Attorney General William French Smith called yesterday for changes in federal law that would eliminate the insanity defense.

In testimony before the Senate Judiciary Committee, Smith said he preferred that approach to the more limited steps of adopting a verdict of "guilty but insane" or shifting the burden of proof from the prosecution to the defense.

Under the version supported by Smith, contained in several pending bills, accused criminals could not be acquitted by reason of insanity unless they were so deranged that they had no idea what they were doing.

"Mental disease or defect would constitute a defense," he said, "only if the defendant did not even know he had a gun in his hand or thought, for example, that he was shooting at a tree."

That change would abolish the insanity defense as far as the Constitution will allow, and "make mental illness a factor to be considered at the time of sentencing, just like any other mitigating factor," Smith said.

As a result, he said, a criminal trial will not become "a time-consuming, confusing swearing contest between opposing psychiatrists"--like the trial of attempted presidential assassin John W. Hinckley Jr., whose acquittal sparked the latest round of attacks on the insanity defense.

Since the Hinckley verdict, the major debate on Capitol Hill about the insanity defense has not been about whether to change the current law but how to cut back on it.

Among the other recommendations have been adopting: a verdict of "guilty but insane," or one that would make certain criminals like Hinckley are punished but would provide them with psychiatric treatment, or shifting the burden of proving sanity from the prosecution--which bears the burden in federal courts and 28 states--to the defense.

Associate Attorney General Rudolph W. Giuliani told the committee that merely shifting the burden of proof might increase convictions but would still allow juries to be confused by a barrage of conflicting psychiatric testimony. In addition, he said, the "guilty but insane" verdict "raises serious constitutional concerns," since it might allow convictions in cases where a defendant is so insane that "proof of knowledge or willfulness is lacking."

The current insanity defense in federal courts allows defendants to be found not guilty by reason of insanity if a mental disease or defect makes them unable to appreciate the wrongfulness of their conduct or to conform their actions to the requirements of the law.

Smith also recommended giving federal judges power to commit defendants who are found not guilty by reason of insanity.

Now, Smith said, federal judges outside the District of Columbia have no independent power to have such defendants committed, creating "the very real potential that the public will not be adequately protected from a dangerously insane defendant who is acquitted at trial."