Alex Gibney, the non-fiction filmmaker who won the documentary feature Oscar last year for “Taxi to the Dark Side,” is back with a picture called “Gonzo: The Life and Work of Dr. Hunter S. Thompson,” profiling the unorthodox Rolling Stone journalist who wrote “Fear and Loathing in Vegas” and “Fear and Loathing on the Campaign Trail,” served as the model for Doonesbury’s Duke and finally committed suicide in 2005. He came to Dallas for a screening of it at the AFI Film Festival.

“I didn’t know him as a person, but I certainly knew his writing,” Gibney said during an interview. “I had been a big fan of the two big books, but I hadn’t been a Thompson completist. It wasn’t like I’d read everything that he’d written. And I’d been reading and thinking about him after he died. But I didn’t really think about making a movie about him—that wasn’t one I was beating my breast to do.

“But then I was approached to do it, and I thought it would be pretty interesting, in part because one of the things that interested me about him was that he broke the rules of traditional journalism in ways that were helpful, because sometimes people in power, particularly politicians, tend to use the rules against journalists to some extent,…using the ‘fair and balanced’ standard, which is fine—everybody should go out of their way to see all sides of the story. But if you discover, in your judgment, that something is the truth, you shouldn’t have to balance the truth with a phony opposition. So those things about Hunter interested me.”

Gibney recalled that his inclination to take on the project was spurred further by a column in the New York Times by Frank Rich about Dan Rather (then being dismissed by CBS), Thompson, and the notorious plant Jeff Gannon. “At a time when the White House is hiring actors to impersonate journalists,” he paraphrased Rich, “we need somebody who doesn’t play by the rules.

“I don’t think it’s for everybody, and I don’t think everybody should do it. But I think that what was great about Hunter was that he subverted the rules in ways that were useful. It’s like what Franz Mankiewicz, McGovern’s campaign manager, said about him—he said that his campaign writings were the least factual and most accurate record of the campaign. And I think that’s pretty good.”

Once Gibney said yes to the project, he had to hit the ground running. “My very first assignment was to go to the funeral,” he said. And then he went to work with the archives, which Thompson had left in the charge of his biographer Douglas Brinkley. “The estate was very generous in terms of giving us access. We got a lot of stuff that nobody had ever seen before. But it was not well catalogued. We found the tape of [Jimmy] Carter giving the Law Day Speech [in Georgia]”—the basis for a long article by Thompson that gave the governor his first national recognition—“in the bottom of a box. It was barely marked, it just said ‘Carter.’” And it—along with an interview with Carter—became a major episode in “Gonzo.”

In other cases, though, Gibney had to search well beyond the archives. “Somebody had tipped me off that he had been on ‘To Tell the Truth.’ And I talked to his wife about it, and she told me the story. And I thought, ‘Wow, wouldn’t it be great to get that?’ We actually found it in Australia, believe it or not. Somebody owns all those episodes. But even so it took us a long time to find that one. We finally got it, and it’s just fantastic—he’s not the sort of larger-than-life character that he became later.”

Gibney also scored interviews not only with family, friends and colleagues, but with people Thompson had covered like McGovern and Carter. Even Pat Buchanan, who’d worked for Nixon (whom Thompson had savaged), agreed to sit for an interview after some initial reluctance. Gibney attributed their readiness to Thompson himself. “Hunter was one of those people who reached out to everybody. He did what a good reporter does, which is to try to understand what everybody’s thinking. He hated Nixon, but he really wanted to make a point of riding in a limo with him, and they talked football for an hour and a half. That’s what I mean about Hunter. He played fast and loose in some ways, but he was a very good reporter in other ways, because he was always trying to get people who didn’t necessarily agree with him to talk to him.”

Gibney also succeeded in securing the participation of the one celebrity he considered essential—Johnny Depp, who played Thompson in Terry Gilliam’s “Fear and Loathing in Las Vegas.”

“He narrates every word in the film,” Gibney said. “Every word is Hunter’s, but we culled those words in order to be able to tell his life story. I think getting Johnny was key, not because he’s a celebrity but because Johnny is a real student of his work, and had inhabited him—he’s the guy who went and lived at Hunter’s house for however many weeks when he was preparing for the ‘Vegas’ role, and really feels a deep connection with him. So in some way he became Hunter—what better person to read [the script]? We waited a long time for Johnny, and I think it was worth the wait. We were pretty determined that he be the voice.”

Gibney, finally, connected Thompson with his own field of endeavor. “Documentarians have learned, like Hunter, to toss out the old rule book and to use all sorts of techniques that were formerly only available to fiction filmmakers.

“And I think that’s great.”