The subject the mistreatment of prisoners taken by American forces during the Bush Administration’s so-called war on terror has received a good deal of attention in the media, but this documentary by Alex Gibney (“Enron: The Smartest Guys in the Room”) approaches it from a personal perspective that gives it special power and poignancy. “Taxi to the Dark Side” uses as its point of departure the fate of Dilawar, an Afghan taxi driver who was taken into custody in 2002 by American forces in connection with a rocket attack and brought to Bagram Air Force Base, where he died within a week, the cause of death later listed as a homicide.

That case gives Gibney a jumping-off point for a broader analysis about how U.S. interrogation policies were developed by politically-driven operatives in Washington and put into practice by largely untrained personnel—a treatment that includes interviews with officials and journalists, but also with soldiers who actually served as interrogators at Bagram and were charged and tried for their actions there (as opposed to the higher-ups who have escaped punishment) and with ex-prisoners themselves.

But the film always returns to Dilawar’s fate to give the wider story a particular tragic dimension. The recreation of his case is at once sobering and infuriating, and the footage of his family is wrenching, quietly but compellingly showing that the policies the film depicts unwittingly sabotage the very goals they’re meant to achieve.

The film is expertly shot and edited, making its points with authority but without becoming strident or dunning. It’s eloquently capped by footage of Gibney’s late father over the final credits—a former Naval interrogator so furious over what he viewed as the perversion of his former profession that he urged his son to make a film about it. That gives a second highly personal aspect to “Taxi to the Dark Side,” which probably explains why it’s such a moving piece of work.