This article was published in collaboration with the Marshall Project.

On November 3, 2000, a 22-year-old woman named Amy Kitchen went out for dinner at the El Rancho restaurant in Dallas, Texas, with her father, Jerry, and her fiancé, James Mosqueda.

I often try to imagine what that meal was like: Amy chatting with her dad about the classes she was taking in nursing school, the plans she had to go shopping with her mother the next day. Her dad giving her some money to spend; he always had a weakness for his only girl. James, 27, leaning back, sipping a beer. A waitress arriving.

It would have been an evening like any other—except for the fact that it was the couple's last.

Later that same night, the state of Texas says, James's cousin, Ivan Cantu—motivated by his relative's drug debt and his own greed and jealousy—killed Amy and James in an execution-style double murder. He is now on death row, and for 13 years I have been his loyal friend.

I never planned to be in this situation, to be friends with someone who could be executed. I live the mundane life of a working mother in Washington, DC—packing lunches, taking the bus to work, attending meetings, reading stories to my child at night, and, usually, falling asleep before ten.

But back in 2004, I had been inspired by progressive Catholics to reach out to someone on death row. So I answered a plea from the Community of Sant'Egidio, a worldwide Catholic prayer and charity organization, to write a letter of solidarity to a mentally-disabled death row prisoner named Johnny Paul Penry. It was part of a campaign to overturn his sentence for a 1979 rape and murder.

Johnny wrote back—and so did Ivan. They lived in adjacent "pods," as they are called on Texas' death row, the Polunsky Unit. Ivan would help Johnny write letters, but he was looking for his own friends on the outside, too.

It was mainly out of pity that I replied to Ivan. I never would have guessed where it's led me.

His letters and cards now fill a Rubbermaid container nestled into a bookshelf beside my bed. Just a stack of words on paper, they are also a chronicle of the past 13 years: descriptions to him of my travels as a development consultant; his accounts to me of trying to get innocence projects, journalists, and attorneys to listen to his case. The birth of my son. His struggle to live alone 23 hours a day.

Ivan is 44; I'm 42. He and I write once or twice a month, and there is not a letter I receive in which he doesn't encourage me in some way, and ask how my son and husband are. I count on his letters and, he says, he counts on mine. He also says there's a picture of my family, which I sent him years ago, taped to the wall of his cell.

Ivan pleaded not guilty and has consistently maintained he's innocent. I've always believed his story, but only because I had no reason not to. It didn't cost me anything, and I knew it would cost him everything if he really were innocent and no one listened. I never asked too much about the murders, never wanting to delve into that darkness.

That is, not until now. With Ivan's execution approaching—he lost his federal appeal in June, and if Texas has its way, he'll probably be executed within a year—there's nothing left to lose.

Last year, when the court published a denial of Ivan's previous appeal, I asked his wife, Tammy, to send me everything: the trial transcript, the crime scene photos, the legal documents, Ivan's side of the story and any documentation from the investigations.

I knew that immersing myself in the details of the crime would mean trying to understand both sides, asking tough questions, and entertaining possibilities about Ivan that I'd never allowed myself to. When I sat in my living room, watching my son's face as he laughed at the cartoons on TV, I would think to myself, My child knows nothing about the world's brutality, so why am I inviting this dark story into our house? Why am I complicating our lives in this way? But when the material arrived (a thumb drive along with printed documents), I started devouring all of it whenever I could—during my crowded bus rides home through downtown DC, and sitting up in bed, late into the night, after my son had gone to sleep.

I held a giant white binder and read from it, as if it were a movie script. I had to keep reminding myself that this happened—on a November evening in Dallas, all of this happened.

I am overwhelmed by all the evidence against Ivan. While there's no record of physical evidence proving that he was at the crime scene—no fingerprints, no shoe prints, no DNA—the crime scene was all over him. Jeans and socks with the victims' blood on them, found in Ivan's trashcan; James's Corvette found parked in front of Ivan's apartment the day after the murder.

But the person presented at trial doesn't match the one I know: a friendly and intelligent man who cuts out New Yorker cartoons and tapes them to his typewritten letters.

The philosopher and theologian Paul Tillich once wrote, "Doubt is not the opposite of faith. It is one element of faith." Perhaps cultivating doubt in Ivan's story is part of having faith in him.

Last August, I visited Ivan on death row and asked him if he committed this crime. His response was immediate: "Oh my goodness, no," he replied, solemnly. "But I know you have to ask that, I get it."

He spoke rapidly during our hours together, anxiety and desperation pervading his words and gestures. He talked openly about the crime, who could have done it and why, and what he believes still needs to be investigated. And because we are friends, we also talked about the mundane: music, books, NPR shows, anything to get his mind off the bleakness of solitary confinement.

I left the prison that day shaken. I don't believe in the death penalty, and even if he is guilty, I don't think he should die. I was overwhelmed by the responsibility of saving Ivan's life while knowing at the same time how little I could actually do.

And I was still unsure about the truth.