“The Staircase” stood out in 2005, that much is unambiguous. When it debuted, serious documentaries didn’t usually air on basic cable, and most had running times of around two hours. Unlike much cable-TV coverage of crime, then or now, it was deliberate and thorough. As a Frenchman, Mr. de Lestrade aimed partly to put the U.S. justice system under the microscope, as he had in his Oscar-winning 2001 documentary “Murder on a Sunday Morning,” which chronicled the case of a poor African-American teen accused of killing a tourist in Florida.

Mr. Peterson had far more money and resources than that defendant, but he had also been a newspaper columnist who had needled Durham politicians and prosecutors. It also emerged that he is bisexual, a fact prosecutors relentlessly used to imply that he could not be trusted, not just as a spouse but as a human being. Without going into details that would spoil key aspects of the show, other elements of the prosecution proved even more problematic. As one lawyer says late in the season, “It’s pretty devastating to see what can pass for science and justice in a courtroom.”

Despite Mr. de Lestrade’s compassionate approach, there are gruesome elements, and in lesser hands, “The Staircase” could have been a vehicle for crude voyeurism. Instead, the series is infused by a sense of intelligent curiosity and unforced immediacy. One expects to hear Mr. Peterson’s 911 call and to see late-night conferences among fatigued lawyers, but Mr. de Lestrade also follows family members as they visit Ms. Peterson’s grave, throw birthday parties or simply stare into space after the latest devastating setback.

There’s an element of luck at play — there’s no way Mr. de Lestrade could have seen some of the case’s most jaw-dropping twists coming — but he deftly folds even the most shocking developments into measured episodes that rarely wander or overstay their welcomes. And despite the grief at its heart, “The Staircase” never lapses into grimness or plodding pessimism. People laugh and make dark jokes, and Mr. de Lestrade allows quiet moments to breathe. His outdoor compositions are particularly evocative; a scene in which a woman detaches rose petals from a stem as she stands over a grave is both gorgeous and elegiac.