on parole and that he broke the law on the night of the incident," said a prosecutor, Steven D. Clymer, in his opening statement Feb. 25. "He was drunk while driving, and he was speeding as he tried to get away from the police.When they tried to handcuff him, he resisted." 'A Very Poor Memory'

Furthermore, said Mr. Clymer, an assistant United States attorney, "I expect Rodney King will tell you that because of the beating he has a very poor memory of the incident. He has made several statements that are inconsistent, with different versions of the events."

But he emphasized: "Rodney King is not on trial. The issue of whether he was guilty or innocent that night is not the issue in this trial."

These statements are part of a prosecution tactic, said Peter Arenella, a law professor at the University of California, Los Angeles.

"A basic message the prosecution wants to send to the jury is that they do not have to choose between King and the officers as to who is ultimately more sympathetic and appealing," he said. "They are going to do their best to educate the jury that even a criminal who is clearly resisting lawful authority retains the constitutional right to be free from excessive force."