Lieutenant Colonel Stuart Couch, a military prosecutor at Guantanamo, truly believed that Mohamedou Ould Slahi was guilty, but he also believed Slahi’s interrogators should face prosecution for torture.

Jess Bravin writes: It would be months before Stu Couch got a fuller picture of the Slahi interrogation. But as he began to piece together the facts, he became increasingly alarmed. Each detail suggested a sustained, systematic regime of physical and psychological coercion that undermined the reliability of everything Slahi said. The trial could end up being more about what the government did to Slahi than what he did for al Qaeda.

Couch was convinced that Slahi had spent years organizing the Qaeda network in Europe, culminating with recruitment of the Hamburg cell that supplied hijackers for 9/11. If any detainee deserved the death penalty, it was Slahi.

Yet Couch hesitated. He ruminated for weeks. Was the United States justified in beating Slahi, in subjecting him to isolation, sensory deprivation, temperature extremes, and sexual humiliation? Was it justified in constructing elaborate scenarios that literally put the fear of death in him, convincing him that he was about to be killed?

One threat, Couch believed, was the worst of all: To have his mother raped.

“Military guys are real big about their mommas,” Couch said. And few more than Stu Couch. “Other than my wife, my mom is my best friend,” he said. “That’s just who I am.”

Couch wondered if he could prosecute Slahi at all.

He would lie awake for hours almost every night. During the 10-hour workdays at commissions, dark circles under Couch’s eyes exaggerated his hangdog look.

One Sunday, as usual, Couch drove his family to church. He was distracted as the service unfolded, possessed by the Slahi case. He mechanically obeyed when the minister called on worshippers to stand.

“Will you seek and serve Christ in all persons, loving your neighbor as yourself ?”

“I will, with God’s help,” came the echo. All persons. That included Osama bin Laden. And Mohamedou Ould Slahi.

“Will you strive for justice and peace among all people, and respect the dignity of every human being?” Every human being.

He was surrounded by people, but suddenly Couch felt very, very small. It was as if he stood alone in a dark, cavernous hall, a bright, single shaft of light illuminating him, unseen persons, or powers, awaiting his answer.

“I will,” he said. “With God’s help.”

After the service, he told his wife, Kim, of the threat to rape the prisoner’s mother. It was the linchpin to the prisoner’s cooperation, the foundation of the entire case.

He told Kim he would have to drop a case. A 9/11 case. “I hate to say it,” he said, “but being a Christian is gonna trump being an American.”