The Supreme Court ruled 5 to 3 yesterday that an Indiana judge who approved the sterilization of a 15-year-old girl without her knowledge or consent performed a "judicial act" and consequently was absolutely immune from being sued for damages.

The dissenters accused the majority of relying on a "factually untrue" definition of a judicial act and of wrapping immunity around "lawless conduct." The majority rejected the accusations.

The intensity of feelings evoked among the justices became obvious in the hushed chamber of the court after Justice Byron R. White briefly summarized the 15-page opinion he wrote for the majority.

Normally, that would have ended the matter. In recent years, dissenters only infrequently have given opinions from the bench.

Yesterday, however, Justice Potter Stewart read aloud most of his five-page dissent, in which he was joined by Justices Thurgood Marshall and Lewis F. Powell Jr.

Chief Justice Warren E. Burger, one of the majority, was at Stewart's right as the dissenter spoke in a strong, controlled voice. As one cutting phrase tumbled on another, Burger's face reddened. Other justices also appeared struck observers as almost palpable.

The decision is one of a very few on judicial immunity, which is intended to assure that a judge will act independently, without fear of personal consequences, even if occasionally at the expense of legitimate individual grievances.

In a milestone ruling in 1872, the court held judges absolutely immune from monetary liability "for judicial acts, even when such acts are in excess of their jurisdiction, and are alleged to have been done maliciously or corruptly."

The act in question in yesterday's case was done by an elected judge in his 20th year on the bench, Harold D. Stump of DeKalb County in northwest Indiana.

In 1971, Warren G. Sunday, a lawyer, presented him with a petition from Ora McFarlin for approval of a tubal ligation to be performed upon his daughter, Linda, then 15, in "the best interest" of the child.

Linda "is considered to be somewhat retarded, although she is attending or has attended the public schools," McFarlin swore. In addition, Linda, on "several occasions," had spent the night with young men.

Stump approved the petition without notice to Linda, without a hearing, without the appointment of a guardian for her interests and without leaving a public record. He signed the paper as "Judge, DeKalb Circuit Court."

Six days later, Linda entered DeKalb Memorial Hospital, having been told that her appendix would be removed. In fact, Dr. John Hines performed both an appendectomy and a sterilization. Both the physician and the hospital by the petition approved by the judge.

Two years later, in 1973, Linda married Leo Sparkman. Her inability to become pregnant led her to the discovery that she was sterile. Invoking a Reconstruction-era civil rights law. Protesting loss of potential fatherhood, sought an additional $500,000.

The defendants included McFarline, her lawyer, the physician, the hospital and Stump. The Supreme Court left it to lower federal courts to decide whether its immunization of the judge requires dismissal of the other defendants.

A federal judge ruled for Stump, but was reversed by the 7th U.S. Circuit Court of Appeals. It said Stump had not acted "within his jurisdiction" and had forfeited immunity by disregarding "elementary principles of due process."

To validate his conduct would be to sanction "tyranny from the bench," the appeals court said. But the Supreme Court overturned the appeals tribunal, saying that under Indiana law Stump's approval of the sterilization petition was a judicial act - "a function normally performed by a judge."

In dissenting, Stewart said that a judge's conduct does not become "judicial" merely because he says it is. "A judge is not free, like a loose cannon, to inflict indiscriminate damage whenever he announces he is acting in his judicial capacity," he said.

He said that it was "factually untrue" that Stump's act was one "normally performed by a judge," noting that no other Indiana judge ever has done it, and terming it "beyond the pale . . . " For the court, White noted that Stewart didn't "dispute that judges normally entertain petitions with respect to the affairs of minors."

Stewart found a "total absence of any of the normal attributes of a judicial proceeding" cited by the court in 1967. "There was no 'case' . . . no litigants," he said. "There was an could be no appeal. And there was not even the pretext of principled decision-making.

In reply, White said, "Courts and judges often act ex parte" - with only one party represented.

Powell, in a separate dissent, said he was most troubled by the elimination "of any possibility for the vindication of (Sparkman's) rights elswhere in the judicial system."