Every now and then, a contemporary opera comes along that is so powerful, so gripping that it pulls you into the action onstage — and one so artfully written that it invites comparisons with classic operas in the standard repertoire.

Such is the case with “Dead Man Walking,” composed by Jake Heggie in 2000 from a libretto by Terrence McNally.

Based on the true story of Sister Helen Prejean’s experiences spiritually counseling a convicted murderer in Louisiana during the months leading up to his execution, “Dead Man Walking” will be given its final New Orleans Opera Association staging at 2:30 p.m. Sunday in the Mahalia Jackson Theater for the Performing Arts.

Prejean, an outspoken opponent of the death penalty, served as the spiritual adviser to Elmo Patrick “Pat” Sonnier, who was convicted of the murders of a young couple in St. Martin Parish in 1977 and sentenced to death. Sonnier was executed by lethal injection six years later but not before receiving widespread publicity from those opposed to capital punishment.

In the opera, Sonnier’s name is changed to Joseph DeRocher; the names of the victims, their parents and other principals are changed as well.

Sister Helen, whose name is unchanged, faces the daunting challenge of persuading a defiant killer on death row at the Louisiana State Penitentiary at Angola to confess to his crime so he can receive forgiveness and possible redemption.

While this tug-of-war is going on, it becomes painfully apparent that the murdered teenagers were not the only victims. When their parents and Joseph’s mother come into the action, the audience is given the all-too-real perspective of those who have to go on living with their agonizing losses.

As Sister Helen, mezzo-soprano Jennifer Rivera sings with a smooth, polished delivery and is also a skilled actress. With the nun caught between her duty to her religious vows, her mission to the confused young man in her charge and her empathy for the plight of the parents, Rivera makes the stress the character is undergoing clear for all to see.

She delivers her best aria, “Who shall walk with me?” after an emotionally wrenching scene in which Joseph sees his mother and two younger brothers for the last time. “Bravas!” are in order for that one.

Michael Mayes, as DeRocher, is also convincing in his role, using his sonorous baritone to portray moods ranging from swaggering defiance to his character’s final emotional breakdown and pleas for forgiveness that almost — but not quite — make you sympathize with him.

Soprano Adrienne Danrich, as Sister Rose, sings with great clarity as a comforting companion to the emotionally torn Sister Helen, combining with her for a sweet duet after Sister Helen agonizes through a sleepless night.

But star billing, if any is to be cited, would have to go to mezzo Margaret Lattimore, who, in her limited role as DeRocher’s mother, has the two arias that best fit the conventional definition of the word. “Gut-wrenching” is the description that comes most readily to mind.

In the first aria (“Haven’t we all suffered enough?”), she appeals to the pardon board to spare her son’s life, citing his rough childhood in a broken home. In the second, knowing she’ll never see her son again, she tearfully recounts memories of happy moments with her “Joey” before he went bad. Lattimore delivers a powerful presentation if ever there was one.

Meanwhile, four other parents must contend with losses of children.

Acting as a spokesman for the parental victims on several occasions is bass-baritone Dennis Jesse. As Owen Hart, father of the murdered girl, he makes clear there can be no forgiveness for DeRocher or for Sister Helen for appearing to side with him, although he does begin to relent a bit toward the end. His impassioned delivery is very convincing, as is that of the other parents, well sung by Amy Pfrimmer, Kathleen Halm and Tyler Smith.

Also notable are Casey Candebat as an occasionally funny but cynical chaplain and Ken Weber as a somber warden.

Robert Lyall conducted the Louisiana Philharmonic Orchestra masterfully through a score that probably none of the musicians had ever performed before. The subject matter being what it is, much of the music is dark and foreboding, but there are a few lighthearted moments as well.

The set design by Keith Brumley was convincing, especially the interiors of the prison.

At three hours (not including intermission), “Dead Man Walking” is probably a bit too long for most tastes. Some scenes could have been cut down without sacrificing the full impact of the message, which, at times, comes across as overly maudlin.

Although the opera is sung in English, the supertitles projected above the stage were a big help to the audience. Large portions of the text might have been difficult to understand without them.