The most vivid image of John W. Nields Jr., the chief House counsel to the Iran-contra hearings, is that of the set-jawed lawyer with longish hair locked in confrontation with the star witness. In the aftermath, Oliver North emerged as an object of national fascination, and some blamed Nields' questioning for spawning the obsession.

Nields, for his part, appears unfazed with the response to the lieutenant colonel's testimony.

"I think it's a healthy sign," Nields says. "I think the public should react to all this -- in all its facets. Ultimately, people are going to have to make judgments."

Everyone has a different view of Nields. Depending on where you stand, he's been confrontational or persistent, overstepping his bounds or pursuing his mandate. Today he leads the questioning of one of the last key witnesses -- Attorney General Edwin Meese III.

Nields, 44, has been both prosecutor and defense attorney -- "it's a whole lot easier for prosecutors; it's uphill for defense attorneys" -- and now handles criminal and commercial litigation at the Washington firm of Howrey and Simon, where he is a partner.

He was chief counsel to the 1977-1978 House investigation of Korean influence peddling on Capitol Hill. As a Justice Department special counsel, he won a landmark case against two former top FBI officials -- W. Mark Felt and Edward S. Miller -- found guilty of violating Fourth Amendment rights by approving illegal break-ins at the homes of friends and associates of the radical Weather Underground.

Although Nields is tight-lipped about the Iran-contra hearings -- he refuses even to discuss their impact -- he has given clues about his thinking. In his statement to the jury in the 1980 Felt-Miller trial, Nields said:

"You will hear the sounds of the Weatherman bombs ringing in your ears. We ask you also to listen for the sound of the Constitution of the United States. It doesn't make quite as much noise as the Weatherman bombs. It doesn't shriek at you. It doesn't even whisper. It just sits there silent, as it's done for 200 years, through war and depressions, through good times and bad."

Perhaps the most telling glimpse of John Nields may be found in his defense in 1983 of Mary Treadwell, the controversial Washington businesswoman and former Youth Pride Inc. official who was charged with conspiring to defraud the federal government of funds. Nields was her court-appointed lawyer.

They were, to say the least, a study in contrasts. "John's background is very white Anglo-Saxon Protestant," says Treadwell, who is black and a former street activist, "and I came from a different situation where I felt I was under attack. At a certain point, John was able to say to me, 'Look, it's not the system. When you go after a crime, you don't make mistakes. When you go after a person, that's when you make mistakes.' He was saying don't lose faith in the system."

He worked relentlessly on the case. His 20th wedding anniversary was celebrated in the office. His wife Gail brought the Chinese food and Treadwell joined them. As Treadwell recalls, there was no document unread, no move unanticipated, no slacking of his intense commitment to the case.

"John Nields made an opening statement that almost made me cry," Treadwell says.

Treadwell was convicted in 1983 and served 18 months in the federal prison for women at Alderson, W. Va.

"It was John Nields who drove me to Alderson," she says. There was no way I could discourage him from doing it, and I think the trip was more traumatic for him than me."

"She's an extraordinary lady," Nields says. "I don't believe in her perfection but I do believe in her innocence of the charges."

But Nields says he "made a very bad mistake" in the Treadwell case. "I had a tactical decision to make whether to call a witness." He decided against it. "I thought the case was morally won already. I second-guessed myself."

Of the verdict, Nields says, "If I could change one thing in my legal career, that would be it."

"I think he's partisan and biased, but I think he's a darn good lawyer," says Iran-contra committee member Sen. Orrin Hatch (R-Utah). "I think he drones on and on too much ... He could have gone through in half the time."

"I have heard some of those remarks suggesting that he spent too much time {questioning North}," says Sen. Daniel Inouye (D-Hawaii), the Senate chairman, "but to those critics, my response is a simple one. His questioning resulted in a daily avalanche of headlines. Now these headlines just don't spout out. Somebody has to dig them out, and the job that he did, considering that we had a new American hero, was not one that any one of the panel would have cherished.

"Obviously," Inouye continued, "he does not have the pizazz and charisma of a Perry Mason, but I can assure you as a fellow lawyer he's a very good one."

His critics fault Nields' approach with North as adversarial and inadvertently shoring up public sympathy. But others say that Nields was essentially put in a no-win situation.

"I think Olliemania is a function of Ollie, not a function of who among that banc was doing the questioning," says Watergate prosecutor Richard Ben-Veniste. "I don't think it would have been too much different if Donny and Marie were doing the questioning."

Scott Armstrong of the National Security Archive says that the entire Iran-contra investigation has been much too quickly paced with few real behind-the-scenes investigative sessions before the hearings. "My guess is he's asking about a tenth of what he thinks needs to be asked," Armstrong says of Nields.

Nields says only, "I feel reasonably satisfied with the way in which the hearings have gone."

As to whether he's taking too long with witnesses, Nields says, "I think the members just have to make their own judgments. If they feel I've taken too long, they'll have to act on that."

To Hatch's charge, he says, "I never felt I was partisan. I don't feel it's a partisan proceeding."

What he will say is that he finds himself in a strangely nebulous position as a lawyer.

"It's not a win-lose goal," Nields says. "I'm in a very unusual role for me as a lawyer ... More than any other legal job I've had, I'm working for a client -- namely the committee -- in an area where they are the experts and not me."

In Nields' assessment, committee members have so far focused "on whether the government functioned properly."

He also says, "My judgments are not the ones that matter here ... It does change my job as a lawyer fairly dramatically. Usually I'm the one who's deciding what I want to go out and prove."

Despite the publicity, he says he's only gotten a few calls at home, most of them easily fielded by his teen-age daughters. His number is still in the telephone book.

"I don't like unlisted numbers," Nields says. "They're like locks on your doors, locks on your car, and security systems and metal detectors and all those other things that make life unpleasant."

It's Sunday and John Nields is working in his makeshift office on the House side of the Capitol. On the top floor known as the attic, it's cloistered and guarded -- a uniformed security man sits outside the entrance and a special ceiling light goes on when uncleared visitors are present. Otherwise it's a welter of bookcases, desks and stacks of boxes that House staff counsel Pat Carome calls "organized chaos."

Nields' desk is in the back, facing a line of bookcases, the "Secord-Hakim Organization Chart" propped against a bottom shelf. On a more prominent shelf is a large color photo of Nields with his wife and three daughters, smiling at the top of Giant Mountain in the Adirondacks, where he's been going for vacations since he was a boy and where he expects to go as soon as the hearings end. He stumbles over the ages of his daughters: "They've changed ages while I've been in this crypt," he grumbles good-naturedly.

Staff members come and go wearing shorts. Someone's dog pads quietly through the room, looking to nuzzle.

Nields' forehead bears a hint of tan from the previous day's tennis -- his first day off since the hearings began, he says. He's at this office almost every day, often at 7 a.m., and is rarely home before 10:30 p.m. During an extended break in the hearings last month, he flew to Atlanta to deliver oral arguments in two different cases he has been handling at Howrey and Simon.

He'll concede that the hearings have, in a way, enslaved him. "But I don't really want to be," he says. "I like to play. I'm a little compulsive about my work, but don't say I'm a workaholic, okay?"

The television image of him as tough and humorless perplexes those who know him best. "He's twinkling," says his younger sister, Jenifer Nields, a psychiatrist, "full of mischief."

He likes to play guitar and sing folk songs with his family. And for the last five years, he's been singing and dancing in an annual Christmas pageant, the Washington Revels, held at Lisner Auditorium. "I like to sing and be part of a group. It's different from performing solo as a lawyer."

John and Gail Nields have a tennis court at their McLean home -- and were once ranked as the top husband-and-wife doubles team in the country (a now defunct category) "without ever having won a tournament," Nields says laughing. "I think it was because all the other couples broke up and we stayed together," he quipped.

They have three daughters: Nerissa, 20, a junior at Yale, Katryna, 18, who will be entering Trinity in the fall, and Abigail, 13, an eighth-grader at the Potomac School in McLean. All were at the hearings on the opening day of North's testimony.

He grew up in New York City, one of four children, a graduate of Andover, Yale College and the University of Pennsylvania Law School. His father, now deceased, was a lawyer who gave up his practice to teach at Sarah Lawrence College; his mother is an active board member of the Goddard-Riverside Community Center in New York and a former trustee of Bennington College -- her mother was one of the founders of Bennington.

"I think I just backed into law school," he says, crediting his interest in law to his father. He and Gail were married when he was 20, entering his senior year, and she was 19, beginning her sophomore year at Connecticut College. "Our younger sisters were good friends and they introduced us when they felt the time had come," Nields says, laughing. Among their common interests was baseball -- in particular the former New York Giants.

"We really were good for each other when we were together," says Gail Nields, 43, a history and government teacher at the Potomac School, who graduated from the University of Pennsylvania while her husband was in law school. "In fact we both did better academically when we were together."

After law school he spent two years as an associate at a New York firm, Davis Polk & Wardwell, then left -- "probably the biggest decision I made as a lawyer" -- to become an assistant U.S. attorney for the southern district of New York, which includes Manhattan.

"It's the most rewarding job a young lawyer can have," Nields says. "I always had the feeling that we were on the right side. If we made mistakes, we'd fix them."

He stayed for five years, including a year as chief appellate attorney, supervising and trouble-shooting for other lawyers in the office.

Around that time, Supreme Court Justice Byron White was looking for an experienced lawyer to clerk for him; Nields was recommended for the position, which he kept for three years until 1977. "I always thought I would do government service for about five years and then grow up and be an adult like everyone else and go into private practice," Nields says. It didn't quite work like that.

During the time he served as chief counsel to the congressional Korean influence investigation in 1977, he met Rep. Lee Hamilton (D-Ind.), who would later ask him to serve as counsel to the Iran-contra investigation.

After Koreagate, Nields joined Howrey and Simon -- but was quickly asked by the Justice Department to lead the prosecution of FBI officials Felt and Miller. For much of the 20 months that he worked on the case, Nields was not even sure if the two should be prosecuted. (Felt and Miller were convicted, and President Reagan pardoned them, an action that Nields criticized.)

But eventually, Nields says, "I came to believe very strongly that the underlying constitutional issues had to be tried."

Television has, in some ways, reduced the hearings to a sampling of personal behavior, and Nields is not without his quirks. After hours of watching him, obsessed viewers began to detect and catalogue his mannerisms -- the roll of his eyes, the flick of his head. And they fastened on his long hair, which appears a violation of the Washington lawyer dress code that he otherwise embraces.

"I must say this is not something at the uppermost of my consciousness," he says with a grin, lifting a hand to smooth over a lock, "but if you keep mentioning it, it will be."

"He's not an image kind of person," says Gail Nields. "He wouldn't make a statement with how he looked or what he wore."

Nields himself has not watched tapes of his own television performance. "Maybe I should have," he says with a rueful laugh.

Some thoughts from those who have watched him:

"Well, as far as I'm concerned, John Nields and the Senate counsel have done what they were supposed to do -- make a record, and it's an excellent record," says Rep. Dante Fascell (D-Fla.). "This is not a beauty contest."

Rep. Jim Courter (R-N.J.) has complained that both Nields and Senate chief counsel Arthur Liman have been exceeding their charge -- to lay out the framework of events so that members of Congress can probe policy, credibility and motivation. "The lawyers are doing everything and the members are making speeches," Courter said. "All the tough questions, all the areas have been covered."

"I think he had a very difficult assignment in connection with questioning Oliver North," said Ben-Veniste, who has done some television commentary on the hearings. "There had been no substantive questioning beforehand and there were a number of things to establish."

Gail Nields says, "I don't think he was being confrontational at all. To the extent that Oliver North wasn't answering the question, he would repeat the question until he got the answer. But he does that with me, too."

Some observers say that the lawyer who appears to fare better depends on the order of the questioning: Whoever goes first must elicit the facts and chronology while the second lawyer can essentially "cross-examine" and in the process look more incisive.

Nields agrees that the roles change. "I think the first lawyer has more of an obligation to cover the waterfront. The second lawyer can hone in," he says.

"I think as far as my job is concerned," Nields says, "the most important thing is finding and presenting the information and being reasonably confident we're presenting what we're supposed to be."

Hatch predicted that the lawyers' roles would be played down as the hearings swing into the homestretch. "You're going to see a lot more politics," Hatch said. "And you'll see a lot of Meese-bashing incidents. Since they can't get the president on diversion of funds you'll see them going after Meese."

Nields sees his career unfolding as a mix of the government and private work that it has already been.

"He would very much like to be a federal judge," his wife says, "or a teacher."

In fact, Nields says he had some discussions a couple of years ago with Harvard Law School about teaching there but he decided for the time being not to pursue it. "I have a keen interest in the intellectual aspects of the law," he says.

He grimaces. "And I wouldn't mind having a little more control over my time."