William J. “Dub” Lawrence, a former Utah sheriff, guides viewers through “Peace Officer,” a documentary that focuses on the militarization of law enforcement throughout the United States. (Submarine Deluxe/Gravitas Ventures)

The title of the documentary “Peace Officer” is both literal and ironic. From one perspective, it refers to William J. “Dub” Lawrence, the former Utah sheriff who serves as the film’s heart and soul. Lawrence, who runs a water and sewage pump repair service, established his county’s first SWAT team in the 1970s, only to watch, helplessly, as members of that force killed his son-in-law many years later during a 2008 standoff precipitated by a domestic dispute. In addition to his day job, Lawrence works as private investigator, doggedly examining cases of police overreaction and often uncovering evidence of cover-up and sloppy policing in the process.

Although “Peace Officer” is not a personal profile, Lawrence acts as a genial and knowledgable guide to the film’s true subject, and the source of its titular irony: the increasing militarization of law enforcement. Contemporary cops, as directors Scott Christopherson and Brad Barber cogently argue, all too often treat conflicts with the community they are supposed to protect as potential battle zones.

Lawrence provides many of the film’s specific details that bolster this argument, as Christopherson and Barber accompany him to crime scenes, which Lawrence has meticulously reconstructed after what are typically chaotic, violent and confusing raids. The evidence that we’re presented with on camera often contradicts the official police report, in troubling ways. Interviews with such experts as Radley Balko, the author of “Rise of the Warrior Cop: The Militarization of America’s Police Forces” and a blogger on criminal justice for The Washington Post, present the bigger picture. It’s one of a police culture that increasingly resembles the armed forces, with armored vehicles and weaponry — and a shoot-first-ask-questions-later mentality — that are alarming.

In making this case, the documentary’s greatest strength lies in Lawrence. A retired police officer with a history of support for SWAT actions in principle and in practice, he is well cast, if that’s the right word. Lawrence never gets worked up as he presents his forensics, despite his obvious personal stake in the problems he’s describing.

His tone is always that of a calm but concerned citizen.

The same cannot be said for the viewer’s potential reaction. “Peace Officer” piles up evidence of outrageous excess, provoking what is likely to be a response, from its audience, that is far less measured than that of its main subject.

Unrated. At Landmark’s E Street Cinema. Contains images of the aftermath of violence.
109 minutes.