In the late 1970s, Elmo Patrick Sonnier was sentenced to death for a rape and double murder in St. Martin Parish. He was executed at Louisiana State Penitentiary at Angola on April 5, 1984, but not before his case became a cause célèbre for opponents of the death penalty.

In the forefront of the opponents was Sister Helen Prejean.

During Sonnier’s final years, while his appeals were going through the court system, the Louisiana-born nun served as his personal spiritual adviser. Her experience led her to write the bestselling book, “Dead Man Walking,” which went on to become an Academy Award-winning film, a stage play and an opera.

This weekend, the opera version of “Dead Man Walking,” composed by Jake Heggie in 2000 from a libretto by Terrence McNally, will have its first staging in the state where the action took place. Presented by the New Orleans Opera Association, it opens at 8 p.m. Friday and repeats at 2:30 p.m. for a Sunday matinee.

Mezzo-soprano Jennifer Rivera sings the role of Sister Helen in the production and baritone Michael Mayes is Joseph De Rocher, the pseudonym given to Sonnier by the librettist. This will be the third time Rivera and Mayes have performed their roles together.

Prejean, 76, is expected to be in the audience during the Friday evening performance.

Rivera, who has spoken to Prejean on the phone but has never met her, is looking forward to both the upcoming performance and the meeting. But, initially, Rivera had some trepidation about taking on a role she termed “emotionally wrenching.”

As Rivera explained, “It was very hard for me to approach the opera for the first time from the point of view of the character, because I have a child of my own. I related immediately to the characters of the parents in the opera, and I understood their horror at Sister Helen being a counselor to the person who killed their children.”

However, as she delved further into the role and had more discussions with Prejean, Rivera developed an admiration and respect for the activist nun.

“It’s very hard not to admire someone who is willing to see the humanity in every person and who goes through an extremely difficult journey, emotionally, every time she involves herself in one of these situations.

“She’s a real person, and I want to do her justice,” Rivera added. “My biggest desire in performing this role is to effectively portray this remarkable person who does so much for the most ignored people in society.”

Rivera noted that performing opposite Mayes on previous occasions has enabled them to develop an onstage chemistry. “It definitely makes a big difference. There’s a lot of realism in this show. The more you perform it with your co-star, the more it increases the intensity of the performance,” Rivera said.

Concurring with Rivera’s assessment, Mayes said, “Jenny and I actually have this sort of symbiosis now; this really organic way of communicating because we both know each other’s roles so well. It’s been really great to work with her this much.”

Mayes, who also has sung several other roles in Heggie’s canon of a half-dozen full-length operas, describes the 45-year-old composer as “an incredible mentor and adviser to me. He’s so giving of himself and open to suggestions.”

Mayes added: “I’ve always been a fan of opera with a conscience. Opera that is meant to reach out and grab people and shake them, and have them confront large issues. This is one of those. It isn’t a question of whether or not Joseph is guilty. He absolutely is. The way his character is written, the audience can focus much more on his journey to redemption.”

Other supporting roles in the opera and those performing them are Adrienne Danrich as Sister Rose, Margaret Lattimore as Mrs. De Rocher, Tyler Smith as Howard Boucher, Kathleen Halm as Jade Boucher, Dennis Jesse as Owen Hart, Amy Pfrimmer as Kitty Hart and Casey Candebat as prison chaplain Father Grenville.

“Dead Man Walking” will be sung in English with the dialogue projected above the stage. Robert Lyall conducts the Louisiana Philharmonic Orchestra and Tomer Zvulun directs.