Yance Ford presents this documentary as if it were an art film. Of course, all documentaries, indeed all films, are to some extent "art films", but documentaries often rely on a straightforward offering of facts. There are "facts" in Strong Island, but Ford's use of unusual transitions (fading into and out of black in order to shorten lengthy interviews) and the specificity of his camera shots (Ford's mother, a key interviewee, almost always appears in medium shot, while interviews with Ford show him in extreme close-up) work to direct us away from the narrative. Ford has a story to tell, but he seems more interested in the arc of the lives of the characters than he is with giving us "what really happened".
This is not a Rashomon-style film, with multiple perspectives describing the same event from different perspectives. Ford wants to show emotional realities, and when the various people tell their stories, he shows how events change their lives. Strong Island is about the murder of Ford's brother, but there is no recreation of that event, and only a few times do we even get details about the murder. Whenever we do get details, the purpose isn't to explain the crime, but rather to demonstrate how it affects the people who lived, family, friends, all of whom have their lives changed by the murder. Everyone at some point blames themselves, trying to figure out what they might have done differently to prevent the situation that resulted in death. Throughout, Strong Island is extremely emotional ... at times it's hard to watch, especially when Ford speaks in closeup.
The underlying theme ... it's more than subtext, but it's secondary to the emotional trauma ... is of race in America, and how it destroys lives, one at a time. Ford worked on the film for ten years, and when he started, names like Trayvon Martin were still in our future. Ford carefully constructs the history of his family so that we know that the story would be quite different if they were white. And in the ten years he was making Strong Island, it gradually seemed like every week there was another story of a dead African-American male taken down under racist circumstances. The story of Strong Island fits into those patterns, but Ford mostly leaves it to the audience to place things in a social context that reflects on our country's racism. Ford wants to show how his family was destroyed by the murder of his brother ... we can extend that to a general dissolution of society, but what grabs us as we are watching is the intense emotionalism of the Ford family story.
Ford doesn't present the material in a chronological fashion, and he cheats a bit by withholding some information until the movie has run for an hour. But by the time we get that information, Ford has given us equally important information about the Fords and their history, from the time the parents married, to the birth of their kids, to their move to Long Island, so that when tragedy strikes, it hurts especially hard because we know these people. 9/10.