Director Alex Gibney introduces No Stone Unturned as an unfinished investigation, as well as a potent symbol of how individual justice becomes lost during a war of terrorism, sacrificed for the greater good of reconciliation rather than for truth. His examination uncovers a level of government impunity that should substantively change how law enforcement works with intelligence services, though the implications of broader applicability get lost here.

His Ceasefire Massacre (2014), an episode in ESPN’s 30 for 30: Soccer Stories, started as one of those “feel good” sports-can-make-the-real-world-better stories. On June 18, 1994, New Jersey’s Giants Stadium hosted a Cinderella team, the united Irish World Cup team (that had earned its berth in Northern Ireland) vs. favored Italy, competing before an ecstatic international audience of politicians, businessmen, and kiss-me-I’m-Irish fans. During this time, peace talks were starting between Catholics and Protestants who had been in a civil war during the bloody decades known as the Troubles. But while the stadium was still cheering Ireland’s victory, in the rural Northern Ireland town of Loughinisland, two masked men entered the Heights Pub, fired assault rifles, killing six Catholic men, wounding five. No one was charged with the murders, though suspicions pointed to the Ulster Volunteer Force, the violent pro-British Protestant militia.

By fall, attention had shifted to the peace process, when first the Irish Republican Army and then the Protestant paramilitary forces declared a ceasefire. Four years later, the Good Friday Agreement led to the full political solution in 2006, as depicted earlier this year in the feature film The Journey. Throughout these tenuous negotiations, the police and the British government discouraged the demands for justice by the survivors and victims’ families. Gibney’s team had conducted an investigation for the short film, but they didn’t feel they had served the grieving and angry families adequately. Meanwhile, local independent investigators had been uncovering new evidence.

Much of this documentary is about—and in the style of—forensic analysis familiar from reality crime TV shows. What makes this film significant is just how much evidence there was available within days and weeks of the killings that was either not thoroughly examined or the results never reviewed, especially the getaway car left in a farmer’s field and a bag with the gloves, handguns, and masks worn by the killers. Through interviews with former terrorists, determined journalists, officers of the Royal Ulster Constabulary and other government officials, more questions and coincidences raise questions about who was protecting confidential informers, and even the perpetrators.

What makes the film, and Gibney’s investigation, possible was the establishment in 2000 of the police ombudsman for Northern Ireland to provide an independent, impartial system to review complaints of past police actions. The ombudsman took up “The Loughinisland Massacre,” and Gibney interviews the investigators and follows the clues for what hadn’t been made public. (The fictional Shadow Dancer turns out to have a lot of truthful resonance on government complicity, though that was told from the IRA’s side.)

Visually, that means the film constantly returns to blown-up sentences in the report, which is a repetitive device, and the emphasis on individual names becomes overwhelming to track. More cinematic is when Gibney’s hired private investigator learns where a prime suspect is now located, and he’s seen on hidden video going about his business with his wife. Cameras are also there when the tearful families are vindicated by receiving the final, detailed report from the ombudsman pointing at shocking collusion between the police and the terrorists and how far the cover-up went. The specific accusations are so incendiary that there are still challenges and litigation.

Gibney chooses to end the film with the families’ emotional responses, but there could also have been philosophical or practical discussions about how British law enforcement and intelligence services should have dealt with terrorist sympathizers in their ranks. The experiences of the more than 40 Truth and Reconciliation Commissions around the world could also be relevant. Any government these days may have to deal with conflicted frontline officers who may feel loyalty to informers or opportunistically sympathize more with criminals or terrorists than with the politics of shifting public policy.