What is most striking about Samuel Alexander Adams -- the man whose theory about Vietnam has been on trial here for the last three months -- is that there is no discernible anger in his manner.

Day after day, the former CIA analyst, one of the codefendants in retired general William C. Westmoreland's $120 million libel action against CBS, has listened to the general's friends and lawyers describe Adams as obsessed, monomaniacal. Or, as his former boss at the CIA, George Carver, told the court in November, Adams "was very intolerant of people who did not share the conclusions to which he jumped."

It has become clear that this multimillion-dollar trial would not have occurred without his fixation, his dedication to what is now widely known as the "Adams theory," born 17 years ago in a cubicle at CIA headquarters when he first suspected that the U.S. government was suppressing the truth about enemy troop strength in Vietnam. It is that theory, central to a 1982 CBS documentary, that Westmoreland asserts libeled him.

For three months, Adams, who takes the stand today, has sat at the end of the defense table in U.S. District Court. Wearing rumpled tweeds, scribbling notes on his voluminous chronologies or "chronos," even taking down slurs on his own character, he shows only serenity. Outside the courtroom, he has joked with reporters, saying, for example, that Carver is "a nice funny guy, who, of course, was wrong."

Perhaps Adams' ease stems from a satisfaction that his views have finally received the public forum he has been yearning for; or perhaps it is from his belief that he is absolutely right.

"In fact, to be honest, for me this trial is a bonanza," he said during one of the periods when his motives were under strongest attack here. "I'm a researcher, but when have researchers ever had the power of subpoena?" he added, his soft voice difficult to hear even when talking about what is clearly his life's passion. "It is almost unique in that usually when these things are released, all the principals are dead."

Now, when Adams testifies as the first live witness for CBS in defense of the documentary, it will be his day in court, the ultimate airing of one of the nation's best-researched intelligence theories.

And Adams, who was a paid consultant to CBS Reports for the program, will have to convince the jury that he is stubborn only because he is principled, a man at odds with his government's leaders only because he believed they were not doing their jobs and certainly not doing their best.

Says one of his closest friends, author John Rolfe Gardiner, "I think the man is incredible -- a hero of our time. I hope they will be able to recognize it."

In some ways Sam Adams is the most fascinating and least known of the parade of characters who have been a part of this long, complicated courtroom drama over the CBS show "The Uncounted Enemy: A Vietnam Deception."

Shy, handsome, his humor almost always at his own expense, Adams has a gentle way, like a befuddled professor who recognizes that even some of his friends see his fondness for one thin slice of time and history as amusingly eccentric.

But underneath that shambling exterior, Adams is as obdurate as Plymouth Rock, a man as caught up with his version of the truth as some of his famous forebears. A fourth cousin, seven times removed, of President John Adams, the living Sam Adams (no direct kin to the American revolutionary Samuel Adams) has bloodlines deep in the American establishment.

His father, Pierpont Adams, who was probably named after Pierpont Morgan, had a seat on the New York Stock Exchange. And in one of the odd ironies of this trial, Pierpont's partner was the late Ellsworth Bunker, former ambassador to Vietnam who, had he lived, might have testified against his former partner's son.

The list of Adams' schools is consistent with such connections. He went to St. Mark's School in Massachusetts and on to Harvard (history) '55. "The same year as Teddy Kennedy, whom I didn't know," Adams says. Then there was the Navy, and after that, as if reconnoitering for the troubled young in the 1960s, there was his lost period, a youth's thrashing around to determine where to use his formidable energies.

For a while, there was ski bumming, but, as Adams put it, "I quit when the snow melted, and I didn't know what else to do." Then, like many of his old associates, he tried law school, but found Harvard's attorney factory not to his liking. Then there was banking until Aug. 16, 1962, the day after he married Eleanor McGowen, the elegant daughter of a patrician Alabama family. "Mr. McGowen must have been in shock -- this jerk . . . quit his banking job the day after he married his daughter," Adams recalled.

Having then run through most of the professions of America's gentlemanly class, Adams looked to the government, the Agency. It was an era, much like today, when the Agency lured many of the brightest and most sensitive young men out of the nation's elite colleges.

"I had no idea I would like it or that I was likely to be good at it," Adams said recently of the junior officer trainee job that he landed in March 1963.

A year later Adams began working on the Congo desk. Acknowledging that he skimmed through Harvard and dawdled at other jobs, Adams suddenly hit intellectual pay dirt at the CIA.

"I found to my astonishment that I really loved the place. I'd love to go back," he said, carefully adding, as he always does, "although I realize that's totally quixotic."

Adams began studying the tribes in the Congo, following the basic rule of good intelligence that, first, one learns everything available on the subject. Everything, he stressed, his soft voice rising only slightly for emphasis. Then, you can begin predicting, extrapolating from the known to the expected.

Adams said that such a mountain of research allowed him to predict such things as that Uganda would invade the Congo -- a notion that brought snickers, he recalled, from the State Department.

When Uganda did invade the Congo -- fulfilling his prediction about the area Adams knew only by maps and documents he memorized with a watchmaker's eye for detail -- Adams became the golden boy at the CIA.

"It was like rockets going off. It was terrific -- one of the high points in my life," he remembered recently.

"There's no crystal ball. It isn't luck," Adams said of the analyst's job. "The key to good intelligence is good files, knowing what's in them and how to retrieve them."

From the Congo, Adams was promoted to the Vietnamese affairs section at the CIA's Langley headquarters, trying to sift through documents that sometimes lie and sometimes don't, to figure out how many people were really out there fighting the United States in the early stages of this long war.

What became his 17-year-old battle with the government started in the Vietnamese town of Tan An in 1966 as he sat in a hot, dusty room looking through dossiers about communist defectors to the South Vietnamese side. When he counted the defectors in that area there were 120, but when he happened to look at the official U.S. document that showed how many Viet Cong guerrillas there were supposed to be, it said 160, he says. That should have left a scant 40 in the field -- a fact he remembers as being merely puzzling, at that stage.

A few months later, back in Washington, Adams says, he began comparing Army figures in one province that showed 50,000 Viet Cong guerrillas and militia. The official order of battle, though, said there were 4,500. He did not shout "Eureka!," but for Adams it was The Moment, the discovery that sent him hurtling into a life and obsession, seemingly against his own best interests.

"My jaw just clattered to the floor," he likes to recall. "I started galloping around the CIA headquarters like Paul Revere."

In retrospect, it may be that Paul Revere wouldn't make such a good bureaucrat. Within the agency, until he resigned in 1973, Adams became like a sorcerer's apprentice, toting enemy troop data to bosses already drowning in his carefully researched but politically troublesome numbers. Adams kept pushing for enemy troop totals that the military said were too high, that the brass believed were wrong and would turn an already skittish public permanently against this war.

When they didn't listen, Adams didn't retreat submissively to his cubicle. At first he protested, resigning from the Vietnam Affairs staff in 1968 and calling the agency's compromise on enemy data with the Army in 1967 a "monument of deceit."

From elsewhere in the agency, by the early '70s, he had begun to collect what Westmoreland's lawyers call "the purloined documents" on Vietnam -- a series of papers, many of which he hid in a leaf bag buried on his wife's 250-acre cattle farm in Northern Virginia until one sack sprang a leak and his treasured secret data began to decompose.

Friends, many of them neighbors on the posh Loudoun County farmlands, say that this may have been the period when his marriage showed early signs of strain. His wife and son began to suffer from the fears that their phone was tapped by the CIA. They shared Adams' nervousness about being followed and the concern that the CIA might try to send him to jail or, worse, retaliate in less wholesome ways, their friends recalled.

Still, Adams persisted. Within the government, he tried to have the CIA investigate its director, then Richard Helms, and he wanted the Army to court-martial Westmoreland for "fabrication" of enemy strength figures during Westmoreland's command in Vietnam. Said R. Jack Smith, who was deputy director of intelligence at the agency during Adams' tour there, "Sam is a very charming man, extremely persuasive, and it never fails to surprise me how people who only know him socially get their impression of him. Our impression in the agency was rather different."

Describing Adams as stubborn, difficult to work with, Smith said that Adams began to believe in 1967 that his extrapolation about figures from one province was the issue the war would turn on.

"He somehow failed to understand that he had a hold of part of the problem, not all of it," Smith said.

After voluntarily testifying for Daniel Ellsberg at his "Pentagon Papers" trial, making the case that the numbers Ellsberg was being tried for leaking were false anyway, Adams resigned from the agency, to the apparent relief of some of his superiors and to the dismay of a few of his fellow workers.

One CIA official who knew him well in those years and who still likes Adams said that he was one of the brightest young men the agency had seen in years. But in the end, he said, Adams was not a good analyst because he couldn't let go, he couldn't move to other fights once he had lost this one.

If there was a sense at the CIA that Adams was working at the wrong place, there is sometimes a sense with Adams that he is living in the wrong era.

After one of four visits to the Cloisters Museum and viewing the Unicorn tapestries there, Adams told reporters outside the courtroom: "I'm afraid I belong in the 12th century."

Adams' audience that day laughed, but there was an almost eerie reality to that comment, a realization that one could easily see Adams in a monk's robe, toiling in an ancient library on the most intricate details of an argument.

Thus, when Adams formally severed his ties with the agency and retired to the farm more than 12 years ago, he kept his theory afloat, traveling around the country interviewing participants in the 1967 intelligence debate about the enemy, searching, some say, always for confirmation.

Adams wrote an article in 1975 for Harper's magazine that accused the CIA of the primary sin in the intelligence business -- tainting the facts with political realities. His editor on that piece was George Crile, who went to CBS a few years later, decided to do a show drawing on Adams' theory, and hired Adams for $25,000 as a consultant for CBS.

Now a fellow codefendant in this case, Crile has said in the courtroom that he believed Adams is a "man of great confidence and in certain respects brilliance." Crile also said in court that Adams had "extraordinary integrity," even though memos suggested that Crile also believed Adams was "obsessed" and that his facts should be carefully verified elsewhere.

An attractive man, especially to women, one of whom calls him a "rustic Paul Newman" because of his compelling blue eyes and high cheekbones, Adams said he has few plans for life after the trial.

For those who knew him two years ago, Adams is suddenly gray -- not so much from this trial, they say, as from an impending divorce that has moved him away from the farm that he said provided him with one of the true joys in his life since the CIA.

"I guess I'm the only downwardly mobile WASP I know," Adams joked about his uncertain future.

"I guess if I can't go back to the agency, I'd like to be a farmer," he said. "It's the only thing else that is satisfying."