He was at Abu Ghraib. He helped government investigators put together the pieces of the abuses that occurred there. And in the insular field of military intelligence gathering, that almost cost him his career.
But Nelson has a mission: He wants to bring interrogation out of the shadows - to make it a profession that can be spoken about in polite company. At Westminster College on Monday to speak to students and staff about his misunderstood profession, Nelson said legal reforms that came about in the wake of the Abu Ghraib scandal are a good first step.
"There's plenty of oversight now," said Nelson, a native Utahn who has worked in Bosnia, Iraq, Afghanistan and Guantanamo Bay, Cuba. "So we've gotten beyond brutality - the next step is getting beyond mediocrity."
His plan: Gather the best interrogators from around the world into a fraternal, professional organization that would lobby for appropriate oversight, high standards and a code of conduct.
And that's likely to be yet another uphill battle.
He explains by talking about his experiences at Fort Huachuca, where he taught interrogation techniques to soldiers at the U.S. Army Intelligence Center and School.
"In the past, it didn't matter what kind of student you were, how good your test scores were - if one of the senior interrogators said you didn't have what it takes, you were gone," Nelson said. "But when I was teaching there, there were students saying, 'I really don't want to be here, sir, is there some way I can get out?' "
Nelson rails against poor standards, ineffective training and the use of part-time soldiers for a job that, in what he believes would be the best scenario, should be done by those who can make longer and more frequent combat tours.
It wasn't too long ago that Nelson was considering throwing in the towel. In the winter of 2005, he'd gone a year and a half without work - the result, he believes, of being blacklisted among those who didn't appreciate his public denouncements of cruel practices and his participation in the military's investigation of Abu Ghraib.
But David Irvine, a retired brigadier general who taught prisoner interrogation for the U.S. Army Reserve, said the gospel Nelson was preaching was the hard truth. He said it's unthinkable that someone with Nelson's résumé would have been excluded from working in the field of interrogation.
"If I were running a private company fielding interrogators to work in the Middle East, right now, Torin is exactly the guy I would be looking for," Irvine said. "He's very, very good. He's already proven he knows what he's doing - and that he knows where the line is and that he's not going to cross it."
Irvine said that's among the most important traits for an interrogator - particularly as the U.S. military seems to be learning that brutality can't win a battle against an insurgency.
"I think there has been a real sea change in the way virtually every entity that is involved in intelligence gathering, and particularly interrogation, comes to the table now," said Irvine. "I really believe that all of the attention that was focused on Abu Ghraib and on torture has made everybody very, very cautious."
And that seems to have revived Nelson's career. In the past two years, he's done two tours of duty as a civilian interrogator for the military in Afghanistan. He's a frequent speaker on the subject of professional interrogations and is working on a book about his experiences. And he's working to found the Society for Professional Human Intelligence, which he envisions as a lobbying group that would set standards and fight for the interests of those who share his vision of interrogation.
It's a vision he knows that not everyone can see right now.
"In a democratic society that believes in the rule of law and has support for human rights, we shouldn't be ashamed of the fact that we have interrogators, we should be proud of that fact," Nelson said.
And if that means getting out from behind the security of the shadows, Nelson said, so be it.