Next weekend, the award-winning filmmaker Alex Gibney will see the long-awaited theatrical release of his torture documentary, “Taxi to the Dark Side,” as well as the premiere of “Gonzo: The Life & Work of Dr. Hunter S. Thompson,” at the Sundance Film Festival. Two very different films, but as Mr. Gibney recently discussed his chronicle of an Afghan taxi driver’s brutal death at Bagram Air Base, he felt a resonance with the ghost of Thompson.

“What made Hunter interesting is that he embodied, in his own psyche, this schism in the U.S. between a sense of idealism and what he called ‘fear and loathing’ — our dark side,” Mr. Gibney said. The “dark side” is on Mr. Gibney’s mind and prominent in the title of his new torture documentary, which references Vice President Cheney’s statement soon after September 11, 2001, about using “any means at our disposal” in anti-terrorism intelligence efforts. In “Taxi to the Dark Side,” Mr. Gibney cogently traces the ensuing institution and proliferation of the administration’s “enhanced interrogation techniques,” framing the account with the fate of the innocent cabbie, Dilawar. “The momentum of torture haunted me,” Mr. Gibney said. “The soldiers concluded on day three of the five-day interrogation that he was innocent, but tortured him for another two days.”

The film, which is guided by the director’s measured voice-over, finds its heart in its interviews with interrogators and MP’s involved in such interrogations. (Dilawar’s family, as well as the legal scholar and former administration official John Yoo and others also appear.) Mr. Gibney discovered that the soldiers didn’t believe they were innocent but did feel scapegoated. The young men were also clearly scarred by their experiences.

“You can see they are containing themselves because, if they let themselves go, you’d see a torrent of emotion,” he said. “It’s not oversentimentalized, but they feel haunted.”

But besides what appears onscreen, Mr. Gibney’s background understanding of the torture phenomenon rises beyond self-hating wallow or even a barbed critique such as last summer’s Iraq postmortem, “No End in Sight” (which he also produced). Tellingly, after Mr. Gibney’s 2005 breakthrough, “Enron: The Smartest Guys in the Room,” the veteran of television productions directed a film partly about the Milgram obedience experiments of the 1960s, “Human Behavior Experiments.”

In the infamous project, subjects were ordered to dial a switch that they were told would cause a stranger in the next room to be shocked electrically — first a little, then a lot …

“Sixty-five percent of the people ended up pushing the lever to the point where they would have shocked somebody to death if there really had been somebody on the other side,” Mr. Gibney said. “But 35% refused to take part. We’re inclined to obey, but not hardwired. A kind of spiritual corruption takes place that I think is a good metaphor for what happens with torture and the torturers.”

Abu Ghraib was featured in “Human Behavior Experiments,” and after the 2004 scandal, Mr. Gibney was amazed at the national response (“I think it is worth a film in itself,” he said). But he believes the Bush administration successfully marginalized the incident at the time.

In his new film, he justifies an instance of re-enactment partly because the administration has since tightly controlled images from interrogations. “We visualize the interrogation of Mohamed Qahtani and juxtapose it with actual quotes from the logs relating to those interrogations,” Mr. Gibney said. “As a filmmaker, that’s one’s only defense.”

“Taxi to the Dark Side” even faced initial opposition from the Motion Picture Association of America over a poster featuring a small photo of a hooded prisoner — a photo from a camera originally confiscated by the American military. Abu Ghraib also spurred Mr. Gibney to talk about the issue of interrogation with his father, a Navy veteran who questioned high-level Japanese prisoners in World War II. Frank Gibney, an accomplished journalist who passed away last year, appears briefly, but forcefully, in the film. “It really got under his skin,” Mr. Gibney said. “Like many people of his generation, the experience of World War II was very, very important. He’d written a book about Okinawa, and a prisoner he interrogated, and we’d worked together on [the 1992 TV documentary] ‘The Pacific Century.'”

His father’s participation changed the presentation of the film: “Only when I decided to put my dad in the film did it become personal enough to put my own voice-over.”

The sensitive subject matter in “Taxi to the Dark Side,” which was voted Best Documentary at last year’s Tribeca Film Festival, now awaits the unpredictable reactions of mainstream audiences. As he faces the fray ahead, Mr. Gibney, a prolific producer besides creating his own films, has come to appreciate the “distance and discipline” afforded a project’s producer.

Asked whether he prefers producing or directing, he mused: “It’s a funny thing because when I first started out, nobody referred to a documentary filmmaker as a ‘director.’ What was it that Hitchcock once said? ‘On a fiction film set, the director is God. On the documentary set, God is the director.'”