ALL THE facts would appear to indicate he is not alive," says James P. Hoffa, who is the son of the famed Teamster boss. "We have the disappearance - that certainly speaks for itself."

Three years ago today, the notorious, the sensational and the one-time criminal James R. Hoffa was seen leaving a restaurant in the Detroit suburbs - and was not seen again. Ever. No body has been found; no one has been indicted. One of the reputed Mafia figures under investigation has been slain and other witnesses invoked the Fifth Amendment before an investigating grand jury.

Nonetheless, Hoffa's son says, "I am encouraged that the government investigation is continuing and that pressure is being put on certain people mentioned as being allegedly involved. I would like to see the effort intensified more."

But government sources are still investigating. "The case is still active," says Paul Coffey, head of the Justice Department Organized Crime Strike Force in Detroit.

And that's about all he'll say, too. "Every year about the 30th of July we get all these stories," he complains, "and I really don't think the discussion (of the case) will do us any good. It isn't because we're sensitive about now having found Hoffa, either. It's not that."

On the day Jimmy Hoffa disappeared, he allegedly told acquaintances he was on his way to see New Jersey Teamsters boss Anthony Provenzano and an old friend, Anthony (Tony Jack) Giacalone. Both men deny they had an appointment with Hoffa that day.

In June Provenzano was sentenced to life imprisonment after he was convicted for the 1961 murder of a union foe.

Jimmy Hoffa grew up a tough, feisty and poor grade-school dropout, who used to hang around the warehouse district in Detroit.

The Teamsters Union he would end up heading grew fat and rich during World War II Violence was part of his history - so was money, occasionally used to make friends and influence people.

In 1965 two California professors wrote in "Hoffa and the Teamsters. A Study in Union Power" that they'd heard him "regretfully explain that had he not expected a violent, early death, he would gladly have acceded to his wife's desire for a larger family.

In 1967, Hoffa was convicted of mail fraud and jury tampering and sentenced to 13 years in prison - a prison from which he ran the union until 1971, when he turned it over to Frank E. Fitzsimmons, his hand-picked successor.

In that same year, President Nixon commuted Hoffa's sentence on condition that he refrain from union activity for nine more years. Later Hoffa would accuse Fitzsimmons with helping to insert that provision and promising support to Nixon in '72. Later too, Fitzsimmons would deny those charges.

No one knowledgeable is speculating for public consumption on what happened to Jimmy Hoffa three years ago. Was he rubbed out by his friends, his enemies or both? Was he in fact rubbed out at all? Investigators are still checking.

"As far as the family is concerned," says James P. Hoffa, "there's never enough being done."

Hoffa, the elder, offered this intriguing insight to Professors Ralph and Estelle James in '65: "He is fond of stating that a professional killer can be hired "just like that (with a snap of fingers) for a mere $2,000 . . ."