Three years ago, after several prisoners on Illinois's death row had been exonerated, Gov. George Ryan named a commission to study the effectiveness of capital punishment. Scott Turow was invited to serve, not only due to his fame for courtroom thrillers like "Presumed Innocent," but because the former prosecutor had successfully defended an innocent man who had spent 12 years on death row for the murder of Jeanine Nicarico. Three prosecutors in that case were later indicted. Turow's experience on the commission changed his mind about the death penalty, and resulted in his 2002 novel "Reversible Errors," and the just-published nonfiction account, "Ultimate Punishment." We spoke to Turow recently about the morality of the death penalty.

How did the governor's commission convince you that the death penalty was wrong, when the Nicarico case didn't?
You'd think it would have convinced me, but I was still relatively close to my experience as a prosecutor, and I also thought, with prosecutors that wanton, it didn't prove there was something wrong with the death penalty, it proved there was something wrong with the prosecutors. It was only as time wore on in Illinois and Anthony Porter and Gary Gauger and others were exonerated that it started to dawn on me that innocence was actually a problem among those on death row.

How many people in Illinois have been exonerated?
You can look on the Death Penalty Information Center for the latest number. Last time I looked, we've executed 1500 people and exonerated 108--that means legally absolved. There are also dozens and dozens of cases where the charges were resolved without a formal finding that they were baseless. I've never been under the illusion that everybody on death row is innocent-far from it. My own guess is upwards of 90 percent are guilty. But a ten percent error rate if that's what it is, or even five percent, is really way too high.

Have you met any of the death row inmates who have been exonerated and released?
Sure, many of them.

I'm always amazed at how forgiving they are.
It really varies from guy to guy. A lot of them develop a sense of religious belief. Imagine if you were sitting in a prison cell for ten years, asking."Why is this happening?" You've got to believe that somebody has a reason for this, and it's certainly not a human one. But both the degree of recovery and range of response varies. Obviously, in the abolitionist community they want to present everyone as a Christlike martyr. I think to some extent that's p.r.

Did your religious background affect your feelings on this issue?
I'm of that generation of Jews still deeply influenced by the Holocaust. Certainly the notion that the state power to kill can be subject to such extraordinary abuse is always lurking beneath the surface for me. Certainly my experience and identity as a Jew is there. I wouldn't say religious training contributes a lot. A rabbi was upbraiding me for claiming that the Yahweh of the Old Testament is a wrathful God. With all due respect to the rabbi, I think he's wrong. I think that's a fair view of most of what that God is up to.

So is capital punishment revenge?
It's subtly different than revenge. I always laugh when people say, "It's not just revenge." That's a religious attitude among those who have been taught to turn the other cheek. Revenge obviously plays a large part in punishment. Prisons wouldn't be as stark and awful as they are if we didn't want a measure of revenge. If we were just trying to keep them off the street, they could live in college dormitories.

So what are we doing when we sentence people to death?
I think to most Americans it's a statement of values. For ultimate evil there has to be ultimate punishment. Certain behavior--McVeigh, John Wayne Gacy, the Beltway Sniper--is so far beyond the bounds of what can be tolerated in any civilized society that we have to demand the highest price imaginable. That's the argument: to do less demeans the value of life and what it means to live among each other.

Do prosecutors become calloused to the value of life? Is that how they come to push for death even when they have the wrong person, as they did in the Nicarico case?
I don't think the Nicarico prosecutors can be confused with all prosecutors. To an extraordinary extent we are still sheltered from the reality of what goes on. Sitting in the back of a felony courtroom in Chicago, you hear stuff that blows your mind. You've got routine drug deals that are to some extent explicable and understandable. But the student who goes in to the nun who taught him and pours lye down her throat, or the father who takes his house keys and puts out his child's eyes-these are people who have been raised in hideous circumstances that have taught them no sense of human attachment who behave that way. They don't have feelings for other human beings. They can be cruel in ways that it's hard for you and me to imagine.