Dr. Mario Jascalevich was acquitted yesterday of murder in a case that brought a confrontation between a defendant's right to a fair trial and a reporter's right to protect confidential sources.

A Bergen County, N.J., jury deliberated less than three hours before finding the Argentinian-born surgeon innocent of charges that he injected three patients with lethal dosed of the muscle-relaxant curare at an Oradell, N.J., hospita in 1965-1966.

The verdicct ended an eight-mouth-long trial that became the starting point for a test of constitutional rights when Jascalevich's attorney subpoenaed New York Times reporter M.A. Farber's notes and Farber refused to hand them over.

Jascalevich was indicted in May 1976 as a redult of Bergen County prosecutors' decision to reopen the 10-year-old case fellowing Farber's investigation of the mysterious hospital deaths.

Jascalevich's lawyer, Raymond A. Brown, argued that there was a conspiracy by Farber, former Bergen County prosecutor Joseph Woodcock and New York City medical examiner Michael Baden against Jascalevich, and that Farber's notes were vital to the surgeon's defense.

Farber was sentenced to six mouths in jail for criminal contempt and an indefinite term for civil contempt for refusing to surrender his notes to trial Judge William Arnold for Arnold to determine whether they shouldbe furnished to the defense.

Shortly before the jury returned its verdict, Farber was ordered released from jail on the indefinite term because testimony in the murder trial had ended. Superior Court Judge Theodore Trautwein, who sentenced Farber last summer, said that continued imprisonment could no longer compel Farber's compliance with the court since the case had gone to the jury.

Before ordering Farber freed, Trautwein said to him, "I assume you are still adamant in your refusal to obey the order of the trial court to turn over materials and notes . . . on the grounds that to do so would violate your First Amendment rights and the New Jersey shield law privilege."

"Yes," the newsman replied.

"You and only you, Mr. Farber . . . know whether you withheld something from the trial court and the jury which would have been of aid in the search for truth," Trautwein said. "You chose to put your privilege and your concept of your constitutional rights . . . above therights of the people of this state and the defendant."

After his release, Farber, 40, said, "When I was sentenced July 24, I told the court I did not have the material that would establish the innocence or guilt of this defendant and that holds true today."Farber spent 40 days in jail. His appeal of the contempt convictions is before the U.S. Supreme Court, and Trautwein stayed the six-month jail term pending the Supreme Court's decision.

The New York Times has paid a total of $285,000 in civil and criminal contempt fines.

Times Executive Editor A.M. Rosenthal estimated that the cost to the newspaper of the Farber case toatls $1 million. "Many newspapers throughout the coutry may be worried about the precedents set by these fines," Rosenthal said.

Farber and The Times argued that New Jersey's shield law, which gives reporters the right to protect confidential sources, and the First Amendment to the U.S. Constitution entitled Farber not to comply with the court's order to yield his notes for inspection.

Farber, however, was not refusing his notes to an arm of the government as in other, earlier cases, but to a defendant on trial for his life. Again and again, Jascalevich's attorney told judges that the surgeon was being deprived of his Sixth Amendment guarantee of a fair trial, and the judges, including the New Jersey Supreme Court, agreed.

Spectators greeted Jascalevich's acquittal with applause and cheers. "I'm very happy," said the 51-year-old doctor who did not testify during the trial, but had sat silently taking page after page of notes in what became the longest murder trial in New Jersey history.

Many of the regular trial spectators were friends or patients of Jascalevich who talked with him during the frequent trial recesses and made no secret of their opinion that he should be acquitted.

There were also a handful of courtroom regulars who held the opposite opion. These were for the most part relatives of the other doctors at Riverdell Hospital who were among Jascalevich's accusers. Jascalvich had said that he was accused by other doctors who were jealous of his successes and wanted to derail his flourishing career.

The motive attributed to Jascalevich was as bizarre as the idea of a doctor becoming a poisoner. It was said that Jascalevich had killed surgical patients of other doctors to damage his rivals' records. None of those who died mysteriously was a patient of Jascalevich.

Much of the trial was devoted to conflicting evidence from medical experts on whether or not curare could be traced in bodies that had been buried 10 years.

In addition to doubts about Jascalevich's guilt raised by medical experts who disputed the prosecution's evidence about curare in the exhumed bodies, there was no eyewitness who testified to seeing Jascalevich give an injection to any of the patients who later died.

Vails of curare were found in Jascalevich's locker, but he said he had been using the drug, which leads to death by asphyxiation, in experiments on dogs.

After hearing from 76 eyewitnesses and listening as 389 exhibits were introduced into evidence, the speed with which the jury reached its verdict indicates that jury members were never satisfied by the prosecution's reconstruction of 12-year-old events. Several key figures in the case had died, and several documents, tissue samples and tape recordings that might have shed light on the case had been lost or destroyed by the time Jascalevich was indicted.