The fourth season of "Picket Fences" has proved to be both pivotal and controversial - oddly enough, because the show has proved to be somewhat less controversial than in years past.

And at the center of the current upheaval is executive producer Jeff Melvoin.In the spring of 1995, creator and former executive producer David E. Kelley called it quits. The man who had guided "Fences" through its first three seasons and wrote - or rewrote - most of its episodes turned the reigns over to Melvoin, who had served as executive producer of shows like "Northern Exposure" and "Hill Street Blues."

"When I first met with David about the show, he was so beat up by the workload he'd had," Melvoin said. "He said, `I'm out of issues. I don't know where you can keep going with these things.' "

Thus, the decision was made to step away from the issues-oriented episodes that had been a "Picket Fences" trademark and concentrate more on character development. It was a decision that was endorsed by Kelley, the studio and the network.

"We talked about giving the show a new emphasis in the early part of the season," Melvoin said. "I had mentioned that with my background, particularly with `Northern,' that I would be interested in seeing what we could do exploring the characters a little bit and backing off of the court (scenes) initially. I said if that was of interest to them, then that was fine. If it wasn't of interest to them, then I probably wasn't the right person for the job.

"They made it very clear that they felt that was right in keeping with where the show might go. . . . That the hallmarks weren't so much the courtroom or the social issues as much as the quality writing, unpredictability and a willingness to take on areas and not to flinch."

It was a tough task - trying to fix a show that wasn't really broken, but at the same time a show that was "critically acclaimed but had never been a significant popular success," as Melvoin accurately termed it.

But the ratings dipped and the second-guessing began - despite the fact that much of the audience loss could be attributed to the fact that CBS moved the show up an hour from 9 p.m. to 8 p.m. on Fridays. And the new president of CBS Entertainment, Leslie Moonves, has hardly endorsed Melvoin and his efforts.

"Clearly, when you remove David Kelley . . . you will never get the same type of quality week in and week out," Moonves said. "To say that the show is different would be accurate. Jeff Melvoin is a very good producer. He's not David Kelley, but then again, there aren't many of them.

"Has the tone of the show changed? Yes. Is it better? I'm not sure."

And asked directly if he liked the show now, Moonves simply replied, "No comment."

There's been some grumbling among cast members as well.

"I don't know whether it's as good as it was or not," said Ray Walston, who stars as Judge Bone. "Obviously the show is different without Kelley. . . . I just feel it's a different show in a lot of respects, and that was the way that they wanted to go. They wanted to take a fresh look at things.

"They thought that maybe there'd been too much courtroom stuff. Maybe there'd been too much religious stuff. I disagreed with that, however. But I'm not one of the 18 or 19 or 30 producers over there. You know, you can't fight that army."

Walston is, of course, exaggerating a bit. But hiking from Stage 6, where much of the series is shot, to the old Writers' Building on the Fox backlot does give you an entirely different perspective.

The building is old, and currently under renovation. Melvoin's office is large, white and bright, but the air conditioning system is loud and annoying and the place shows its age.

Studio lore holds that the space was once part of Shirley Temple's classroom.

And there's no bunker mentality in this office for 42-year-old Melvoin, a former writer for Time magazine. He's welcoming, open and honest, and not defensive in spite of the fact that the previous week TV Guide had called Melvoin and his staff "insane" for making the changes that had "ruined" the show.

"I've never regretted the decision to do it," Melvoin said. "I'm surprised it took so long for an article like that to appear. . . . You know, fools rush in. I thought it was a challenge worth taking."

The challenge was not small, however. And, while you can argue whether the quality of "Picket Fences" dropped off as the fourth season began, you cannot argue the fact that the show did indeed leave the courtroom largely behind and - just as Melvoin promised - look more at the characters.

"There are certain people - longtime fans of the show - who did feel abandoned. They felt that the show had perhaps departed from what had made it so distinguished," Melvoin said. "I respectfully disagree. Given a little bit of perspective, I felt that the writing quality was every bit as high. I felt that the characters were every bit as pronounced, but we were putting the focus on more human issues and not so much social interaction between the players. And filling out their histories and personalities a little bit more.

"And, frankly, I felt that that was a comfortable way for me to get into this situation. To kind of get under the hood and see how the show worked. And as I felt more comfortable with that, we were able to take it back toward the court a bit and back into what I consider some of the more headline-oriented issues."

Indeed. In recent weeks, "Picket Fences" has again taken on some tough issues, from having the Pope testify in a murder trial to putting a Jew on trial for the murder of a Nazi some five decades earlier, from animal rights to teen suicide.

Melvoin defends himself, his staff and the early episodes of the current season, but at the same time he readily admits that both he and the other writers have learned as they've gone along. In November, they met for some "mid-course corrections" - not an abandonment of their earlier efforts, but perhaps a refinement.

"I tried to bring a little bit of Cicely, Alaska, to Rome, Wisconsin, and Rome, Wisconsin, was talking back to me a little bit and saying, `We're not Cicely,' " said Melvoin, referring back to "Northern Exposure." "I feel much more secure about Rome, Wisconsin, now.

"And I feel that Cicely was a place where you wanted to be. Where those characters and that environment made you feel completely at home. Rome is a different place, and it's taken me a while to kind of get underneath it a bit and understand that . . . Rome is a darker place. When you peel back the layers of Rome, it's not all great. There's a lot of things revealed that mirror problems in our society. And the trick is how to keep our characters heroic and at the same time identifiable. And keep the show something worth watching, recognizing that perhaps our lead characters are the ones keeping that town from, so to speak, eating itself. Feeding on itself.

"It's taken me a while to appreciate that. It's become a real place to me now. Much as longtime viewers have felt, I feel I know that place."

And, qualitatively at least, the show has show marked improvement in recent weeks. It's as if it has struck more of a balance between the character development and those controversial issues the show has explored.

"I think there was an impression that we had abandoned that side of it," Melvoin said. "And it really wasn't so much that we'd abandoned it as it was a question of where to put the initial emphasis. That on a dynamic range, I felt that the show had put a lot of emphasis on the court, on the social issues, and was in danger of getting a bit formulaic.

"I thought, on the other hand, that there was all this territory that had not been explored. And I thought it would be great fun, as a writer and the head of a writing staff, to explore that and see what happened. And I'm very proud of the initial episodes that we did."

All of this comes to a man who already has plenty on his plate. On this day in mid-January, he's working on another revision of next week's script. He's dealing with notes from the network - including a note from Programs and Practices to remove a reference to the brand-name Coke from a script.

He's talking to the show's legal adviser about an upcoming episode. He's talking to series star Kathy Baker about some of her concerns with a script. He's revising the script of one episode while checking the dub of another.

He and his staff have a conversation about still another script, looking for a way to resolve the story. Two more scripts are in the works at the moment.

There's a scoring session for an episode. There's editing. There's looking at dailies. There's a conversation with a director about whether to make the basketball team that's part of an upcoming episode co-ed.

There's the discovery that "completely inadvertantly," co-star Kelly Connell had been left out of two consecutive episodes.

Still, Melvoin finds time to coach this sons' soccer team and serve on their school board.

"Soccer is kind of the great gateway to getting out of here. It's kind of my life preserver," he said. "So once a week, during the fall, I get out of here by 4 o'clock. . . . And I have a very understanding wife."

And, amidst some worry about whether the network will renew "Picket Fences" for next season, Melvoin is optimistic. He was co-executive producer of "Hill Street Blues" in its final season, and he doesn't see the fourth season of "Picket Fences" as the end.

"I know what it's like to take the Graf Spee out and scuttle it in Montevideo Bay. It was no fun to just guide that thing to its death," he said. "Whereas in this case . . . I felt there was a real opportunity to - not exactly reinvent the show, because it didn't need it - but to inject it with a new spirit and kind of make it almost the pilot season it all over again. Saying, `We're going to take this diamond that we've been looking at from this perspective and tilt it and look at it from this perspective for a while.'

"And that's the only reason I took this job - because of that excitement."