The Wall Street Journal reported on Saturday on the case of a Marine Corps colonel, V. Stuart Couch, who refused to handle the prosecution of a Guantánamo detainee, Mohamedou Ould Slahi, after concluding that the evidence he was asked to use to press the case had been secured through the use of torture.

In the following weeks, Mr. Slahi said, he was placed in isolation, subjected to extreme temperatures, beaten and sexually humiliated. The detention-board transcript states that at this point, “the recording equipment began to malfunction.” It summarizes Mr. Slahi’s missing testimony as discussing “how he was tortured while here at GTMO by several individuals.”

Funny how often this happens—DVDs disappear, videotapes can’t be found, and recording equipment malfunctions—whenever torture is in play. But the core of Jess Bravin’s well crafted story lies in how Couch came to realize he could no longer be silently complicit in the torture process.

In May 2004, attending a baptism at Virginia’s Falls Church, Col. Couch joined the congregation in reciting the liturgy. The reading concluded, as is typical, with the priest asking if congregants will “respect the dignity of every human being.”

“When I heard that, I knew I gotta get off the fence,” Col. Couch says. “Here was somebody I felt was connected to 9/11, but in our zeal to get information, we had compromised our ability to prosecute him.” He says, in retrospect, the tipping point came with the forged letter about Mr. Slahi’s mother. “For me, that was just, enough is enough. I had seen enough, I had heard enough, I had read enough. I said: ‘That’s it.’ ”

Couch asked that his objections be brought to the attention of DOD General Counsel William J. Haynes II. Of course, Haynes was the author of a notorious memorandum to Secretary of Defense Rumsfeld advocating the introduction of highly coercive interrogation techniques in Guantánamo in the first place.

Couch makes clear that his actions were not inspired by any sense that Slahi was innocent. To the contrary, Couch felt he had “blood on his hands.” “I’m hoping there’s some non-tainted evidence out there that can put the guy in the hole,” he says.