On the warm May evening when the state of Tennessee executed Don Johnson for having murdered his wife, Connie, in 1984, there were two demonstrations taking place outside Riverbend Maximum Security Institution. Prison officials fenced off the area around the perimeter, and in a surreal moment that is part of death penalty vigils whenever an execution takes place in Tennessee, a correctional officer, dressed head to toe in tactical gear, asked, as if he were separating the guests at a wedding, if we were for or against the death penalty. He then directed us to the appropriate part of the field.   Technically, I’m neither. I am a reporter who, for the last few years, has been covering the death penalty for Mother Jones. I’ve spoken to activists and experts. Once, I interviewed an Alabama death row inmate a few days before he was executed for a murder he insisted he didn’t commit. After he was put to death, a friend texted me: “Wow, your guy is gone,” suggesting a personal connection to him that I confess our conversation had created. I remember his thick Southern accent, the intensity with which he was making his case as if I could make a difference, and the haunting realization t...