Alex Gibney's Oscar-nominated documentary Taxi to the Dark Side is so disturbing, on so many levels, that it's hard to know where to begin.

By examining the 2002 homicide of an innocent man - an Afghan taxi driver named Dilawar who died in custody at the U.S. Air Force base prison in Bagram, Afghanistan - the film makes the case that in the post-9/11 "War on Terror" world of President Bush, Vice President Cheney and former Secretary of Defense Donald Rumsfeld and former Attorney General Alberto Gonzales, many of the fundamental rights and beliefs represented in the U.S. Constitution have been undermined, subverted or altogether jettisoned.

Gibney's previous film, Enron: The Smartest Guys in the Room, offered a devastating indictment of corporate greed. In Taxi, a different kind of corruption is at work: Using interviews with military police officers involved in the four-day-long beatings of Dilawar that led to his death, the film argues that the abuses at Bagram (where scores of homicides have been reported), and at the infamous Abu Ghraib military prison in Iraq, are not the work of a "few bad apples," as Bush administration figures insist. They are the direct result of the White House's decision to ignore the rules of imprisonment and interrogation laid out in the Geneva Convention.

Waterboarding, sensory deprivation, sexual humiliation, auditory assaults - taken separately, these techniques may not technically fall under the definition of torture. But look at the images from Bagram and Abu Ghraib in Gibney's picture, and listen to the soldiers who dealt hands-on with the detainees, to experts from the FBI, to lawyers and professors, to Sen. Carl Levin, chairman of the Senate Armed Services committee, and to Lawrence Wilkerson, former chief of staff for Colin Powell.

It becomes clear what Vice President Cheney meant when he told Meet the Press' Tim Russert that after the attacks of Sept. 11, 2001, it was necessary to go over to "the dark side. . . . It's going to be vital for us to use any means at our disposal, basically, to achieve our objective."

But what is that objective? Ask Moazzam Begg, a British citizen who was detained for two years at Bagram and Guantanamo as a suspected "enemy combatant" before finally gaining release after his government intervened. In the film, Begg suggests that because of the wrongful imprisonment, harsh treatment and absence of legal recourse he and others were subject to, Guantanamo isn't so much a terrorist holding facility, it's a terrorist factory, a breeding ground for fervent anti-American sentiment.

That's the dark side.

Taxi to the Dark Side ***1/2 (out of four stars)

Directed by Alex Gibney. With President Bush, Moazzam Begg, Willie Brand, Damien Corsetti, Carl Levin, Alberto Mora, Lawrence Wilkerson, John Yoo and others. Distributed by ThinkFilm.

Running time: 1 hour, 46 mins.

Parent's guide: R (images of torture, nudity and sexual humiliation, adult themes)

Playing at: Ritz FiveEndText