Brazil is a bounty for documentarians and filmmakers who work in a documentary style, from “Pixote” to “Bus 174,” “City of God” to “Favela Rising.” It seems as though every five minutes there’s a new saga, drawn from the nation’s ragged and sprawling social underbelly, that illustrates the squalor and desperation of its poor, usually offset by the earthy vibrancy of the hillside favelas and scenes of the non-stop party on the nearly nude beaches.

The documentary “Justice,” which begins a one-week engagement tonight at Film Forum, is not quite one of those. The film has a subdued, almost serene quality as it tracks the cases of three young men through the obscenely overcrowded jails and the grindingly slow courts in Rio de Janeiro. Maria Ramos, a Brazilian-born filmmaker who resides in the Netherlands, obviously believes that less is more, and restricts much movement of the camera. Instead, she parks it, usually to the backs or sides of her subjects, and simply observes. She eschews narration or talking-head interviews.

Like a Frederic Wiseman, Ms. Ramos maps an institution from every angle, letting the gravity of each situation sit as heavily on the audience’s shoulders as it does on the individuals she patiently films. It goes against the shock-cut, shaky-cam, ADD-friendly style common to the documentary form after two decades of MTV, but Ms. Ramos clearly understands that duration is essential to making her point.

It’s not very exciting.Yet, in its methodical, jitter-free approach, “Justice” is devastating. One particularly moving case involves Carlos Eduardo, a 23-year-old man arrested for car theft after enjoying a night on the town with three women he picked up at a disco. His 17-year-old girlfriend is about to give birth to a second child. His long-suffering mother, who labors as a domestic, is seemingly shredded by grief. Since it is Mr. Eduardo’s second such offense, his odds look bad. There is a tireless public defender, exasperated by her workload and what seems like the futility of a system that functions like a clogged pipeline. There is also a compassionate judge, whose promotion to a higher court near the end of the film leaves Mr. Eduardo to the mercy of a new judge who is unfamiliar with his case.

Following judges, the public defender, family members and the accused back to their homes, jobs, and jail cells between extended procedural sequences, Ms. Ramos excels in capturing the human side of the process, detailing how petty and usually pointless crimes seem to choke the system at its root.

The culprit has been stupid, indulgent, and careless, but by middle-class American standards, the six months he has already served in a Rio hellhole awaiting his verdict might seem punishment enough, especially with a new family to support. But, like all the defendants shown, he is impoverished and his options appear limited in every way.(Except, of course, the facility with which he can round up a car, drugs, and women on a moment’s notice, a bruising irony with which the sheepish Mr. Eduardo is immediately confronted at his first hearing.)

Ms. Ramos doesn’t try to draw conclusions. She simply shows how the suffering is spread all around, capturing moments of piercing intimacy in the most public places and measuring the distance between the letter of the law and the frustrations of those who must navigate its language to humane purpose. Even when someone is disgorged from the belly of this bureaucratic beast, the outlook is never too promising.

One 18-year-old boy, who appears four years younger, is released after a drug charge and returns to the street, hobbling on swollen ankles to a deserted underpass where he hails a bus and rides off into the night. The camera holds onto the fading taillights for a moment, and that’s it. Such matter-of-fact instances give “Justice” a harsh realism that is difficult to shake.