In The Uninnocent (Farrar, Straus and Giroux, Nov.), law professor Blake reflects on a teenage family member’s incarceration for murder and the heartbreak it caused.

How did your cousin’s case and his prison experiences shape your view of the law?

It happened in the summer of 2010, and I went back for the second year of law school that fall. I took Juvenile Justice, and I started teaching at a juvenile detention facility. It wasn’t exactly a conscious set of decisions, but you can see so clearly, looking back, that it had everything to do with this murder. But it also created this huge jagged edge of disillusionment. Because I couldn’t participate as fully in the farce of law school when my cousin’s trials were happening, and I was just seeing a whole lot of destruction and devastation.

You explain that in rare cases, mandatory life sentences for juveniles may be “fair,” but they’re never “just.” What’s the difference?

I think fairness is almost mathematical. Or it’s really practical; I imagine two sides of a weighted scale. And we use the imagery of the scale in justice, and in criminal justice, all the time. But I think that true justice—moral justice—can’t end there, because life is so much more complicated than that. If we want to rise to the highest versions of ourselves as human beings, we have to have a system that does more than “an eye for an eye,” especially when you’re talking about the lives of children.

In the book, you write that “no one deserves mercy, and that is its whole point.”

We err as people, and we trespass, and we transgress, and we sin, from a theological perspective, and God gives us God’s mercy. And as people, down in the muck and mud of this world, we have that same opportunity to extend mercy to one another. But the only time mercy comes into play is when someone has done something “bad,” or wrong—in this case, very, very wrong. I really don’t want to minimize the crime. I want a second chance for my cousin, but I’m also really cognizant of the fact that a lot of people don’t want that for him. And I cannot tell them that they are wrong, because they lost their child. But I do know that mercy belongs to the undeserving. That really feels like a truth you can’t get around, especially as a Christian. So when you go into these largely Christian southern states that have these extremely punitive criminal justice systems, and everyone is doling out these extreme sentences—these literally merciless sentences, to young people—and talking about Jesus out of the other side of their mouth, it’s so frustrating, to put it mildly.