Welcome to “Aging at 24 Frames per Second,” a blog where I — Patrice Bowman — will review older films. Not just the well-known older films of the likes of “Citizen Kane” and “Psycho,” but others that have been obscured but fully deserve a closer look. In 250-500 words, I hope to distill what made a certain older film great — or not so great — and pass it along to you.

Not too many films can claim that they helped free a man from prison, but “The Thin Blue Line,” a documentary by Errol Morris, can. It’s also a frustrating paradox. The film is unsettlingly observant at first, but its oh-so-polite voice rises to a nag as it leads you towards what Morris wants you to believe.

Dallas, Texas, 1976. A highway at night. Officer Robert Wood pulled over a car. Shots rang out. Officer Wood fell dead. Did drifter Richard Adams deserve to be convicted of Officer Wood’s murder? Or did David Harris — a soft-spoken teenager with a taste for violence — pin the crime on Adams after a chance encounter? Swimming through faulty memory and down-right lies, Morris tries to prove Adam’s innocence.

Errol Morris’s first feature — “Gates of Heaven” (1978), about a pet cemetery in California — captured the quirky side of America, but “The Thin Blue Line” keeps up a formal façade. The film is like a stuffed dossier: interviews (startlingly, the subjects look right at you) are spliced in with newspaper articles, diagrams of the crime scene, and re-enactments. These re-enactments — rarely used in documentaries before — are crisp plays of light, darkness, and color crafted by cinematographers Robert Chappell and Stefan Czapsky. Philip Glass’s melancholic score, full of repetitive melodies, encircles you while keeping you at an arm’s length. But the narrative, even with its stylized approach, is a festering wound of falsehoods steeped in reality. And there’s no Hollywood-ending to clean it.

Errol Morris once said that “the truth is knowable, but often we have a vested interest in not knowing,” and he definitely wants you to know his truth. According to an interviewee in the film, the police are the “thin blue line” between anarchy and society. But those law enforcers are willing to ignore evidence against Harris and pin the crime on Adams because Harris isn’t old enough to be executed. In the opening credits, the “Blue” of the film’s title is invaded by disorderly red. The implications of such color usage and the police are obvious, but it all still makes your stomach somersault.

The editing, done by Paul Barnes, is also blunt in its portrayal of Harris and Adams. While Harris is accompanied with close-ups of newspaper articles detailing his unrelated crimes, the nearly-bloodless Adams rebuts the accusations of each clip of interviewees. While some scenes do question Adam’s innocence, they are unfairly forgotten in order to focus on Harris’s guilt and the incompetence of the police.

Documentaries, no matter how objective they claim to be, have a slant. I’m not faulting Morris for using this well-articulated documentary to prove Adam’s innocence; instead, I’m attacking this film’s lack of transparency. Documentaries have opinions because the people who make them have opinions. Such opinions need to be loudly announced, or else you’ll be tricked into thinking that you’re wading eyeball-deep in a moral uncertainty that never existed.