A California Supreme Court justice's sworn testimony before an investigatory commission was directly contradicted today by one of his colleagues.

Justice William Clark told the Commission on Judicial Performance that Justice Stanley Mosk had stated last fall he feld that politically explosive court decisions were being delayed until after the November elections, when the appointments of three justices were up for confirmation by the voters.

Clark testified that in January Mosk told him that before the election he had made known to Justice Mathew Tobriner his view that "it was obvious the cases were being held for filing until [after] the election."

Clark's recollection of Mosk's statement contradicted testimony by Tobriner that, as late as a month after the election, no other justice had suggested to him any improprieties in the filing of the cases. Tobriner added that Mosk signed a statement on Nov. 9 saying "neither the final determination nor the filing of that decision [in one of the cases] has been delayed for a political or any other improper reason."

Today, Clark said that in two conversations with Mosk, one as recently as a week ago, Mosk told him of the pre-election discussion, in which Mosk reportedly also warned Tobriner "it if [the delay] were revealed or exposed, he [Tobriner] would have to pay the consequences."

Mosk's statements, as recalled by Clark, marked the first time in the three-week-long hearing by the commission that anyone has directly testified there was potential wrongdoing in the court's handling of the cases.

The commission started its investigation following news reports last fall charging that the court had delayed several decisions for political reasons - namely to avoid any adverse effect they might have had on the elections.

Clark's testimony drew a sharp response from attorneys representing both Tobriner and Chief Justice Rose E. Bird, who claimed his statements were hearsay and not admissible. At the heart of their concern, they said, were news reports suggesting that Mosk might refuse to testify before the commission, precluding confirmation o Clark's conversations with him.

The commission took the objection "under advisement" pending the outcome of Mosk's appearance scheduled for next week.

Earlier in th day, Clark said he felt one court decision had been ready for filing in advance of the November election. As of early September, Clark testified, all seven justices had rendered opinions on the case involving the state's "use a gun, go to prison" law, and he said he found it "unusual" that "four months . . . elapsed before it [the decision] saw the light of day."

The court struck down the law a month and a half after the election, but later reversed itself.

"In light of court practices," Clark stated this morning, "it would be unusual for two months, much less four months, to roll by before the filing of the case."

Clark also admitted under questionig today that he may have been a source of an election-day report in the Los Angeles Times charging that the court was delaying decisions until after the election. Clark said that, in response to questions from a Times reporter, he may have provided partial confirmation for the story.

The question of "news leaks" from members of the court, which could violate a judicial canon of ethics, also came up at the beginning of the session when Bird reversed an earlier position and agreed to supply the commission with information on possible breaches of confidentiality of the court.

On Monday she refused to answer questions regarding information about the news leaks that had been gathered by members of her staff. She claimed then it was privileged information collected to aid her attorneys in the proceeding.

Today, however, Bird provided the commission with a sworn declaration answering many of the questions. She stated, in effect, that the information gathered by her staff was only speculative or analytical and contained no factual evidence not already made available to the commission.

In response, the commission deferred any effort to compel her to testify further on the matter.

The commission's hearings resume tomorrow with further testimony by Clark.