An imprecedented investigation into alleged misconduct by the California Supreme Court teetered on the brink of collapse today, when a lower state court ruled that the public nature of the probe violated the California constitution.

The state Commission on Judicial Performance, which is conducting the investigation, canceled today's hearings to consider what action it might take in response to the appellate decision. Its options ranged from appealing the decision to the state Supreme Court, to continuing its investigation despite the lower court's ruling to simply calling off the investigation, now six weeks old.

The ruling by a state court of appeals in Los Angeles came in response to a petition from Supreme Court Justice Stanley Mosk to quash a subpoena requiring him to testify publicly at the commission hearings.

The court granted Mosk's petition on grounds the state constitution required that the investigation be confidential. It did not, however, order that the commission's public hearing be stopped.

The commission can therefore continue its probe, but it must do so not only with the stigma of cunconstitutionality, but also without the testimony of Mosk, considered a central figure in the inquiry.

Adding to the commission's problems, yet another justice, Frank Newman, has also reportedly decided to refuse to testify publicly on grounds of "judicial privilege."

The commission began its investigation in the wake of news reports last fall suggesting the Supreme Court was delaying release of politically explosive judicial decisions until after the November confirmation election of four of the justices, including Chief Justice Bird. At the time, Bird in particular was under fire from right wing forces trying to block her confirmation because of her "liberal" rulings on the bench.

Release of the decisions, which included one striking down a popular law requiring prison sentences for anyone convicted of using a gun in the commission of certain crimes, could have resulted in Bird's defeat at the polls. She subsequently won confirmation with 53 percent of the popular vote.

The commission is trying to determine if there were improper delays in releasing the decision, as well as whether any justice, in violation of the judicial canon of ethics, leaked word of the alleged delays to the news media. If the charges are proven against any of the justices, they could be censured or removed from office.

Mosk's testimony is considered crucial because he reportedly told another justice last fall "it was obvious the cases were being held for filing until [after] the election," and that the justice would "have to pay the consequences." The justice in question, Mathew Tobriner, is considered an ally of Rose Bird, and was reviewing one of the controversial cases at election time.

Tobriner has denied any improper delays took place or that any such conversation with Mosk occurred.

Mosk's name has also come up repeatedly in connection with last fall's news stories about the alleged delays.

At this point, the only avenue that appears open to the commission, if it wants to compel Mosk to testify, is to appeal the lower court ruling to the state Supreme Court - the very body it is investigating.

If that happens, legal observers here predict, all seven of the Supreme Court justices would have to disqualify themselves from the case. Eight appellate court justices would then have to be chosen to replace them.