Barbara Kopple is one of the legends of documentary filmmaking. “Harlan County, USA,” a riveting cinema verite account of a bitterly fought miner’s strike in Kentucky, collected an Oscar in 1976. “Shut Up and Sing” was a stinging remembrance of the price country music’s Dixie Chicks paid for speaking out against a war and an incompetent president.

When ESPN wanted to tackle the history, money and power of Yankees ownership during its glory days, Kopple came in to film the “30 for 30” “House of Steinbrenner.”

So there are expectations built into any film she puts her name on. As “A Murder in Mansfield” begins, the mind races about where she might go with this recounting of a 27 year old murder case.

An Ohio doctor is accused of bludgeoning his wife to death, burying her under the concrete floor in his basement, so that he could marry his pregnant mistress and not pay alimony in doing it. And the star witness for the prosecution, the person who seals his fate is his 12 year-old son.

In courtroom footage, young Collier Boyle is composed. He answers questions in the polished language of an adult. He uses terminology that seems straight from TV courtroom dramas, and when he stumbles off-script, he giggles and corrects himself.

When the big questions lead to the dramatic accusation, what he heard, what he was sure had happened, he turns, with theatrical flair, to the jury — Or is it the camera? — to finger the man who bludgeoned and buried his beloved mother.

This footage is so dramatic, so loaded that you can see why Kopple would use it. Is she setting us up for an expose of the justice system, how very young witnesses can be coached to win (perhaps unjust) convictions?

No. The doctor, a murderer without remorse, did it. When you’ve bought a jackhammer a couple of days before committing the crime, that’s about as clear a case of premeditation as we could ever hope to see.

What Kopple and aspiring filmmaker Collier (who now goes by Collier Landry) are interested in exploring here is the ripple effect of a single act of violence, the lives overturned, the chasm left in lives by the sudden loss of a mother, a friend, a pillar of a community.

Collier wanted, back then on the witness stand, to “do right by my mother,” who indulged him, took him with her everywhere and was raising him in her image — a mamma’s boy who appreciates the finer things (Louis Vuitton handbags, etc). Now he’s looking for closure, to meet the adoptive sister that the state separated from him when their father was convicted, to renew acquaintances with families that took him in, the detective who investigated the case, others who knew his mother.

He wants to wring a confession and sense of remorse from his estranged (adoptive) father, a man who tellingly nicknamed him “Stupid Little Fat Boy” in his childhood. Collier wants revenge.

And if none of that sounds terribly compelling, feel free to check out of this review right now. Because, in all honesty, it isn’t.

Collier talks the new owners of his parents’ house into letting him tour it, and dramatically points out where the crime was committed, how near he was to dying the same night (or perhaps later, as his father wanted to take him on a “vacation” to Mexico). He hears from the people who took him in, who remind him of the curious questions he asked after moving in — their income, how many Louis Vuitton bags the foster mother owned.

He never meets and renews his relationship with the much-younger sister whom he claims actually witnessed the murder.

Basically, this is a film that directs us to a final confrontation with the still-imprisoned father (whom Collier vouched for in parole hearings), trying to wrangle a blunt admission of his guilt.

Landry doesn’t make the most riveting tour guide through all this, even in the most emotional moments. He comes off as affected and effeminate in the archival footage at age 12, and that’s just as glaringly obvious (and unaddressed in the movie) now.

The best footage is that courtroom coverage in the film’s opening, and an absolutely chilling police video of the basement search, the digging and the discovery and removal of his mother’s body, something Landry sees for the first time, on camera.

It’s just awful, and you can see the film’s thesis — a crime of violence rippling through lives and through time — in just that scene. Who could know somebody murdered like that, and the details of it, and not be scarred for life?

It’s a shame that the rest of “A Murder in Mansfield” is so utterly routine, strictly cable TV “true crime” filler. Kopple has done better, and in the decades since she became a documentary film icon, many others tackling similar subjects have as well. “Mansfield” feels incomplete, reality TV that doesn’t quite the deliver the drama.

MPAA Rating: unrated, graphic crime scene photos, murder discussed explicitly.

Cast: Collier Landry, Dr. John Boyle

Credits:Directed by Barbara Kopple. A Cabin Creek release.

Running time: 1:29