On Sept. 11, 2001, Marine Lt. Col. Stuart Couch's friend died co-piloting the second plane to hit the World Trade Center. Soon after, Couch became one of the first military prosecutors assigned to the U.S. military base at Guantánamo Bay to prosecute men alleged to have carried out the terrorist plot. He ultimately would refuse to prosecute one detainee: Mohamedou Ould Slahi. "It became clear that what had been done to Slahi amounted to torture," Couch says. "Specifically, he had been subjected to a mock execution. He had sensory deprivation. He had environmental manipulation, that is, cell's too cold or the cell is too hot ... He was presented with a ruse that the United States had taken custody of his mother and his brother and that they were being brought to Guantánamo." Couch says he concluded Slahi's treatment amounted to illegal torture. "I came to the conclusion we had knowingly set him up for mental suffering in order for him to provide information," Couch said. "We might very well have a significant problem with the body of evidence that we were able to present as to his guilt."