The verdict in the trial of John W. Hinckley Jr. surprised many prominent psychiatrists and legal experts, including two physicians who testified in Hinckley's defense, and rekindled debate over the proper role of psychiatrists in controversial criminal proceedings.

The experts interviewed yesterday generally agreed that U.S. Judge Barrington D. Parker's instructions to the jury last Friday greatly influenced the jury's decision that Hinckley was not guilty by reason of insanity when he shot President Ronald Reagan and three others March 30, 1981.

Parker told the jury that Hinckley had to be presumed legally insane at the time of the incident unless the prosecution could prove "beyond a reasonable doubt" that he was was sane and in control of his actions.

"I had predicted all along that the jury would find Hinckley guilty," said Dr. Alan A. Stone, a professor of law and psychiatry at Harvard University. "I thought they would ignore the judge's instructions, get confused by all the conflicting testimony, and end up with a gut reaction that Hinckley was a bad person and find him guilty . . . I was shocked with the result and it left me with a feeling of admiration for the jury. It listened to the judge's instructions."

Dr. David Michael Bear, an assistant professor of psychiatry at Harvard Medical school, said the verdict was a "victory for modern scientific methods in psychiatry." Bear had testified at the trial that Hinckley was a "defective man" on a tragic path, a contention that was ridiculed by prosecutors.

"I suspect that jury members had to struggle, as I did, to apply the complex law concerning insanity," Bear said. "However, on the basis of overwhelming psychiatric evidence, John Hinckley was correctly found not guilty under that current law."

Bear and two other experts who were hired by Hinckley's family to testify that he was legally insane at the time of the shooting acknowledged that the controversial verdict might spark renewed public criticism of psychiatrists acting as "hired guns" who tailor their testimony in criminal proceedings to meet the needs of their clients.

"I can see how some people would perceive it this way," said Dr. Ernst Prelinger, a Yale psychologist who was part of the team of psychiatric experts who testified on Hinckley's behalf.

"But we were not hired for any particular purpose except to make an evaluation (of Hinckley) and recommendations to the attorneys. There was no preconceived outcome, but rather we were asked to determine whether it would make any sense to seek an insanity plea."

Dr. William T. Carpenter Jr., director of the Maryland Psychiatric Research Center who testified that Hinckley suffered from forms of schizophrenia, said in a statement that the jury's decision would raise legal, professional and moral questions.

"The question as to whether justice has been served has been raised, but I do not believe it is my place to express satisfaction or dissatisfaction with the jury's determination of the facts," Carpenter said.

None of the psychiatrists who testified for the prosecution was available for comment yesterday. Dr. Jonas R. Rappeport of Baltimore, who was part of the prosecution's team of medical experts, said he thought the jury "gave its best decision" under difficult circumstances.

"It was obviously not a clear open-and-shut matter," he said.

Some experts strongly criticized the verdict and predicted that it would prompt Congress and state legislatures to pass laws to prevent defendants from using the insanity defense in future cases.

"The verdict is an American tragedy that does the cause of justice ill and conceivably endangers the lives of public officials by people who may be disordered but still have power to control their conduct," said Abraham L. Halpern, director of the Department of Psychiatry at United Hospital in Port Chester, N.Y.

"Now that the damage has been done, Hinckley will go down in history as the case that opens the door to a serious look" at the problems that the insanity plea poses to the legal system," Halpern said.

Robert L. Sadoff, a clinical professor of psychiatry at the University of Pennsylvania, said he could foresee a legislative backlash to the verdict that would shift the burden of proof from the prosecution to the defense in determining the insanity of a defendant.

However, Sadoff said that the criminal justice system would be better served by a clarification of existing standards for determing legal insanity and "perhaps reexamining the role that psychiatrists play" in such cases.

Others said that the infrequently used insanity plea was an essential, albeit controversial, defense in criminal law, and that some of the criticism of psychiatrists' role in the legal process is unfounded.

Dr. Richard A. Ratner, a forensic psychiatrist who practices in the District of Columbia, said that while he may disagree with the defense's contention that Hinckley was insane, "I'm not unhappy with the verdict, because the people have spoken.'

"All the people screaming and yelling and Monday-morning quarterbacking about how the law has to be changed are sore losers," Ratner said. "I don't think psychiatrists are really the villians in this . . . We take the heat for things that are really the responsibility of the courts -- of the legal system, if you will."

In a statement released yesterday evening, the American Psychiatric Association (APA) said the psychiatric community is divided over the insanity defense and that it was up to society to resolve the issue.

"Any insanity test should recognize the extent to which psychiatric knowledge can meaningfully contribute to a realistic understanding of a person's mental status and behavior at the time he commits a criminal act," the APA statement said. "Moreover, consideration of the issue of 'proof beyond a reasonable doubt' as a standard in insanity cases should reflect the fact that, much as in the case with medical knowledge generally, psychiatric knowledge on these matters cannot be expected to meet demands for absolute certainty."

The statement added: "The final moral decision -- guilty or not guilty -- always has and always will remain a jury decision irrespective of the insanity defense."