Mr. Ridley, who directed three episodes of the show and wrote five, returns to TV, where he started in the early 1990s as a writer on “Martin” and “The Fresh Prince of Bel-Air,” after a few years doing big screen work — as a co-writer of the screenplay for the Tuskegee Airmen movie “Red Tails,” directing Outkast’s André Benjamin as Jimi Hendrix in last year’s “Jimi: All Is by My Side,” and of course, winning the Academy Award for “12 Years a Slave.”

It was that film’s success at last year’s Oscars that, for many, brought this year’s nominations into relief. “I was just rewarded a year ago, so it comes off maybe a little disingenuous for me to be the one who rallies about change,” said Mr. Ridley, when asked about diversity (a word he dislikes for its “throwback” connotations) and the Academy. “At the same time, I think we in Hollywood can do a better job, I think we should do a better job, but I don’t think we should look at one year and decide how we’re doing on progress.”

Race, and the friction it can lead to, is one of the main themes of “American Crime.” And it’s in the character of Barb Hanlon, Russ’s former wife, that we see that discomfort come to a head in a way that feels downright shocking and even repugnant. As Barb, Ms. Huffman portrays perhaps the series’ most unlikable character: a mother seeking justice for her son. Her motives are understandable, but are undercut by her sometimes casual, sometimes direct bigotry.

Mr. Ridley was adamant about not creating what he called “straw people,” particularly in Barb’s case, “because I had an opportunity to write a white woman who may have viewpoints that are exceptionally different from mine, but they’re coming from a place that she believes is real,” he said.

He excelled, Ms. Huffman said, at shaping a nuanced survivor whose parched inner life and adversarial relationship to the world have given rise to prejudices that she explains away as pragmatism.

“We’re past the broad, sweeping generalizations of ‘those people are inferior, those people are this, those people are that,’ ” Ms. Huffman said. “Which is why people think, ‘Oh, aren’t we done with racism?’ And you go, ‘No, no, there’s a whole new face of racism.’ And I think that’s possibly Barb.”

Mr. Ridley knows he has created an ugly person on his show. And he hopes she does her job. “There may be people who believe what Barb believes,” he said. “And to a degree I want them to go, ‘O.K., good, you go, girl.’ But then they’re going to have to take that same journey that Barb is taking. And if they do, are they ready to come along for the ride and see all of the ramifications?”