In the disturbing yet vital film Taxi to the Dark Side, Army Specialist Damien Corsetti, one of six interrogators who confessed to torturing and killing an innocent taxi driver at the Bagram Air Force Base in Afghanistan in 2002, stoically peers into the camera and tries to justify his actions.

“When you look at people as less than human, you find yourself doing unthinkable things,” Mr. Corsetti says of his role in the death of Dilawar, the young Afghani wrongly accused of being the trigger man in a rocket attack.

This statement aptly sums up the themes of filmmaker Alex Gibney’s meticulously crafted documentary. Winner of this year’s Academy Award for best documentary feature, Taxi to the Dark Side will be screened Sunday as part of the Martha’s Vineyard Film Festival.

This is not so much a film about the horrible things people are forced to do during war, as about the horrible things soldiers readily accepted as part of war. As one solider in the film puts it, the circumstances of the U.S. invasion of Afghanistan, in the wake of the Sept. 11 terrorists attacks, led soldiers to “lose their moral bearings.”

The film is loosely structured around the death of Dilawar, who was brought in December 2002 to Bagram, a former Soviet air base converted into an interrogation site for suspected Taliban operatives. Less than a week later, he was found dead in his cell; military officials listed the cause of death as natural causes.

However a pair of New York Times reporters, Tim Golden and Carlotta Gall, investigated further. They tracked down Dilawar’s family as well as a U.S. death certificate which listed the cause of death as homicide.

The film uses Dilawar’s death to put a human face on torture, explaining how he was chained to the ceiling of his cell and subjected to a practice called “knee strikes” to the point where his legs had become pulpified; they would have to have been amputated had he lived.

Dilawar’s case becomes the springboard to a larger indictment of sanctioned and unsanctioned torture by U.S. forces in the war on terror.

The documentary goes on to chronicle abuse at Abu Ghraib, Bagram prison and Guantanamo Bay. Common practices include forced standing, sleep deprivation, sexual humiliation, forced nudity, the threat of dog attacks, and waterboarding, forcing a victim to inhale water to simulate drowning.

But perhaps the most disturbing aspect of these barbaric tactics is just how readily soliders embraced them as a matter of duty — raising few quibbles about the morals or ethics of their actions.

Mr. Gibney wrote and directed the equally compelling documentary Enron: The Smartest Guys in the Room. In Taxi, he uses interviews with five soldiers who were eventually found guilty for Dilawar’s torture and death, to show how U.S. soldiers were operating under poorly defined directives, with minimal input from their superiors, about the use of physical and psychological brutality on prisoners.

And while the soldiers interviewed for the film seem haunted by their actions after the fact, each concedes that at the time, they accepted their orders as a matter of course. Many of the soldiers even admit that they believed the taxi driver, who weighed no more than 120 pounds and offered no resistance, probably had done nothing wrong.

But as one soldier puts it, “I didn’t want to be seen as going against my fellow soldiers” by questioning the use of torture.

After Sept. 11, 2001, U.S. leaders suddenly embraced aggressive interrogation as a means to gather information. The “dark side” in the film’s title is taken from a quote by U.S. Vice President Dick Cheney in the days following those attacks.

“We will have to work the dark side, if you will,” Mr. Cheney said on Meet the Press. “We’re going to have to spend time in the shadows.”

Taxi to the Dark Side lays out — through documents, television clips and interviews with military leaders — how this embrace of the dark side by U.S. leaders has led to a global campaign of kidnapping, torture, illegal detentions and shaky evidence gathered through torture. No one who views Taxi To the Dark Side can plead ignorance to disturbing erosions of basic human morality which have been committed in the name of protecting the American way of life. One of the most shocking revelations in the film is the introduction of a bill to Congress that would effectively pardon members of the Bush administration from future prosecution for the use of torture and abuse.

“Richard Nixon at least hired Gerald Ford to do the pardoning,” Mr. Gibney, who narrates the film, says in a voice-over.

The film makes a compelling argument that the vast majority of the soldiers detained at places such as Guantanamo and Bagram are likely innocent of any acts of terrorism. As of September of 2006, the film states, none of the 83,000 people incarcerated in the name of stopping terrorism had appeared in court to defend themselves.

Only seven per cent of those detained at Guantanamo were even captured by U.S. soldiers; over 90 per cent were taken by Iraqi or Afghani personnel. Indeed the men who captured Dilawar and turned him over to U.S. forces seem to have done so, according to the film, simply to collect what amounts to a cash bounty, offering no evidence that he was guilty of any terrorist attacks or associations.

The movie comes full circle when Mr. Gibney shows scenes of his father, Frank Gibney, a Naval intelligence officer during World War II who was terminally ill in the hospital while he was making the film. The senior Gibney explains that he and his fellow soldiers never considered using torture on Japanese soldiers during the war — not so much because it was morally wrong, which they knew it was, but because they knew doing so would bring them to a dark side they believed they were fighting against.

“We thought our principles gave us a strength the enemy didn’t have,” Frank Gibney recalls in the closing minutes of the film. “It’s what made us different.”

Taxi to the Dark Side screens at 5 p.m. Sunday at the Chilmark Community Center. Tickets are available at the door.