WHAT'S GOING ON down there in Quantico? Three days into the espionage trial of Marine Sgt. Clayton Lonetree, there is little information about what is happening inside the courtroom, but plenty of hoopla on the outside. William Kunstler, a veteran of the war protest trials of the 1960s, is playing his familiar role of outraged defense attorney, charging the prosecutors and the military court with everything from bad faith to complicity in a plot to avenge Gen. Custer. Sgt. Lonetree's family, who are American Indians, say that the prosecution is yet another example of racist injustice, and they have used the symbols and ceremonies of their heritage to demonstrate support for the accused. All this is fascinating, but tells little about the merits of the case.

The American public wants to know all the facts about the case of the embassy guards. But the American public knows very little about the military justice system. Most of the proceedings of the first three days were conducted in secret. This reinforces the perception that various aspects of the case have been fouled up from the start and that the prosecutors have a weak, and perhaps trumped-up, case. It also makes people wonder whether the military justice system is basically unfair. Neither allegation may be true, but the government must go out of its way to explain, to be fair to the accused and to justify any procedures that are at odds with practices in civilian courts.

Set aside charges of race prejudice; we have seen no evidence that Sgt. Lonetree, who voluntarily turned himself in to U.S. Embassy officials in Vienna, has been singled out for prosecution because he is an Indian. But the charges against him must be proved in open court if the public is to have confidence that he has been treated fairly. There can be no secret witnesses whose identity is not revealed to the defense. There should be no reluctance to supply the defense team with documents as innocuous as training manuals. And there should be no punitive detention. Sgt. Lonetree's attorneys claim he has been kept in solitary confinement for eight months, and that only in recent weeks has he been allowed to exercise without shackles.

This trial involves national security, but it has also raised questions about the quality of military investigations and the civil liberties of military personnel who are charged with serious crimes. The proceedings should be opened to the fullest extent possible. The accused must be granted every opportunity to present his defense and to be treated as innocent until he is proved guilty. And the prosecutors should take every opportunity to explain what is going on and why each step is both necessary and fair.