Just after midnight on Wednesday September 24, 1997, I watched as the state of Missouri put Samuel McDonald to death by lethal injection. I had never wanted to witness an execution, and I was devastated by what I saw. How did I come to be at the Potosi Correctional Institute on that night? It had to do with friendship, and with the unforeseen and frightening implications of taking even the smallest step forward in faith.

Since my late teens I have opposed the death penalty. I have had many reasons: Poor and minority defendants are executed in grossly disproportionate numbers. Innocent people are sometimes sentenced to death. There is no evidence that the death penalty reduces the rate of violent crime. The rest of the Western world has managed to function without executing criminals.

But the heart of my opposition grew out of my religious commitments. As a Christian, it seems to me that the death penalty violates the essence of Christ's teachings to choose mercy over revenge, to love our enemies and to forswear all violence.

For all of this, my opposition to capital punishment remained abstract. This was because, in the late 1960s,  capital punishment almost disappeared from the American landscape. It seemed gone for good in 1972, when the U.S. Supreme Court (Furman v. Georgia) held that the death penalty is "arbitrary" and "capricious." But just four years later, the court (Gregg v. Georgia) ruled that capital punishment does not violate the Constitution as long as there are adequate due-process procedures. This ruling opened the door for states to resume their use of the death penalty. In the two decades since Gregg v. Georgia, 40 states have instituted it for certain types of murder.

One of the states most eager to resume executions was Missouri. By the time I moved there in 1984, dozens of individuals had been sentenced to die. I was appalled. I wish I could say that I reacted by throwing myself (at least in some metaphorical sense) into the gears of Missouri's "killing machine." But the truth is that I acted on my moral outrage in a decidedly modest fashion. Following up on a notice in The Other Side, I contacted the Death Row Support Project for the name of a condemned prisoner with whom I could correspond. This is how I became acquainted with Samuel McDonald,  or #CP-17, as he's known in the Missouri correctional system.

Sam grew up in a poor, churchgoing family in St. Louis. At 17 he enlisted in the army and ended up in Vietnam. He proved to be an efficient soldier, earning a raft of medals. But the experience traumatized him, particularly when, in the process of "sweeping" a village, he killed an infant and an elderly woman; he had nightmares about this incident for the rest of his life. Like a host of other Vietnam veterans, he returned to the States mentally and emotionally unhinged, and addicted to drugs.

On May 16, 1981, Sam, high on "T's and blues" (a heroin substitute), robbed and shot Robert Jordan, an off-duty police officer, as Jordan and his 11-year-old daughter were leaving a convenience store. A poor African-American drug addict shoots a police officer in front of the man's daughter: that could easily have been enough to ensure that Sam would be condemned to die. But Sam was also assigned an assistant public defender who got into shouting matches with the judge. Worse, the judge refused to allow testimony regarding Sam's Vietnam experiences and their impact on his mental and emotional health, even though there was evidence that Sam was suffering from a classic case of post-Vietnam stress syndrome. (This failure to order a psychiatric examination would be at the heart of Sam's appeals over the next 16 years.) It was no great surprise, therefore, that on February 22, 1982, Samuel McDonald was sentenced to death.

Three years later, in 1985, I sent Sam my first letter. We soon became regular correspondents. I also visited him twice at the penitentiary in Jefferson City where he was originally held.

When I took a teaching job in Pennsylvania, I was no longer able to visit. So Sam began calling. He would call every two or three weeks, and we would talk from 20 to 60 minutes. We spent a good amount of time making jokes and ribbing each other; in fact, if Sam called when we had friends visiting, they would often be stunned to learn that, given all of the laughter, I was talking with a man on death row. We also spent a lot of time talking about sports. Both of us were convinced that we had special insights into the game of football. We had an annual contest to see who could pick the most winners in the college bowl games, with the winner--­usually Sam--receiving a "traveling crown" that Sam had made.

Of course, other conversations were much more serious. We talked about prison conditions, the status of his appeals and the Supreme Court. We talked about God, organized religion and the efficacy of prayer. We talked  about our families. I commiserated with him, when his son--who was three when Sam went to prison, and whom Sam always referred to as "Little Sam"--was caught in the middle of a gang fight, and was shot and paralyzed. Sam commiserated with me when my mother died of cancer. In fact, he was probably more sensitive to my grief than anyone outside of my family; in the weeks after her death he would call just to see how I was coping.

The point is that Samuel McDonald and I became close friends. At the beginning of our correspondence I thought that I would be the one giving to Sam. But it turned out that I was receiving much more from him than I was giving. Sam also befriended my wife and daughters, sending them birthday and Christmas cards and occasionally talking with them on the phone.

As time went on, and my friendship with Sam deepened, I tried not to think about the fact that the state of Missouri was determined to end his life. But in the spring of 1997, reality hit. Sam had run out of opportunities for appeal when the Supreme Court did not stay his execution, and the governor of Missouri  did not grant clemency. In other words, there was little reason for hope. Sam was given an execution date: September 24, 1997.

Sam handled these developments with remarkable grace, but I went into a severe emotional tailspin. I had begun writing to Sam out of my religious and political opposition to the death penalty. Now he was a close friend--and now he was going to be killed. But my personal anguish involved more than just Sam's impending death. I also agonized over what sort of friend I had been to Sam. In my mind, two shortcomings stood out. First, while Sam and I had frequently discussed religious faith, and while I had been forthright regarding my Christian convictions, I had not attempted and did not feel qualified to serve as Sam's "spiritual adviser," à la Sister Helen Préjean in Dead Man Walking. To compound my sense of failure, I could not bring myself to volunteer to serve as one of the witnesses to Sam's execution, even though I suspected that he wanted me to do just that.

During my time of distress, Father James Heft, chancellor at the University of Dayton (where I was now teaching), and Pastor Dorothy Nickel Friesen of First Mennonite Church in Bluffton, Ohio (our home church), provided wise counsel. Jim suggested that I directly encourage Sam to take steps to "make things right" with God and with the family of the slain police officer--advice which I heeded in a letter that I wrote Sam that summer. Jim also reminded me that friendship was itself a Christian virtue. Dorothy pointed out that Christ requires not heroism--of which I was in short supply--but faithfulness. I did not volunteer to watch Sam be killed. But when he asked if I would serve as one of his "family and friend" witnesses, saying, "I don't want to die alone, and I need to see you there," I said yes.

On the morning of September 23, 1997, my wife, Gayle, and I drove to the Potosi Correctional Institute, southwest of St. Louis in the Ozark foothills. Sam had called to tell me that I would be allowed to visit him before the execution, so when we arrived at the isolated, fortress-like prison, Gayle dropped me off at the front gate. A guard took me to Sam. We descended endless flights of stairs into the depths of the prison. This is where the "death cell" is located, where all death-row inmates spend their last two days of life. The guard knocked on the door and I walked in.

There was Sam, rumpled and weary-looking, and heavier than when I had last seen him. He was in a tiny cage with a bed, a chair, a toilet and not much else. Instinctively I walked up to the wire fence and put my hand against it, greeting him in the same way I had a decade before. But before Sam could respond a voice behind me barked, "Get away from there!" Alarmed, I looked at Sam, and he pointed to the floor; a white line marked off a "no-man's-land" between the rest of humanity and Sam's cage. I backed up behind the line and sat down in one of two chairs bolted to the floor. To my right, another guard sat at a desk, clattering away on a very loud typewriter, presumably reporting on what was taking place in the cell. A video camera recorded everything that was going on. Sam McDonald's final 48 hours were without privacy, in part to ensure that he did not commit suicide and thus cheat the executioner.

At first, given these conditions, I struggled to make conversation with Sam. But in a few minutes we were talking freely. In some ways it was no different from our phone conversations. We talked about sports and our families; we talked about our friendship; we even had a few laughs. But then Sam talked about himself: he regretted how he had messed up his life, and expressed remorse for what he had done. I later learned from the St. Louis Post-Dispatch that he had made a public apology in an interview with a reporter. He assured me that he was prepared to die ("things on the other side have to be better than they have been over here") and to face God. For the first time in the 12 years that I had known Sam McDonald, he was resigned to his impending death.

At 5:58 my escort returned. I stood up; Sam and I said, "I love you" to each other. The door opened, and I left the death cell. Soon after I departed, Sam ate his last meal, which included steak, catfish and eggs. Soon after that the prison authorities began to prepare him for execution.

At 10:30 I was searched, then ushered into a cramped waiting room with Sam's five other witnesses: his son, cousin, attorney, minister and another pen pal. There were also a few guards who were quite affable and had the courtesy to stay relatively quiet--except when they proudly recounted how they had built a sturdy ramp that would permit Sam's son to be wheeled into position to view his father's execution. For the next 70 minutes we sat around the table and talked about Sam. From his cousin and minister I learned about his childhood and his family. From his attorney I learned that Sam had good reason to have been optimistic about his appeals, given that he was a much-decorated veteran who had been denied the opportunity to present an adequate defense. With only a slight change in the circumstances of his trial and appeals, with only one small break somewhere in the process, Samuel McDonald might have spent a good deal of time, perhaps even the remainder of his life, in prison. He would not have been executed.

Suddenly the phone rang, and one of the guards answered it. He told us that the time had come, then warned us that "there will be no standing, crying out or knocking on the window," and marched us to our destination. The execution chamber was conveniently situated near the death cell, thus allowing for an efficient execution that did not interfere with "normal" prison life.

In Missouri there are three observation booths: one for the family of the crime victim, one for the state witnesses and one for family and friends of the condemned. The six of us were ushered into the latter, a tiny room that reminded me of a poorly appointed viewing box at a sports stadium. There was seating room for six witnesses in our booth, three in front and three in back. Squeezing into the booth with us were four guards, who flanked us on all sides, and who apparently were there to ensure that there would be no inappropriate emotional outbursts on our part.

I ended up in the front row, just inches from the viewing window; the blinds were closed, but through a crack I could see movement, and Sam's jaw and mouth. As I sat in that cramped booth, waiting and looking at the tiny fragment of my friend, I was overwhelmed by dread. As a middle-class, middle-aged white man who grew up in suburbia and has lived a secure and privileged life, I had never seen anyone die, much less be killed. Now I had a front-row seat. I would see Sam McDonald poisoned with a lethal combination of sodium pentothal, which would render him unconscious, and pancuronium bromide and potassium bromide, which would shut down his breathing and his heart.

Just after midnight the guards raised the blinds. There, in a dazzling white room, lay Sam. He was on a gurney with a white sheet up to his neck; from my vantage point, I could not see that he was strapped down, and that he was hooked up to a mechanical apparatus. Directly across from us was the booth containing the state witnesses (including journalist Christopher Hitchens, who wrote about his experience in Vanity Fair). I could not see the booth with the family of the murdered police officer.

Sam had obviously been briefed as to where his family and friends would be located, because he looked only at us. He was speaking rapidly, but we could not hear anything. I repeatedly mouthed "I love you" to him; others flashed the peace sign, or put their hands up in prayer. Behind me I could hear faint crying. Then, after a minute or two, the deadly drugs kicked in. Sam briefly shuddered. His eyes fluttered. And then he was still.

For the next few minutes we sat  looking at him. Then the guards shut the blinds and ushered us out of the observation booth and back into the waiting room. While we gathered our coats and belongings someone in our group suggested that Sam's minister lead us in prayer. But before he could respond, one of the guards hastily intervened: "We will have none of that in here." I wish now that I had defied this edict and dropped to my knees on the concrete floor; but instead, numbed by the horror I had just witnessed, I followed the escort out of the room, through the courtyard and beyond the prison walls.

Leaving Potosi did not mean that I could escape what I had seen. For 48 hours after the execution I felt an extreme compulsion to shower and shower and shower again. Eventually I realized that I felt filthy because I had observed an obscenity. Never in my life have I been so aware of the reality of evil as I was in that observation booth, watching the deliberate, methodical and antiseptic killing of Samuel McDonald, a killing done by the state of Missouri in the name of its citizens. For a long time I have known, intellectually, that capital punishment is wrong. Now I feel it--it's visceral.

I also learned something about what it means to follow Christ. I began writing letters to Samuel McDonald because I thought it was the easiest and safest way I could follow through on my convictions. Moreover, when it became clear that the state of Missouri was going to have its way, I desperately hoped that Sam would not ask me to witness his execution. Yet my tiny step taken in faith led me into deep and cold waters, where the grace of God sufficed to keep me from drowning, but not from feeling enormous pain, anger and despair.