Since the assault on President Reagan in 1981 by John W. Hinckley Jr. - and the resulting verdict of not guilty by virtue of insanity - the United States has become polarized into two camps: The first wants to keep the insanity plea, although in modified form; the second to abolish it completely. In whichever direction, the public wants action.
If there is, however, a real desire to reevaluate the worth and fairness of this defense in US criminal justice proceedings, there is also a real need for clarification of the issue.
The insanity plea grows from a long tradition in Western law which calls for punishment of those who knowingly commit a crime but treatment for others who are not mentally capable of understanding the nature of their felony.
Of course, the rub comes in trying to determine mental capability. The legal community tends to defer to the expertise of psychiatric specialists. But the latter are loath to predict future behavior or to make judgments that may lead to legal determinations. Much of the public is distrustful of both. It sees lawyers misapplying psychiatric testimony to achieve their own ends - the innocence of their clients. And it believes that evaluation of mental health is imprecise and questions its admission as legal evidence.
Further, a fair reading of the insanity plea is extremely difficult when the issue is viewed under the glare of an assassination attempt, such as Hinckley's. The issue is also clouded when cast in partisan political terms, as merely hard-line vs. soft-line approaches to controlling crime.
Nor does media handling of this highly intricate and delicate question always result in public enlightenment. Recenty, for instance, public perception of the insanity-defense issue was likely confused by NBC-TV's powerful docu-drama ''The Burning Bed,'' in which a long-abused wife burned her husband to death and was then acquitted of murder on grounds of temporary insanity. Granted, the main focus of this teleplay was on wife abuse, spotlighting a victim's frustration when neither family nor public agencies came to her aid.
But was the point here that, under dire circumstances, homicide may be excused by insanity? The viewing audience was given to understand that this was a legal gimmick necessary to effect justice in a system not geared for this type of case. Among the sad reactions to the program was a day-after news report of a husband who set fire to his wife as a ''warning.''
CBS-TV addressed the insanity-defense issue as its main theme in another drama, ''With Intent to Kill,'' televised recently. This program drew a sympathetic picture of a young man who was accused of murdering his teen-age girlfriend but was ordered to a mental hospital after receiving a verdict of ''not guilty and temporarily insane.'' After treatment, he returns to his hometown to try to reconstruct what really happened. He is assaulted by angry locals, befriended by the victim's sister (who works as a newspaper reporter), and conspired against by the grieving father, who bitterly decries the insanity plea as a ruse criminals use to escape responsibilty for their actions. Ultimately, the father takes the law into his own hands, shoots the young man, and is put on trial.
How does the show end? You guessed it: Dad pleads temporary insanity.
These network productions may have been good dramas, but both badly distorted the issues surrounding the insanity-plea debate. They tended to reinforce the view that the plea is a legal device used to manipulate justice - sometimes with justification, often without.
Unfortunately, millions more viewers probably saw these prime-time, commerical-network shows than saw a thoughtful and multifaceted PBS discussion of the insanity defense in the series ''The Constitution: That Delicate Balance.''
Nonetheless, public opinion regarding the insanity plea is sharply divided. In the wake of the assassination attempt on President Reagan, a poll by the Associated Press and NBC News indicated that 87 percent of Americans thought that many murderers escape prison because of this legal defense; 70 percent wanted the plea stricken from the books.
In addition to the sentiment for dropping the defense altogether, there have been major moves toward modifying it. Most of these involve proposals to alter state laws by offering a ''guilty-but-mentally-ill'' defense, limiting sharply the circumstances under which a defendant's mental state may be considered in court, and placing the burden of proof on defense attorneys to show that the accused is insane, rather than requiring the prosecution to prove sanity.
Last month Congress - under prodding from the Reagan administration - disallowed the century-old insanity defense standard for federal crimes which allowed a defendant who proved he was unable to control himself enough to act within the law to plead mental incompetence. Now the insanity defense for federal crimes is limited to showing that a defendant could not ''appreciate the wrongfulness'' of a criminal act.
A related matter, the validity of psychiatric testimony, is also under debate. At issue are what questions such testimony should address and what weight the testimony should be given in court. Even professionals in this field are divided. For instance, the American Medical Association, which officially favors abolishing the insanity defense, would still allow juries to vote for acquittal if there was evidence that the accused was not aware, because of a mental defect, that he was committing a crime.
Loren Roth, president of the American Academy of Psychiatry and Law, believes psychiatrists should be allowed to testify in court. But he stresses that they are not qualified to make judgments on a defendant's competency to stand trial and should not be asked to make conclusions of law.
Actually, psychiatrists are now banned by law in federal court from drawing specific conclusions about sanity. But controversy still swirls around proposed limits on other expert psychiatric testimony.
Two University of California professors, William J. Winslade and Judith W. Ross, in their book ''The Insanity Plea,'' favor eliminating that defense and barring from the courtroom most psychiatric testimony about the defendant's state of mind. They would also separate the guilt and penalty phases of a trial if the defendant's state of mind was in question.
Herbert Fingarette, a philosopher who has written extensively on subjects of criminal responsibility and mental disabilities, would keep the plea but limit its use. ''It is essential to recognize that in our system of law, we condemn people who are responsible, but we treat as unfortunate those people who are unable to be responsible,'' Professor Fingarette writes.
This view seems to have the right mix of justice, compassion, and enlightenment. Perhaps someday it, too, will get prime-time TV exposure.