Pamela Yates has carved out a career as a photographer, documentary filmmaker, and editor over the past 30 years and Granito: How to Nail a Dictator brings her work full circle in a way. Yates’ 1982 documentary on Guatemala, When the Mountains Tremble, became forensic evidence in a genocide trial against the military dictator. Yates had been allowed to shoot the only known footage of the army as it carried out its genocide. Now, 25 years later, this footage is evidence in an international war crimes case against the commander who allowed Yates to film. A “granito” translates as a tiny grain of sand and those are the threads that must be sifted to find the “truth.” Granito was the opening night film for the Film Society of Lincoln Center’s annual Human Rights Watch Festival.