Twice I’ve described Kitty Green’s curious, alienating docu-whatzit Casting JonBenet to friends, and twice I’ve been asked, with surprising heat, “Why?” and “What’s the point?” So, this time, before we get into the specifics of what this documentary actually documents, let’s take a moment to consider what the film isn’t — and what truths Green, via her resolute unorthodoxies, manages to expose.

Far from a straight newsy doc recapitulating the facts of the 1996 murder of the child-pageant queen, or an investigative attempt to crack the case definitively, Casting JonBenet becomes a study of what we think we know and the casual ease with which we dish about real people who have been in the news. “She probably was the royal bitch of a mother,” one Boulder resident says of Patsy Ramsey, JonBenet’s mother, addressing the camera as if he were jawing at you over beers. Asked, apparently, if Patsy might have been the murderer, another local, a woman, concludes: “I hope she didn’t, but I think she might’ve.” One truth: Put on screen, Americans’ gossipy chatter sounds damnably cruel. We’re a nation of Nancy Graces.

From there the film becomes an exploration of how our certainty about strangers’ secrets and motivations often has roots in our own experiences of trauma. Then it becomes an examination of the ways that actors draw upon their own personal traumas, real or imagined, in order to inhabit the characters they play. That’s a grab-bag of ideas, but Green’s doc — like the case at its center — defies resolution or easy answers.

It’s her method that makes my friends balk. At a studio in Boulder, Green auditions 72 area actors for roles in a film drama about the murder; most of Casting JonBenet is made up of her conversations with these performers, many of whom claim some personal connection to the case. (This expands on the germ of the Australian filmmaker’s 2015 short, “The Face of Ukraine: Casting Oksana Baiul.”) Green encourages them to spill their thoughts about who killed Ramsey: Some suggest Patsy, bitter about turning 40 or angry that the 6-year-old sometimes wet the bed. Some suggest husband John or brother Burke or a neighbor who had dressed up as Santa Claus.

Despite the title, Green is casting JonBenet’s parents rather than the victim herself. She interviews only adults, though she still opens the film on a flock of ersatz JonBenets, present-day tykes in star-spangled leotards and makeup as thick as a Wendy’s hamburger patty, a disturbing re-creation of what was already a parody of feminine purity and perfection. (One potential Patsy says, of pageant contestants, “A lot of those girls go on to do great things — or work at Hooters.”) Late in the film, as a cruel jolt, Green occasionally has one of these wee girls let loose with a scream, but she otherwise avoids the most obvious provocations.

After treating us to much reckless speculation about the facts of JonBenet’s death, the actors take their turns running through scenes too difficult to possibly work. Each woman has a go at playing Patsy — whom some of them know — as she telephones the police to report that her daughter has been kidnapped. The wannabe Johns each get the opportunity to act out the discovery of JonBenet’s body in the family’s basement. Sometimes the filmmakers frame and score these scenes like excerpts from a typical docudrama.

Never an outrage, the film is fitfully interesting, occasionally fascinating, sometimes a provocative experiment and sometimes prankish and mean. Yes, it’s funny that the man who identifies himself as a “sex educator” announces, during his audition for the role of the investigating police officer, “Me, personally, I love breast torture.” But it’s also clear that — presuming he wasn’t fed that line, that he’s not acting a “sex-chatty actor” role — he’s been goaded by an interviewer behind the camera to keep the interruptions coming. Those interruptions then get cut to without lead-in or context, so it seems that he’s simply volunteering off-putting information unbidden, just as some of the actors’ most vicious remarks must have come in answer to questions we never hear. In these moments, Green succeeds only at that most dubious of goals: challenging the distinction between fact and fiction. Is it too much to ask for illumination rather than muddying?

It’s never clear how much the actors know about Green’s project — if they truly hope to land a part or if they understand that the auditions are the film. Eventually, though, the layers of reality and its opposite coalesce into something fresh. Green gets them to open up about their own encounters with death and abuse and takes pains to show us how those memories inform their acting. The arrangement of the scenes suggests that talking frankly about their own lives deepens their empathy for the family that, half an hour before, they were cheerily disparaging. Green saves the most potent of the performances for the end, when her actors (pro and amateur) connect and commit themselves to the Ramseys. They can’t play the full truth of those moments — only the killer knows what actually happened — but they each find a truth. Green closes with an exquisitely staged panorama of many of her actors on a set, all performing their roles at the same time. It’s a panoply of Ramseys, each unknowable.