Tijuana.- Mother Antonia Brenner walks along the La Mesa state prison like a light in the midst of a long, dark tunnel. Her face glows, sweet and pained at the same time. She looks tired but smiles when she approaches the cells.

The prisoners – some of them accused of murder, rape or drug trafficking – hug her, pray and ask forgiveness for their acts. She relays to some of them words of comfort a relative has sent.

"You have not done something so bad that God cannot forgive you," the 83-year-old nun tells them time and again.

That's how the life of one of the most intriguing characters in the region is portrayed in the documentary, "La Mamá: An American Nun´s Life in a Mexican Prison", produced by San Diego journalist Jody Hammond and narrated by Susan Sarandon. It's being presented Saturday as part of the San Diego Latino Film Festival.

The 30-minute film shows the nun that spent 33 years of her life practicing her faith inside the penitentiary in Tijuana, even living in one of the 10-feet by 10-feet concrete cells.

And it also explores her contributions beyond the prison walls, such as opening shelters, launching civil organizations, and forming the religious community Servants of the 11th Hour. The name reflects a commitment to devoting the last part of one's life to serving God.

That is just what "Madre Antonia" did.

At age 50, Brenner's life seemed cast. She was a businesswoman in Beverly Hills, twice married and twice divorced, the mother of seven children. She abandoned all of that to become a nun and devote her life to working at Tijuana's prison.

"Her story amazed me," Hammond said. "She was never afraid to go to the penitentiary and help the prisoners, prove to them that she was with them, that she was willing to dedicate her life to them."

Hammond met Madre Antonia in 1990, when she was a reporter for Channel 8 and covered stories on the border. She spent five years with her to make the 30-minute documentary.

"My goal was to produce a short, powerful program that would not be boring," she said.

Among the documentaries she has produced are "Hands Up," about Vietnamese manicurists in California, and "Miracles in Tula," about San Diego doctors who travel to Mexican communities to donate their services.

The documentary "La Mamá" is narrated by Sarandon, who won an Oscar for her role as a nun in "Dead Man Walking" (1995). It begins with images of the fiery riots at the prison in September of 2008 in which at least 24 inmates died.

The images of the flames, the prisoners' protests, the chaos on the street, what Madre Antonia herself called "a war zone," underscore the courageous work she carried out inside the prison for more than three decades.

Various people in the documentary—including prisoners, officials, priests, politicians and even her own children – talk about Madre Antonia's work.

Another person shown is a smiling Mary Clarke, an American woman of Irish descent, surrounded by her children, who was still deciding whether to become a nun.

Madre Antonia left the prison last year to recover with her family from a bronchial infection. Other members of the Servants of the Eleventh Hour continue her work there.

Even though its subject is the life of a religious woman, the documentary does not preach. It's an accurate, austere look at a woman committed to easing the pain of society's caged outcasts.

Omar.millan@sandiegored.com