A jury of eight women and four men today declared Claus von Bulow not guilty of trying twice to kill his wife, heiress Martha (Sunny) von Bulow, with injections of insulin.

If only for a moment, all the noted poise and aristocratic bearing escaped the Danish-born socialite. As the jury foreman pronounced the verdict, von Bulow shut his eyes and bowed his head as if in prayer. When he opened his eyes again, they were rimmed red and brimming with tears.

Von Bulow shook hands with his attorneys, Thomas Puccio and John Sheehan, and tried to regain his accustomed composure. Two rows behind the defense table, von Bulow's companion, French citizen Andrea Reynolds, wept uncontrollably into a tissue and clutched her stomach as if to soothe her own trembling. There was applause, even a few muffled cheers. In the back of the mobbed courtroom, a woman fainted into a man's arms. "Thank God," she said before passing out. "Justice is done."

So ended a trial that had all the broad gestures and gaudy trappings of soap opera: fantastic wealth, sexual infidelity, sibling rivalry and crime. Indeed, the trial was broadcast live for two months on cable television.

"I'm very relieved and, above all, I'm grateful to my attorneys," von Bulow, 58, said later at a press conference. "It's been five years of worry." Assuming the tragic mantle, von Bulow said the purpose of the trial was "suffering."

Von Bulow was convicted on the same charges three years ago after the jury deliberated for 37 hours, but the Rhode Island Supreme Court overturned the ruling on technical grounds. During this trial the defense relied solely on medical testimony and did not call von Bulow himself to the witness stand.

Assistant Attorney General Henry Gemma Jr., who led the prosecution with Marc DeSisto, said he was "disappointed" with the verdict. The two prosecutors walked away from the hundreds of cameras, notebooks and microphones that have been fixtures here since the beginning of the trial. The state spent more than $120,000 on the prosecution, not including salaries of lawyers and court officials, according to state officials. Von Bulow's stepchildren, his chief accusers, said they spent more than $400,000 in their private investigation, which led to the indictment.

The prosecution had accused von Bulow of trying to kill his wife in 1979 and 1980 at Clarendon Court, their mansion in Newport, R.I., in order to marry his then lover, former soap opera actress Alexandra Isles, and to inherit approximately $14 million of her $75 million utilities fortune. Testimony about the family's finances was permitted at the first trial, but disallowed at this one. The state was also not allowed to present arguments that Sunny von Bulow had struggled with an assailant before the coma she remains in.

The prosecution was able to persuade Isles to return from Europe and repeat her 1982 testimony that she had given him a deadline for divorcing his wife shortly before the first coma. She also testified he told her of watching his wife suffer for hours during that coma before deciding he could not go through with letting her die.

Revived after a brief coma in 1979, Sunny von Bulow, 53, has been in an irreversible second coma since December 1980. Doctors say she could live another 30 years. The defense denied the presence of insulin, contending that Sunny von Bulow's condition was brought on by a combination of drugs and alcohol.

Claus von Bulow, who had once been an aide to oil magnate J. Paul Getty, lives off the income of a $2 million gift from his wife. Now that he has been cleared of criminal charges, he is eligible to be one of the beneficiaries of his wife's estate when she dies. He said in an interview that he plans to take a job.

Von Bulow's stepchildren, Annie-Laurie Kneissl and Alexander von Auersperg, spent more than $100,000 in legal fees pursuing the case against their stepfather. At Clarendon Court today, they watched on television as jury foreman Robert Rocchio read the verdict at 11:23 a.m. A few minutes later Kneissl told a friend, "Good guys don't win."

Later at a news conference near the courthouse, Kneissl, 27, and von Auersperg, 25, criticized Judge Corinne P. Grande of being "pro-defense" and disallowing several pieces of evidence that were allowed at the first trial.

"But neither Claus von Bulow nor the jury's verdict can take away what our mother was, a loving, caring person," von Auersperg said. "Claus von Bulow only succeeded in depriving our mother of meaningful life and getting away with it. We know and he knows that he tried to murder our mother."

Claus and Sunny von Bulow married in 1966. He still wears a wedding ring. Their only child, Cosima, 18, has sided with her father since the case began. She did not appear at court today, staying instead at the Biltmore Hotel several blocks away. Cosima von Bulow has not been in contact with her stepbrother or stepsister since the conviction in 1982. Claus von Bulow said today he would never return to Clarendon Court -- "It has too tragic memories for me" -- but he said he hoped Cosima would be able to use the mansion "undisturbed."

The morning began with predictions among trial-watchers that a verdict was coming. Late Sunday afternoon, the jury had sent a note to Judge Grande that "considerable progress" had been made. Since beginning its deliberations Friday afternoon, the jury had reheard testimony of four medical experts. They also asked to rehear the testimony of von Auersperg and Maria Schrallhammer, the family maid, who had said she had found a "little black bag" containing needles, syringes, insulin and various drugs.

For the last four days, reporters crowded the hall outside Courtroom 8 of the Rhode Island Superior Court and waited for a decision. This morning von Bu low stood in the hall and joked with reporters about a film version of his story.

"To make a good film of it," he said, "you'd have to do something like 'The Robe,' the one with James Mason."

Asked who he would like to have play the part of Claus von Bulow, he answered, "Woody Allen."

Von Bulow has, in fact, sold the movie rights to Warner Bros. and he has reportedly arranged to write memoirs for St. Martin's Press.

At 10:50 a.m. a court official put out the word: a verdict was ready. Suddenly the atmosphere became tense, charged. Von Bulow's jaw, a magnificent mechanism that he uses to indicate everything from tension to disdain, began thrusting and clenching.

Reporters and locals jammed the doorway, waiting half an hour to be seated.

For the occasion, von Bulow wore a most elegant suit, a gray-blue English custom-made model with cuffs on the jacket sleeves. He sat next to Puccio. And they waited.

Finally the jury's arrival was announced. Twelve people marched past von Bulow and not one looked him in the eye. He tried to catch a glance, a sign, but no one gave it away.

The doors were locked. Grande ordered Court Clerk Dennis SaoBento to read the charges to jury foreman Rocchio, a state social worker from Cranston. What had the jury decided "on the charge that the defendant on December 27, 1979, committed the crime of assault with intent to murder?"

"Not guilty."

Scattered applause and gasps. Von Bulow clenched his hands together and breathed deeply.

And of the charge of attempted murder on Dec. 21, 1980?

"Not guilty," the foreman said once more.

Von Bulow bowed his head to his hands and Reynolds wept loudly. DeSisto and Gemma sat motionless at the table while the defense lawyers tried, without success, to contain their glee.

"A judgment for acquittal is given on both counts," Grande announced. "The defendant is released on his own recognizance."

Reynolds raced to von Bulow, kissed him lightly and said, "May I come with you, darling?" But von Bulow was a man in a daze and he seemed unable to respond with his usual assurance. Asked what he would do now, he said, "My daughter comes first."

Later, when he had gathered his thoughts, von Bulow said he was "not vindictive" toward his stepchildren. He said he would take a vacation and "lead a quiet life, ceasing to be in the public life."

Asked if he would divorce his wife to marry Andrea Reynolds, von Bulow ignored the question. He did say his wife would stay on life support systems at New York's Columbia Presbyterian Hospital.

On her way out of the courtroom, Judge Grande said, "This is a jury who clearly hasn't had any trouble coming to a verdict." She also said the jury was "very fixed" on the idea of not speaking to reporters. Later, Charles H. O'Connell, a juror who is city finance director of East Providence, said he said he had "no problem" with his decision and believed none of the other jurors did.

The most damning testimony against von Bulow came from Schrallhammer, von Auersperg and Alexandra Isles -- the latter appearing at the last minute. But the jury had apparently been convinced by Puccio's use of nine medical experts. Puccio painted the defendant as a cad but said charges that he would attempt murder were "monstrous."

Compared with Puccio, an experienced New York prosecutor who handled some Abscam cases, the prosecution often appeared inexperienced and outmatched to courtroom observers. DeSisto, who handled the closing argument for the prosecution, has been out of law school just three years.

At the same Holiday Inn where they have been sequestered for two months, the jurors held a party lubricated by six bottles of champagne and two cases of beer. Von Bulow and Reynolds stopped by the hotel to offer their thanks.

Of the jury that acquitted him today, Claus von Bulow said, "They spent a lot of time working hard and I am grateful."