RARELY DOES the public get a glimpse of the

closed-door proceedings that determine the guilt or innocence of an accused person. No one can compel a jury to justify its decision. This traditional guarantee of privacy ensures each juror that he is free to make his own decision without fear of criticism or recrimination.

The fact that this tradition is so rarely breached, made it all the more fascinating to hear the testimony of five of the Hinckley jurors before a Senate Judiciary subcommittee. Sen. Arlen Specter (R- Pa.), the acting chairman and a former prosecutor, asked each juror if he or she wished to discuss the verdict. That five volunteered to do so was commendable. Their testimony provided the legislators with rare firsthand information on the pitfalls of the insanity defense as it is applied in the District of Columbia.

First, the jurors confirmed what we all suspected: the rule, with its shifting burden of proof and highly subjective judgments, is extremely difficult for the layman to understand and apply. The conflicting testimony of the psychiatrists seemed only to confuse the jurors further. The judge instructed the jury that not any kind of mental illness would excuse John Hinckley: in order to acquit they had to find that his illness prevented him from appreciating the wrongfulness of his act or from conforming his conduct to the requirements of the law. Apparently this distinction was not clear to the jury. One member testified that he voted to acquit because Hinckley has "some kind of a problem, (but was) not necessarily insane."

Next, it is clear that the burden of proof is a crucial factor. Because the prosecution bears the burden of proving sanity in these cases, a jury confused by the contradictory testimony of experts will give the defendant the benefit of the doubt. This is what the Hinckley jury did. This is also why many experts believe that an accused person who raises the insanity defense should bear the burden of proof himself. Congress is considering such a change in the law.

All five jurors expressed a preference for a "guilty but insane" option that would have enabled them to require treatment for John Hinckley without absolving him of moral responsibility for his act. And some expressed concern that the jury had not fully understood the possibility that the defendant could be freed after as little as 50 days unless the government were able to prove he was dangerous. Said one member of the panel, "I don't believe some jurors knew he had a chance of getting out if he could prove he would not harm himself or others. I had some doubt myself about what would really happen to him if he was found insane."

The subcommittee hearings will continue, but senators already have a formidable list of issues to consider in revising the insanity rule.