Ms. Bigelow received the story from the screenwriter Mark Boal at a time when its power, importance and necessity could not be ignored: A grand jury had just declined to indict a white police officer in the killing of Michael Brown, an unarmed African-American teenager, in Ferguson, Mo., in 2014.

“It was two things simultaneously,” Ms. Bigelow, 65, said of her initial reaction. “One is kind of a, ‘I’m white, am I the right person to do it?’ And the other is an extremely emotional reaction to the constant recurring of these events.”

She realized, she added, “that I have this opportunity to expose this story in the hope that maybe it either generates a conversation, begins to generate a conversation and/or encourages more stories like this to come forward. To do nothing was not an answer.”

If the time is right for this movie, opening wide on Friday, Aug. 4, after a limited release, it is also daring. Detroiters, coming out of the nation’s largest municipal bankruptcy, are touchy over how their city’s narratives are told, whether it be the jaded tales of blight or the glowing renaissance stories that somehow overlook those in the black majority being left behind. And more broadly, we are in a moment of heightened scrutiny over how black Americans are treated by the police and how they are portrayed in films, books and news coverage.

The reality of two Americas means that there is a significant segment of the population for whom the idea of racism in policing is either difficult to grasp or fiction. That makes the telling of this story by someone like Ms. Bigelow vitally important, said Michael Eric Dyson, the scholar and activist. Her broad appeal can attract white viewers who might not otherwise go to see a movie about this topic, he said.