There's been a lot of sneering behind hands about the jury that found John W. Hinckley Jr. not guilty by reason of insanity.

Some say it should have been expected. After all, they note, the jury was nearly all-black, most blacks dislike Reagan and therefore the jury probably was looking for some way to let the would-be assassin off. Why, others ask, should a group of blue-collar blacks be expected to turn on a rich young white boy for shooting a right-wing president. You may have heard some of this talk yourself. I have. Even some blacks have been complaining of the ridiculous behavior by the jury.

Some of this bad-mouthing is understandable. This has been an emotional verdict, and the jury is a convenient scapegoat. But it's all out of order. The verdict and the stormy controversy surrounding the insanity law really demonstrate a profound truism: black people are probably more law and order oriented than any other group in society. Even though there is enormous variety among blacks here, your average juror is a solid citizen who goes to church on Sunday and obeys the letter of the law perhaps more than any other group.

Still, every time there is a sensational trial here, Washington juries become a topic of discussion.

In 1974, when the Watergate grand jury named Richard M. Nixon as an unindicted coconspirator, then-White House aide Patrick J. Buchanan wrote:

"Only a single member of that 23-member grand jury was a Republican. Seventeen of the 23 were black--members of a racial minority that voted, nationally, upwards of 10 to 1 against the president, a minority whose political leaders have repeatedly characterized Richard Nixon and his administration as bigoted and racist."

And William Safire sniggered quite regularly that no white person could get a fair trial in Washington.

The same charge was echoed the following year when the Watergate defenders said they didn't believe that they could get a fair trial in the District because most jurors are Democrats and black. But in case after case, all of these people were proved wrong.

Black jurors have shown sophistication. Former White House aide John D. Ehrlichman, while on trial for his role in the break-in at the offices of Daniel Ellsberg's psychiatrist, had a black lawyer on his defense team--an obvious attempt to win favor with the predominantly black jury. Ehrlichman was convicted anyway.

The trials of Rep. Charles Diggs and Joseph P. Yeldell and millionaire developer Dominic F. Antonelli Jr. raised yet another question about justice here. Diggs and Yeldell were powerful black leaders. Diggs brought in Coretta Scott King, Jesse Jackson and Andrew Young as character witnesses. Antonelli's lawyer waved a Bible during closing arguments. A jury of 11 blacks and one white convicted Diggs, at the time the senior black member of Congress; 12 blacks convicted Yeldell. Indeed, after the judge threw out the Yeldell verdict, both men were acquitted in a retrial in Philadelphia before a mostly white jury.

The Hinckley jury was in this same tradition. Even though some of the jurors have since expressed misgivings about their verdict, their frustration was with the system that essentially gave them only two choices--guilty or not guilty by reason of insanity. They would have preferred to find him guilty but insane.

The Hinckley verdict was an incredibly courageous one. The jurors must have known they would face a lot of abuse. They must have known that some would blame them rather than the law.

The verdict in the Hinckley trial proves again that a Washington jury can make its way through a sophisticated case. John Hinckley walked because of the quirks in the law, because Judge Barrington Parker charged the jury to find Hinckley not guilty unless the prosecution proved his sanity beyond a reasonable doubt, and because Hinckley's folks had enough money to mount a $1 million defense.

All of these Washington juries, all of the plain folks handling complicated and highly publicized cases, send out the same message: No matter who you are, you'll get as fair a trial in a courtroom here as anywhere else.