The trial of John W. Hinckley Jr. for attempting to assassinate President Reagan is bringing a long-simmering controversy to a boil. At issue: the insanity plea, and its premise that a person cannot be judged guilty of a crime if because of mental illness he couldn't distinguish between right and wrong or didn't have the capacity to conform his actions to the law.
This premise is under increasing fire from citizen groups coalescing around the law and order issue. Their concerns are being translated into legislation in a number of states, as well as at the federal level.
In a get-tough measure sparked by the Hinckley incident, Idaho legislators last year voted to abolish the insanity defense. Under the law, which takes effect this month, a defendant cannot be acquitted on grounds of insanity, but he can present evidence on his intent at the time of the crime, explains Ken McClure, Idaho deputy attorney general. This means that if a defendant presents evidence that he is mentally ill and is convicted, psychiatric treatment could be called for as part of his prison sentence.
Californians voted into law on June 8 a ''victim's bill of rights'' making it tougher to prove insanity by requiring a defendant to prove both that he did not comprehend the nature of his act, and did not know it was wrong. (Prior law required the defendant to satisfy only one of these to prove insanity.)
Emerging as perhaps the strongest alternative to the ''not guilty by reason of insanity'' verdict is Michigan's ''guilty but mentally ill'' rule, by which a defendant found insane is held legally responsible for his crime. Versions of the rule have been adopted in Illinois and Indiana and are being considered in several other states.
This approach provides that a convicted criminal - sane or not - serve a regular prison sentence. The sentence can include psychiatric treatment in prison or in a mental hospital, but the law ensures the person will be held for the duration of his sentence.
Behind the search for alternatives to the insanity plea is the philosophical conviction that all who commit crimes should be treated equally. Those holding this view object to the idea of someone admitting guilt and then receiving only an indefinite period of psychiatric treatment. Thus the move toward banning the insanity defense and offering juries the option of finding a defendant guilty of a crime, while maintaining consideration of insanity in sentencing.
Mr. McClure says that in Idaho the average length of treatment for those judged criminally insane has been only 18 to 24 months. (Supporters of the insanity defense add that this average does not include the commitment period for those who have committed heinous crimes and have been put away indefinitely.)
Kim Ervin, who helped draw up a federal version of Michigan's ''not guilty but mentally ill'' rule, says she favors the definite commitment period this alternative offers. It would help keep repeat offenders behind bars by creating a criminal record which could be used as evidence in subsequent cases against them, she says. Currently, previous acquittals by reason of insanity are not admissable evidence in most courts.
Those who support retaining the ''not guilty by reason of insanity'' defense admit its shortcomings.
However, the insanity plea is not the threat to law and order that it is often portrayed to be, suggests Terry McCarthy, head of an American Bar Association (ABA) legal standards task force of judges, attorneys, and psychiatrists which has recommended retaining the defense. Historically, he says , civilized society has accorded protection to the insane, just as it does not hold children criminally responsible.
Mental health officials interviewed said media attention given insanity cases leaves the unfair impression that the defense is used by sane criminals trying to get off easy with hospital rather than prison time.
While there are no conclusive records on rates of conviction or acquittal in insanity cases, the ABA argues that only 1 percent of all felony defendants ever successfully invoke the defense, and that when they do, they end up spending more time in hospitals than they would have in prison. But others argue that 1 percent of all felony cases in the country - including those that never go to trial because of plea bargaining or dropped charges - is actually a large number.
Mr. Miller argues that current law considers the defendant's state of mind when determining varying degrees of crime. For example, he says, ''If a person does an act resulting in the death of another, in effect it could be anything from justifiable homicide, which is self-defense, . . . to premeditated murder with malice, which is first-degree murder. In every one of those the distinguishing element is usually the mental intent of the person committing the crime.''
One criticism of the ''guilty but mentally ill'' alternative is that after the convicted person has served time, he is released - sane or not. Marylin Sword, co-executive director of the Idaho Mental Health Association, says, ''There's no guarantee they won't be released, but the (prison) system doesn't guarantee that either.''
This week witnesses for the prosecution in the Hinckley trial are applying their counter-punch to testimony by defense psychiatrists. And over the whole proceeding hangs a strange irony: if the jury finds Mr. Hinckley not guilty by reason of insanity, the prosecution must do an about-face and argue he is insane in order to make sure he is locked up.