At the Death House Door is a solemn inquiry into the execution of Carlos De Luna, seen through the eyes of Pastor Carroll Pickett. De Luna was a Mexican American convicted of murdering gas station attendant Wanda Lopez in 1983 in Corpus Christi, Texas. As has been happening lately in many capital punishment cases, doubt has been cast over whether De Luna was actually guilty of the murder.

Pastor Carroll Pickett counseled the inmates of the "Walls" prison unit in Huntsville, overseeing nearly 100 executions, including the world's first lethal injection. Having lost two upstanding members of his congregation during a hostage crisis at the prison, he was a strong advocate for the death penalty when he joined the unit. But years of counseling the inmates, getting to know them as human beings, and discovering that victims' families seldom got any sense of closure from the executions, took their toll on Pickett. Alienated and lonely, he confessed his private thoughts into audio cassettes after each execution. By the time he met convict Carlos De Luna, he had begun to oppose the death penalty.

Of all the inmates that claimed their innocence to Pickett, none had struck him as more genuine than De Luna. De Luna's arrest was made with very little evidence, and another convict, Carlos Hernandez, who was a virtual lookalike, even bragged about how De Luna was convicted for someone Hernandez had actually killed. Even a knife resembling Hernandez's distinctive one had been found at the scene. Frustrated at the futility and injustice of the executions, Pickett quit and became a dedicated anti-death penalty activist in Texas, an uphill battle if there ever was one. Texas leads the country in executions, ahead of second-place Virginia by more than 4 to 1 since 1976.

Through the investigation by Steve Mills and Maury Possley, two Chicago Tribune reporters, into De Luna's arrest and its inconsistencies, the filmmakers were led to De Luna's final confidant, Pastor Pickett. Directors Steve James and Peter Gilbert (directors of Hoop Dreams) give us a grim but fascinating look into the tortured soul of Pastor Pickett. Pickett's father, bitter over his own father's murder, was influential in forming the pastor's opinion of the death penalty in his youth. Raised to keep his emotions in constant check, he would record his misgivings after each execution, amassing a collection of 95 tapes over the years. But his daughter recalls the one time anyone in his family saw him weep, screeching as he collapsed to the floor, while his then young daughter helplessly looked on.

Gripping and intense, the documentary gives a fair-minded look at capital punishment, and one man's mission to find a better alternative.

IFC presents At the Death House Door Thursday, May 29 at 9 PM ET.