John W. Hinckley Jr. is not guilty of attempting to assassinate the president because he was legally insane at the time he shot President Reagan and three others, a federal jury found last night.

Hinckley, his hands shaking, began to wipe his eyes as Judge Barrington D. Parker declared in a brusque voice that the jury had found Hinckley "not guilty by reason of insanity" on each of 13 counts in connection with the wounding of Reagan, presidential press secretary James Brady, D.C. police officer Thomas K. Delahanty and U.S. Secret Service agent Timothy McCarthy on March 30, 1981.

The jury's verdict, which cannot be appealed, means that Hinckley, a 27-year-old college dropout who faced life in prison if he had been convicted, will be committed by the court to St. Elizabeths Hospital for the mentally ill.

Within 50 days, the court must hold a hearing to decide whether he should be released because he is no longer a danger to himself or the community due to mental illness. If the court determines that Hinckley is dangerous he will remain at St. Elizabeths.

In that event, he will have the right to request a rehearing on his mental status every six months.

The jury reached its verdict at 6:20 p.m. yesterday after 24 hours of deliberation over four days. It took nearly 1 1/2 hours from the time the verdict was decided for marshals to assemble the prosecution and defense teams, Hinckley's parents and a large group of reporters in the courtroom.

While marshals hushed the crowd, the jurors filed in at 7:50 p.m. Moments later, a stern-faced Parker entered and announced that a verdict had been reached. The jury foreman and Hinckley were ordered to stand. Juror Lawrence H. Coffey, 22, stood and turned over the verdict to Parker's courtroom clerk, who handed it up to the judge. The entire proceeding, including reading the verdict on each count, took eight minutes.

Parker scheduled a further hearing, which he called a sentencing hearing, for July 12 and immediately remanded Hinckley to the custody of the U.S. Marshal Service.

Dr. Harold Thomas, a spokesman for St. Elizabeths, said he expected Hinckley to arrive at the hospital early today.

As the jury's verdict was read aloud, Hinckley's father, John W. Hinckley Sr., board chairman of Vanderbilt Energy Corp., a Denver-based oil and gas exploration company, closed his eyes and drew his hands up to his face to cry. Hinckley's mother, JoAnn, grasped her husband's hand and sighed deeply as her eyes reddened with tears.

The verdict by the jury of seven women and five men means that the government failed to prove beyond a reasonable doubt that Hinckley was sane when he attacked the president.

The jurors, looking drained and tired, were escorted by U.S. marshals from the courthouse to the hotel where they have been sequestered while considering the case. No juror had any immediate comment about last night's verdict.

Agent McCarthy told Independent Network News after the verdict last night, "Well, that's what money will do for you. I'll plead insanity too if I ever do anything like that." There was no comment from Reagan, Brady or Delahanty.

As he left the courtroom yesterday, Hinckley's defense lawyer Vincent J. Fuller smiled and quipped to news reporters, "Another day, another dollar.

"I've been here for eight weeks and I guess we are pleased it's over," Fuller said. Asked if he was pleased with the jury's verdict, Fuller responded "That's a fair statement."

Chief prosecutor Roger M. Adelman, who had urged the jury to hold Hinckley responsible for what he had done, was not immediately available for comment.

The courtroom was packed with news reporters and a few spectators as Hinckley stood with his hands folded in front of him and listened to Parker, his voice tense, quickly read off the jury's verdict.

As the crowd in the courtroom began to stir, Parker sharply admonished one of the courtroom marshals. "Mr. Marshal, if you can't keep order then get someone else who can," Parker snapped. The judge then thanked the jurors for their long service in the case and warned them he expected they would be pursued by the media for their thoughts about their decision and what they had heard during the trial.

Meanwhile the prosecution team, seated together in the well of the courtroom, remained expressionless. Law enforcement officials who had worked with the prosecution on the case were also seated in the courtroom and appeared stunned by the jury's decision.

Hinckley shook his head, sighed and looked up as it became clear that the jury had found him not guilty by reason of insanity on all charges against him. Hinckley's parents embraced during the reading of the verdict and later, in the well of the courtroom, his father embraced defense lawyer Fuller.

Hinckley, dressed in a tan suit, was quickly led away. He made no effort to speak to his parents.

Hinckley, who twice attempted suicide while in custody awaiting his trial, will be held at St. Elizabeths in the John Howard Pavilion, where defendants found legally insane in court as well as those in pretrial custody are housed. The pavilion, which has a capacity of 225 persons, has both maximum and minimum security units and a staff of psychiatrists and psychologists who work with inmates there.

The hospital spokesman said Hinckley would be held in "what could be described as a spartan private room" in that facility.

The Hinckley trial, which began with jury selection April 27, had been seen as a crucial test of the insanity defense, long hotly debated in the legal community. In six weeks of testimony, defense psychiatrists argued that Hinckley was driven by an internal frenzy to attack the president, while prosecution psychiatrists insisted he was in control of his actions and was seeking an easy route to fame.

Before any of the psychiatric experts took the witness stand, the prosecution set the stage with factual evidence about the shooting, including an extraordinary television videotape of the shocking scene outside the Washington Hilton Hotel as Hinckley fired on the president.

U.S. Attorney Stanley S. Harris announced immediately after jury selection that his office had acquiesced in a White House decision against Reagan's appearance at the trial. Brady, still recuperating from brain injury, was not called as a witness after his doctors made it clear they felt he was unable to testify.

McCarthy, who has returned to duty, and Delahanty, who has retired on disability due to the lasting effects of his wounds, both testified briefly. Prosecutor Adelman told the jury that Hinckley "mowed down" those two men to clear the path between himself and the president.

During that first segment of the trial, the prosecution called 16 witnesses and introduced more than 100 pieces of evidence, including two silhouettes of a man, full of bullet holes, which Hinckley had used at target practice at a Colorado shooting range. Other items included three dozen poems Hinckley had written on everything from suicide to lost love, an airplane hijack note found hidden in Hinckley's Washington hotel room and the letter he left behind there for the actress Jodie Foster.

"Jodie, I would abandon this idea of getting Reagan in a second if I could only win your heart and live out the rest of my life with you, whether it be in total obscurity or whatever," Hinckley wrote just before he set out for the Hilton.

"Jodie, I'm asking you now to please look into your heart and at least give me the chance, with this historic deed to gain your respect and love."

Defense witnesses said Hinckley first became interested in Foster in the summer of 1976, when he saw the movie "Taxi Driver," in which Foster played a 12-year-old prostitute who is befriended by the main character, Travis Bickle, a lonely, withdrawn taxi driver.

They said Hinckley saw the movie at least 15 times and began imitating the Bickle character, eventually buying an arsenal of weapons to match in number those collected by Bickle in the movie.

Over the objections of the prosecutors, the jury was shown the movie at the close of the defense case.

According to defense evidence, Hinckley, in the months before the shooting, traveled 10 times to New Haven, Conn., where Foster was a student at Yale University. He telephoned her dormitory room six times, speaking to her twice and recording their conversations, which were played for the jury.

The jurors also saw the love letters he left at her door and in her mailbox, full of what witnesses described as childish pleas for her affections. They heard tape recordings of Hinckley playing the guitar and singing love songs to Foster.

The defense began with long and at times wrenching testimony from Hinckley's mother and his father.

JoAnn Hinckley described her son's frightening decline into despair in the months before the shooting. She revealed that, on the advice of a suburban Denver psychiatrist, she and her husband had agreed to carry out a plan requiring Hinckley, long dependent on his parents, to be out of the family home and self-sufficient by March 30, 1981--the day he shot the president.

Hinckley's father, overcome with emotion, broke into tears on the stand as he told the jury "I am the cause of John's tragedy. . . I wish to God I could trade places with him right now."

Hinckley remained cold and unaffected as his father wept, but hours later he leaped up and stalked out of the courtroom, clearly distressed, after watching videotaped testimony in which Foster said she had no relationship with him. It was the first of five times that he left the courtroom during the trial.

Dr. William T. Carpenter Jr., the director of the Maryland Psychiatric Research Center, was the first of three defense experts to tell the jury that Hinckley suffered from forms of schizophrenia, a severe mental illness characterized by a severe break with reality, delusions, and major depression.

Carpenter described Hinckley as driven by the "inner dictates of an inner world," and said he was compelled by suicidal impulses when he fired on the president. Hinckley was trying to accomplish both his own death and a "magical union" with Foster, Carpenter said.

Dr. David Michael Bear, an assistant professor of psychiatry at the Harvard Medical School, described Hinckley as a "defective man" on a tragic path whose attack on the president may have been triggered by taking extra doses of Valium that morning.

Hinckley never took the stand in his defense.

Yale psychologist Dr. Ernst Prelinger told the jury that test results showed Hinckley was as sick as persons confined in mental hospitals.

The prosecution began its rebuttal of the defense insanity case with testimony from persons who saw Hinckley before and after the shooting.

"He was not a classical nut," testified Dr. William Brownlee, a medical doctor who examined Hinckley at the FBI Washington Field Office that evening. "It appeared to me that he was relieved that he had shot the president," D.C. police Det. Arthur E. Myers told the jury.

"He was just a normal, you know, all-American-boy type to me," said Virginia (Ginger) Aucourt, a maid at a Colorado motel where Hinckley lived in the weeks before the shooting.

Dr. Park Elliott Dietz, a Harvard forensic psychiatrist, was the prosecution's first expert witness. He testified that while Hinckley suffered from personality disorders, none was nearly severe enough to prevent him from abiding by the law or understanding that his attempt on the president's life was wrong.

Hinckley had a longstanding interest in fame, Dietz said, and he saw his attack on Reagan as an easy route to that goal when all else failed. Hinckley, by then angry at Foster for her rejection of him, still wanted to impress her and believed the shooting would achieve that, Dietz testified.

The prosecution rested its case on the testimony of Dr. Sally A.C. Johnson, a staff psychiatrist at the federal correctional institution at Butner, N.C., who evaluated Hinckley's state of mind in 55 interviews that began just four days after the shooting.

She collected Hinckley's thoughts before he talked to any psychiatrists retained by either the prosecution or the defense. She concluded that he was criminally responsible for his attack on the president.