Mafia chieftain Santo Trafficante Jr. refused to tell a congressional committee yesterday whether he had advance knowledge of the 1963 assassination of President Kennedy.

Subpoenaed by the House Assassinations Committee for its first hearing into Kennedy's murder, the nattily dressed, grand-fatherly looking Trafficante invoked his constitutional rights in response to every question put to him at the crowded session.

Fourteen times in all, the Florida underworld boss hunched close to th microphone in front of him and declared in a calm, pat monotone that:

"I respectfully refuse to answer that question pursuant to my constitutional rights under the First, the Fourth and Fifth and the Fourteenth Amendments."

The committee's chief counsel, Richard A. Sprague, conducted most of the interrogation, asking Trafficante about his participating in CIA-sponsored plots in the early 1960s to assassinate Cuban premier Fidel Castro, about reports that Trafficante predicted Kennedy's "hit" more than a year in advance, and about rumors that Trafficante may have been acquainted with "an American gangster type named Ruby" years before the President's death.

Sprague laid no factual groundwork on the record before asking any of his questions, but committee Chairman Louis Stokes (D-Ohio) insister to reporters afterward that the committee had legitimate grounds for posing them. Stokes acknowledged that Trafficane's attorneys had indicated in advance that the witness would decline to answer the committee's questions.

"I thought we had propounded some rather important questions," Stokes said. "It's unfortunate we were unable to ge the answers."

When pressed to justify the questions about Jacky Ruby, however, Stokes declined, saying that he was "not at liberty to disclose publicly what the investigation has developed at this point."

But a number of the allegations, while never satisfactorily developed or substantiated, have long been in the public domain.

For instance, a Cuban exile named Jose Aleman, who reportedly became involved with Trifficante in 1962 in connection with a possible Teamsters Union loan, was evidently the source of reports that Trafficante may have known the President's assassination was coming.

The Washington Post reported last year, in an article by journalist-author George Crile III, that Aleman had a long discussion with Trafficante in Aleman's Miami Beach motel around September 1962. According to this account, the discussion eventually turned to the Kennedy's, about whom Trafficante complained, saying they were not honest and did not keep a bargain. Trafficante was quoted as saying:

"Have you seen how his brother is hitting Hoffa, a man who is a worker, who is not a millionaire, a friend of the blue collar? He doesn't know that this kind of encounter is very delicate. Mark my words, this man Kennedy is in trouble, and he will get what is coming to him."

When Aleman reportedly argued back that Kennedy would be reelected, Trafficante was said to have replied, "No, Jose, he is going to be hit."

An FBI informer at the time, Aleman assertedly reportedly the conversation to his bureau contacts, but they were described an interested only in Trafficante's business propositions, and Aleman assumed they dismissed the Kennedy talk as gangland braggadocio.

The questions concerning Jack Ruby turned on Trafficante's days in Cuba, where he was overlord of syndicate gambling in Havana before Castro topplied the Batista government in the 1959 revolution and closed down the casinos. Trafficante was even lodged for a time in a Cuban jail.