For better or for worse, Errol Morris' 1988 documentary The Thin Blue Line has become so influential that it's now commonplace for documentary filmmakers to use (however cheesy) reenactments whenever they get the chance. Additionally, Morris' investigative piece, which argued that a man had been wrongly convicted of murder thanks to Dallas County's corrupt justice system, won awards from the New York Film Critics Circle, the National Society of Film Critics, and the National Board of Review. All that, and the overturning of the death-row conviction of its subject, too.
“If there was ever a film with a lock on an Academy Award,” wrote Jack Mathews in the Los Angeles Times, “Erroll [sic] Morris' The Thin Blue Line appeared to be it. It had a profound topic, overwhelming critical acclaim and the kind of respectful media coverage that benefits the entire industry. Morris himself was the subject of a 15,000-word profile in New Yorker magazine, and there were those in Hollywood who thought he might become the first person to receive a best director nomination for a documentary.”
The Academy's Documentary Committee, however, remained unimpressed. As per Mathews' piece, “all but one of the members interviewed said they did not consider it one of the five best films they saw. In fact, at the committee screening of The Thin Blue Line, enough members raised their hands to have the film stopped before it was completed.” Ultimately, The Thin Blue Line failed to receive an Oscar nomination for Best Documentary Feature.
“I think (the distributors) set the film up as a shoo-in and that it created an expectation among members that the film couldn't meet,” committee member Mitchell Block told Mathews. “But there was no backlash. As a group, we simply thought the five nominated films were better.”
Roger Ebert disagreed, calling the Thin Blue Line omission “the worst non-nomination” of the year.
For the record: the five nominated documentary features in 1988 were Robert Bilheimer's The Cry of Reason: Beyers Naude - An Afrikaner Speaks Out, Bruce Weber's Let's Get Lost, Ginny Durrin's Promises to Keep, Christine Choy and Renee Tajima-Pena's Who Killed Vincent Chin?, and the eventual winner, Marcel Ophüls' Hotel Terminus: The Life and Times of Klaus Barbie.