THE SUPREME COURT has an unusual opportunity this fall. It can give four of its members a chance to put into writing things they have been saying about the decision that permits [or seems to permit] secret criminal trials.

That decision was so roundly denounced by the press and some lawyers when it was handed down in early July that no fewer than four justices have defended or attempted to explain it in public comments since. This is unusual in itself; justices almost never talk publicly about cases they have decided. But coming before the court this fall is another case that gives the justices an immediate opportunity to clarify officially a confused situation or -- better -- to rectify a mistake.

The new case involves a murder trial conducted in Hanover County, Va., just a year ago. The press and the public were excluded from the trial for reasons that are not entirely clear from the record. The closest the judge came to explaining why he permitted a secret trial was his statement that "having people in the courtroom is distracting to the jury." The state of Virginia now says the reason was that a juror in a prior trial had read a news account of the testimony.

During the second day of this trial, according to the judge's final order, the defendant's lawyer asked the judge to strike the prosecution's evidence "on grounds stated to the record." The judge granted the motion and acquitted the defendant.There was no further explanation of what had gone on in the courtroom, and the newspapers covering the trial could report the next day only that the defendant had been released.

The possibilities for mischief in situations like this are obvious. The evidence, the arguments for and against striking it, and the rationale of the judge's decision remain secret unless someone is prepared to buy from the court stenographer a transcript of the trial and wait days or weeks until it is prepared.

From what members of the Supreme Court have been saying about their decision last July, this does not seem to be what they had in mind. One justice has indicated that only pretrial hearings can be closed. There has been talk of transcripts or other ways of releasing information.But when this particular case reached the Virginia Supreme Court, the court approved this secrecy solely on the authority of the U.S. Supreme Court's recent decision.

If this were the only case of its kind, the justices might brush it aside. But in the first six weeks after the Supreme Court sanctioned some secrecy, courtroom doors were closed during trials in two states, pretrial hearings were closed in at least 11 states, as was one post-trial hearing. The reasons for secrecy have ranged from trying to shield potential jurors against prejudicial news to shielding a defendant against embarrassment.

While it is possible to square all these events with the interpretation the press has made of the court's July decision, it is not possible to square them with what the four justices have said. That's why the court should hear this case and reconsider the thinking that has allowed a veil of secrecy to descend on trial courts.