The mysterious Argentine financier David Graiver is probably dead and cannot now be tried in a multimillion-dollar bank fraud case, a state Supreme Court judge ruled here today.

Judge Arnold G. Fraiman dismissed indictments involving at least $15 million and possibly as much as $200 million allegedly misappropriated by Graiver, "on the ground that all evidence would appear to indicate he is now deceased." The judge reserved for the state the right to reopen the case should new evidence turn up.

He said the state had provided him no new evidence other than a sealed affidavit submitted last June that Graiver, 35, was not killed in te August 1976 crash of a private jet at Cerro el Burro, Mexico, just outside Acapulco. "While it is entirely possible that Graiver may still be alive, it seems in the best interests of justice at this time to dismiss the indictments against him," Fraiman said.

Trial for three other former officials of Graiver's American Bank and Trust Company is scheduled for Feb. 5, and legal uncertainty on Graiver's status would make it difficult to determine what evidence could be submitted to a jury and what would have to be withheld for a future trial of Graiver, should be turn up, the judge said. In addition, Graiver's widow, Lidia, has been waiting two years to proceed with a $30 million wrongful death action against the charter airline involved in the Mexico crash, Walkers Cay Air Terminal nc. of Fort Lauderdale, Fla.

The state alleges that Graiver and the other AB&T officials authorized vast loans to a Graiver bank in Brussels, which then shifted the money in a kind of laundry operation to dummy corporations set up by Graiver. Mexico City's large Jewish community invested millions in the New York bank, which folded just one month after Graiver's plane crash. It was the fourth largest bank failure in U.S. history.

"Graiver's entire history with AB&T and other companies demonstrates that he was a man with wide international connections, an intelligent and capable man who would be able to conceal his whereabouts," said Assistant District Attorney Stephen Shiffrin in arguing yesterday that the indictments ought to stand.

Graiver's chartered plane, a white Falcon Dessault, crashed at full speed into a Mexican mountainside north of Acapulco Aug. 6, 1976, after making an unscheduled stop in Houston on its way from New York. The pilot, copilot and one passenger were killed.

Fragments of a badly burned body were identified as Graiver's after the Mexico crash by his brother, Isidoro, and then were cremated. The only evidence that Graiver is alive was a sealed affidavit submitted to Fraiman last June, in which the prosecution is reported to have alleged that Graiver was seen in a Florida airport after the crash by an unidentified businessman. Fraiman gave the state six months at that time to come up with better proof of Graiver's continued existence, but no new evidence was offered, he said.

Gravier's role was clearly central to the state case, and Peter Morrison, attorney for former AB&T director Saul Kagan, one of the three officials facing trial next month, was jubilant over the judge's ruling. "The grand jury didn't know it was indicting a dead man... and a lot of the evidence revolves around him," he said.

Graiver's connections that weave in and out of New York politics and international banking are expected to unravel at the February trial. The Argentine government has jailed five members of Graiver's family on grounds that Gravier was acting as banker and investment counselor for the Montonero guerrilla organization. They have charged the family with responsibility for $17 million that the Montoneros obtained in ransom for various businessmen.