A new controversy swirls around the insanity plea in criminal trials. It centers on the validity of psychiatric testimony and the legal liability of psychiatrists for their treatment.
As the nation approaches the second anniversary (March 30) of the assassination attempt on President Reagan, a number of events have heightened the debate:
* Former White House press secretary James Brady and two law enforcement officers who were shot during the attempt on the President's life in 1981 are suing John W. Hinckley Jr.'s psychiatrist. In the suit, filed March 18 in US District Court in Denver, the plaintiffs charge that Dr. John J. Hopper Jr. misdiag-nosed the gunman's condition before the shooting, prescribing incorrect drugs and therapy for his condition. The suit asks $14 million in damages.
* The House Judiciary Committee's Criminal Justice subcommittee is drafting a bill that would restrict the use of the insanity defense and likely redefine the role and validity of psychiatric testimony. In 1982, Congress failed to pass any new legislation along these lines, despite strong pressures from conservatives and others to do so.
* The American Psychiatric Association (APA) is calling for a ''tightening up'' of the standards and procedures to protect the public against premature release of potentially dangerous individuals convicted of serious crimes but found ''not guilty by reason of insanity.''
Last June, Mr. Hinckley was acquitted by reason of insanity of charges he tried to kill Mr. Reagan and committed indefinitely to a Washington, D.C., mental hospital. Following that verdict - which could lead to the release of the defendant once it's proved he is no longer mentally ill or dangerous - there have been attempts in Congress and several states to eliminate or limit the insanity defense. Eights states have replaced the ''not guilty '' verdict with ''guilty but mentally ill.'' And others now are considering similar measures.
The Reagan administration, and conservatives in general, seem to favor this change. The American Bar Association and civil rights groups warn that it may not be just to hold legally responsible those judged to be mentally incompetent.
However, the question of whether those who judge mental competence and prescribe treatment can be held criminally liable for their professional assessments is a new twist.
The civil suit, brought by Secret Service agent Timothy J. McCarthy and Washington police officer Thomas K. Delahanty, along with Mr. Brady, accuses Dr. Hopper of negligently prescribing Valium and certain types of therapy for Hinckley for several months before the incident.
''Dr. Hopper knew or should have known that Hinckley posed a danger to himself or others and was capable of attempting a political assassination,'' the suit says. And it adds that the psychiatrist had a responsibility to warn law enforcement officials of this potential danger.
The plaintiffs insist that Hinckley's parents wanted him placed in an institution, but Dr. Hopper advised against it, saying it would make a ''cripple'' out of him.
During the Hinckley trial, Dr. Hopper testified that the defendant gave him no hint of behavior that might lead to an assassination attempt. It was alleged that Hinckley had stalked two presidents, practiced shooting at a rifle range, and read books on past assassinations.
The APA, which represents 28,000 US psychiatrists, says it opposes any law or litigation that would hold its members legally responsible for violent crimes committed by current or former patients. It stresses that psychiatrists have no special knowledge or ability to predict violent behavior.
The APA advocates limiting the use of the insanity plea but not eliminating it as a defense. And earlier this year, the association criticized procedures in many states that require periodic psychiatric assessments of whether a patient is still dangerous. Loren Roth, a professor of psychiatry at the University of Pittsburgh, who chaired the group that studied the issue, explained that psychiatrists ''have great difficulty in predicting dangerous behavior.'' He said the best indicator of future violence was a record of past violence - not psychiatric diagnosis.
Also under scrutiny are laws that govern the circumstances under which someone in custody as a result of a ''mentally ill'' finding may be released. A federal statute holds that release may come only after proof is offered that the defendant is no longer incapacitated or dangerous. However, in March, a three-judge federal panel declared this law unconstitutional, placing the burden of proof for continued incarceration on the government.