A rare glimpse into the passionate inner workings of the deeply divided California Supreme Court began to unfold today as an investigating commission sought to determine whether the court had withheld controversial rulings for political reasons.

While the opening testimony before the Commission on Judicial Performance was muted and highly technical, court memos released by investigating special counsel Seth Hufstedler showed that among themselves the justices had freely accused each other of lying and intellectual dishonesty.

In a memo dated Dec. 20, 1978, Chief Justice Rose E. Bird accused Justice William P. Clark of "an affront to your colleagues and the trugh" for saying that the court had decided a case and then withheld it to help Bird win voter confirmation last November. In other memos, Clark and Justice Matthew Tobriner charged one another with providing "inaccusrate" and "false" information to the public.

The memos show that Clark was asked and refused to sign a statement by Bird declaring that the court had acted properly. In a sharply worded memo to the chief justice he said that "it must be clear to all in the court" that the case was "signed up and ready for filing well in advance of November."

"I am appalled at this statement," Bird replied in another memo. "It is untrue. Moreover, as Justice Tobriner told all of us in conference today (Dec. 20), it is directly contrary to your own statement to him . . ."

At stake is the diminished credibility of a judicial body that once was regarded as the most innovative and authoritative in the nation.

For decades, the California Supreme Court pioneered in landmark judicial decisions - most of them considered liberal - on issues of civil liberties, civil rights and the environment. Many of its decisions anticipated those made by the U.S. Supreme Court under Earl Warren, a onetime California governor.

Today the court is bitterly divided along ideological and personal lines. The extent of this was revealed last week when the court reversed itself on one of its most controversial decisions and upheld California's "use a gun, go to prison" law.

It was the striking down of that law that led to the current investigation. On Feb. 6, 1978, the court heard arguments aimed at declaring the law unconstitutional. By a 4-to-3 vote, in a decision issued 319 days later, the court ruled that the law was invalid. Tobriner wrote the majority decision, in which Bird concurred. The decision was denounced by law-enforcement agencies throughout the state.

Critics of the court charged that the decision was delayed to help Bird win voter confirmation under an unusual California law that requires ratification of Supreme Court members. Her election was the closest of its kind in history, and she eventually won with only 51.7 percent of the vote. Many here believed Bird might have lost the election if her view that the "use a gun, go to prison" law was unconstitutional had been widely known before election day.

But believing that announcement of the decision was deliberately delayed and proving it are two different things, as the commission is discovering. Most of today's hearing was occupied with the testimony of Justice Frank R. Richardson, a conservative on the court who usually sides with Clark philosophically while avoiding the emotional entanglements of some of the other justices.

Richardson's testimony, most of it concerned with the complex procedures under which justices circulate opinions, seemed to have been a help to the Bird faction. Tobriner kept the decision in the controversial gun case, known as people v. Tanner, in his posession for 108 days. Richardson indicated that he felt this was reasonable in view of the complexity of the case. And he added he had "no recollection" of any conversations concerning unreasonable delay.

Beyond that, Richardson's uncertainty about the proper amount of time necessary to reach a decision in a complicated case gave credence to an opinion shared by court observers that whatever the court did, it will be impossible to prove the motives of individual justices in doing it.

Lacking that proof, the long hearings on which the commission is embarking may serve chiefly to show that behind their black robes of neutrality the justices are emotional human beings who become as petty or as enraged about the actions of their colleagues as anyone else.

Prior to the hearings, the case was carefully investigated by Hufstedler, who produced a mountain of memos, newspaper clippings, flow charts and statistical data about the California Supreme Court. One of the most interesting, if little noticed, bits of information emerging from this collection was the finding that Justice Stanley Mosk, the swing man on the Tanner decision, had looked at the case for only a single day.

Mosk originally signed the majority decision that struck down the gun law. Last week he reversed himself and signed the new majority opinion, written by Clark, which holds that the law is unconstitutional.

Today's hearings brought renewed objections from an attorney for Justice Frank C. Newman that the proceedings violated a judicial "privilege" protecting te confidentiality on communications between justices.

The claim drew a sharp response from the commission's special counsel who said "full disclosure" of the facts was essential in the commission's performance of its duties. He cited the U.S. Supreme Court's rejection of former president Nixon's "executive privilege" claim put forward during the Watergate scandal, to buttress his argument.