Matthew Poncelet (Penn) has been waiting to die for six years. He has spent this time on death row at the Louisiana State Penitentiary, having been convicted of killing a teenage couple with one Carl Vitello. During his incarceration, Poncelet has been corresponding with Sister Helen Prejean (Sarandon), and now that his day of execution by lethal injection looms closer he asks her to help him with a final appeal.
While Poncelet is arrogant and off-putting during her first visit, he maintains his innocence, and Sister Helen forms a special relationship with him as she fights to have his sentence commuted, determined to save his soul even if she can't save his life.
This film contains the following tropes:
- As the Good Book Says...: At one point the warden and Sister Helen get in a debate about whether or not the Bible condones the death penalty for murderers. The warden folds early by stating "I'm not gonna get in a Bible-quoting contest with a nun, because I know I'm gonna lose."
- Based on a True Story: The actions of Elmo Patrick Sonnier and Robert Lee Willie, two death row inmates Prejean counseled.
- Beauty Inversion: While still reasonably attractive, Sister Helen Prejean is considerably de-glammed from Susan Sarandon's usual look, as befitting a nun.
- Believing Their Own Lies: Poncelet maintains his innocence from the beginning, holding firm for most of the film. Towards the end, though, he breaks down and admits his guilt. It is likely that he purposely suppressed the memories of his part in the crime.
- Bittersweet Ending: Matthew dies, but not without expressing sincere remorse for his crime. And the fact that the father of the boy who was killed is seen praying with Sister Helen at the end indicates that he is taking the first steps to healing.
- Both Sides Have a Point: The film presents a fairly even handed look at capital punishment.
- Dead Man Walking: The Trope Namer, being about a death row inmate.
- Death Row: The setting of much of the film.
- Dies Wide Open: Poncelet's eyes close during his execution when the anesthetic takes effect, only to open again when he dies.
- Even Bad Men Love Their Mamas: Matthew genuinely gets along with his family when they come to visit him before his execution and among his last words to Helen are asking her to check in on his mother occasionally.
- Foregone Conclusion: It's clear from the start that Matt is going to die, regardless of what Helen does. Much of the plot revolves around getting him to express remorse before he does.
- He's Dead, Jim: At the moment of his death, Poncelet's eyes drop open, and the EKG he is attached to flatlines.
- Hollywood Nuns: Subverted here, as this movie is based on a true story, but the wearing of the full habit is discussed when Sister Helen points out the Pope's ruling that it wasn't necessary anymore.
- Last of His Kind: Earl Delacroix tells Helen that, due to Matt's actions, he is the last Delacroix and the family name will die with him. Helen is clearly taken aback by this.
- Match Cut: We go from an overhead shot of the teens bodies laid out in the woods to one of Matthew lying on the stretcher in virtually the same position.
- Maybe Magic, Maybe Mundane: After a gritty, realistic movie, we get an image of the two murdered teenagers watching Matthew's execution.
- Nice Girl: Helen is kind, compassionate, caring and sincerely believes that Matt isn't beyond redemption.
- One-Woman Wail: Heard during the execution sequence.
- Outliving One's Offspring: Happens to both the Percy's and Delacroix's and played for truly heartbreaking effect. Later it happens to Matthew's mother.
- Politically Incorrect Villain: Matthew makes a handful of racist and sexist comments, plus an interview in which he defends Hitler. Later he expresses regret to Helen for saying these things.
- Posthumous Character: The murdered teenagers appear in pictures and an extended flashback of their brutal rape/murder.
- Rape Is a Special Kind of Evil: Matt raped Hope before killing her.
- Spoiled Sweet: Helen grew up in a wealthy house with loving parents and became a nun because she felt obligated to give back for all her good fortune.
- Tattooed Crook: Matthew has a variety of tattoos on his arms.
- Title Drop: A guard calls out "dead man walking" as Matthew is escorted to the death chamber.