This week marks two years since Diane Schuler, a 36-year-old Long Island “supermom,” caused a collision while driving a minivan the wrong way on New York’s Taconic State Parkway. She killed herself and seven others, including her 2-year-old daughter; her three nieces (ages 5, 7 and 8); and three men in the sport-utility vehicle that she hit head-on. It’s one of those ghastly crashes people will talk about forever.

Especially because of Schuler’s autopsy results: Sometime after packing up and leaving her family’s annual Catskills camp-out on a Sunday morning for the 140-mile trip home, Schuler began bizarrely zigzagging off her usual route. For reasons unknown, she consumed enough vodka after leaving the camp (a 1.75-liter bottle of Absolut was found in the wreckage) to attain a blotto-level blood-alcohol test result of 0.19, according to investigators — more than twice the legal limit for motorists. Lab results revealed Schuler also smoked marijuana that day.

There’s something wrong with Aunt Diane — that’s one of the last things Schuler’s 8-year-old niece, Emma Hance, worriedly told her father by cellphone as the minivan sped hither and then yon, minutes before Schuler got on the Taconic going the wrong way. By then, they’d been on the road for more than four hours.

“There’s Something Wrong With Aunt Diane” is also the title of Liz Garbus’s grievously mesmerizing HBO documentary airing Monday night. Ostensibly an objective inquiry into the tragedy, the film is perhaps better interpreted as a study in the infinite and even seemingly inappropriate ways that people experience profound grief.

If you come here looking for answers to this much-discussed event (which briefly preoccupied Larry King and other members of the cable and Internet commentariat), you will leave deeply unsatisfied and possibly smoldering with disgust. If you can stomach the material, then watch. If you can’t — and I include a special caution to those who’ve lost loved ones to a drunk driver or any vehicular crash — then it’s time to change the channel.

Still, it’s hard to look away from what Garbus has attempted here. “There’s Something Wrong With Aunt Diane” is the most unforgettable and hauntingly rendered documentary to come from HBO so far this year; at the same time, it is an example of the documentary format at its most fraught and incomplete.

Seeking truths

Garbus, whose credits include “Bobby Fischer Against the World” (which aired in June on HBO), gained tentative access to the Schuler family to make this film.

We watch as Schuler’s husband, Daniel, and his brother’s wife, Jay, agree to talk about the incident and its aftermath, but only because they remain convinced that the coroner’s findings were somehow wrong. They hope Garbus and her crew will turn up new evidence to refute the irrefutable — that Diane was profoundly drunk — and to somehow partially restore the reputation of the woman they thought they knew.

Garbus cautions the family that the film may have the opposite result. Part of what saves “There’s Something Wrong With Aunt Diane” from total despair is its structure as a work in progress and its willingness to bring the viewer along on the search. Diane’s brother and his wife — who lost all three of their children in the crash — declined to participate in the film and have severed contact with the Schuler family, but Garbus was able to interview the relatives of the men in the SUV.

As those familiar with the case know, Daniel Schuler and some of his family members have a troublesome grasp on tone. During their many media appearances after the crash, their shock and mourning took the form of denial: Diane never drank heavily, they said. Diane never smoked pot. Diane would never. Not our Diane. Our Diane held down a six-figure job. Our Diane was the perfect wife and mother. They hired a TV-savvy lawyer who, in turn, hired another showboat, a high-priced investigator, to double-check the toxicology evidence.

But it is Garbus and her crew who present the Schulers with more medical records and paperwork than they’ve ever seen from the investigator. (In a phone call taped by Garbus, the investigator demands payment in exchange for an interview. Garbus declines.)

The Schulers are particularly intrigued by Diane’s dental records, which they hope will show an abscessed tooth or other problem so painful that it sent Diane into delirium, which caused her to mistake the bottle of Absolut for water. Or caused an infection that then caused her to have a mini-stroke. To Daniel and Jay, these theories are somehow more plausible (more palatable, frankly) than the idea that they were living with a closet alcoholic who would endanger children.

To the families of the other victims, these test theories are all, of course, an abhorrent exercise in denial.

Inconclusive void

Cracks begin to show in the Schulers’ story. Interviews with childhood friends reveal that Diane cut off contact more than a decade ago. An interview with another friend becomes curiously clenched on the subject of Diane’s upbringing and the state of her marriage. Garbus seeks the aid of a forensic psychologist, who tries in vain to work back through some of the issues that might have driven Diane to drink that day.

A year goes by. Once the investigator reluctantly provides results of the new toxicology test — confirming that Diane was drunk and stoned — the dutiful sister-in-law, Jay, veers off into a private tirade about how she provides most of the care for Diane and Daniel’s 7-year-old son (who survived the crash), while Daniel obsesses on restoring his wife’s reputation. Whether by the demands of film editing or bizarre dissociation, hardly anyone in the film mentions the death of the Schulers’ 2-year-old. It’s all Diane, all the time. The access the family granted Garbus begins to dry up, as everyone begins to realize that Diane’s story will always end at an inconclusive void.

At this point, Garbus is necessarily spackling over the big holes in the story with eerie, resonant interludes of security camera footage of the minivan pulling up to a Sunoco gas pump. On camera, Diane walks in and out of the convenience store. Then we watch again. And again. Nothing reveals itself.

I must warn you (as does a disclaimer at the beginning of the film) that we are eventually shown photos of Diane’s body sprawled on the median grass, her eyes half-open, her face a blank death mask. Thankfully, we aren’t shown the bodies of the children or the other victims.

“There’s Something Wrong With Aunt Diane” will probably send many of its viewers to the Web for additional facts, half-truths, rumors and outrage. They’ll find plenty there, some of which should have been included in the film and wasn’t.

Among these rumors are reports that Daniel Schuler was paid $100,000 to participate in the film. When I asked HBO’s documentary publicist about this, she told me that all of the families in the film were paid a “small honorarium” for their time and the use of family photos. (“Nowhere near $100,000,” the publicist added.) From a journalist’s perspective, I’m depressed to learn there was any monetary exchange at all.

I’m also perplexed by the rush to finish and air the film. More-patient viewers will be left wondering what sort of documentary might have emerged if Garbus had stuck with it a few more years, following the family off and on as its grief evolved (or devolved).

Clearly, “There’s Something Wrong With Aunt Diane” wasn’t meant to come off like a lurid “Dateline NBC” episode. It was potentially about something much darker, much deeper. It could have been — and in many ways is — a contemplative piece on sorrow.

There’s Something Wrong With Aunt Diane

(100 minutes) airs Monday
at 9 p.m. on HBO.