At forty-three years old, Kevin Castille is now the second-oldest American male marathon-trial qualifier ever. PHOTOGRAPH COURTESY KEVIN CASTILLE

Throughout his twenties, Kevin Castille sold crack cocaine on the streets of the Truman neighborhood in Lafayette, Louisiana, where his grandparents and aunts had raised him and eight other children, who slept in their modest family home three to a bed. He'd been the smallest, quietest one. He still was. But dealing brought money—some ten thousand dollars a week, throughout the nineteen-nineties, in profits. He bought fancy clothes and cars, including a string of seven Ford Mustangs. He didn't use drugs—or even drink alcohol—but he was "getting high from the cash," he told me a couple of years ago, for a Runner's World profile. Living in a bleak blur of hotel rooms and apartments, he'd had two daughters with two women by 1997, when he turned twenty-five. Just as his own parents, an alcoholic and a troubled Vietnam veteran, had been absent from his life, he was largely missing from his children's.

He survived this way, under constant threat of arrest and violence, until 2001, when he was sent to prison for possession with intent to distribute. Confinement was something of a relief: junkies and robbers couldn't get him inside. It was also a wake-up call. Castille had been the leader of the Acadiana High School cross-country team in Lafayette—they finished second at state during his senior year—and had even been recruited to run at the University of Louisiana at Lafayette, where hunger had led to hustling after a single season. Now he’d lost some of his most important years as a runner. His running career before the age of thirty boiled down to three words familiar to most serious runners: "did not finish."

This week, the forty-three-year-old high-school track coach, personal trainer, and father will run in the U.S. Olympic marathon trials held in Los Angeles. Over the past decade and a half, Castille has resurrected himself as a man and a runner and made his mark in the masters category at an impressive range of distances. (For distance running, masters runners are over forty years old.) He has held American masters records at the three-thousand-metre, five-thousand-metre, ten-thousand-metre, and ten-mile distances, though only his ten-thousand-metre record remains. These results, he says, are due to both hard work (he runs 120 miles per week, including brutal track workouts texted to him by his coach, Matt Lonergan, an assistant coach at Northeastern University, in Boston) and the unexpected benefit of not running in his twenties: his legs—if not his mind—are less weary than most. "I was Lazarus," he told me, describing this period. "I'd been risen from the dead." (This period was not without its own pitfalls: he qualified for the ten-thousand-metre race at the 2004 Olympic trials, but didn't finish.)

Some observers, particularly those who frequent the speculation-friendly LetsRun message boards, claim that his running transformation couldn't possibly have transpired without the assistance of performance-enhancing drugs. But Castille has never failed a test. The only advantage he says he has allowed himself: regularly sleeping inside an altitude-simulating tent, where he inhales the reduced oxygen levels that would be available at ten thousand feet, prompting him to produce extra red blood cells. The idea is to counter the low elevation of Louisiana. "It's not a runner-friendly state," he said. "Too much heat and humidity. Not enough hills or elevation. But it's my home and I'm not leaving."

As if he had not had enough challenges already, Castille had to qualify twice for this year's Olympic marathon trials. He was told that he'd made the cut back in May of last year, at a San Diego half-marathon, with a time of 1:04:45, and began to receive paperwork from USA Track & Field reaffirming as much. But he learned in December that the San Diego course was ineligible, because there was too great an elevation drop per kilometre. A few weeks later, in Jacksonville, Florida—just six weeks before Olympic trials would begin, only nine weeks into his marathon training—he requalified with an even faster time, two seconds off his half-marathon best: 1:04:33. "I didn't panic," he said. "I knew I was fit." He's now the second-oldest American male marathon-trial qualifier ever (and the oldest this year); he'll turn forty-four in March.

Age, geography, Olympic trials: these are relatively minor concerns compared with Castille’s past. It wasn't until last year that the faculty, students, and parents at Lafayette's St. Thomas More high school, where he is the beloved track coach, learned the darker details of his biography. "I work in the Catholic system," he told me. "In the Catholic diocese, where people say, 'Come as you are. God's gonna save you no matter where you come from.' But I wondered: Would people really do what they say they'd do? People know me and they know what I do here, my involvement in the community and dealings with kids. And all of sudden, after all these years, they learn this stuff about drugs and jail? I'd kept it in a safe with a lock and key. What would people's perceptions be? It took years and years to forgive myself for what I did." It took the Lafayette community—most of it, anyway—no time at all.

On January 17th, Castille set a course record at the Louisiana half-marathon: 1:07:53. He believes that he will soon run twice that distance at the same pace. Sure, he's never run a marathon quicker than 2:20:58 (in 2013, at Minnesota's Twin Cities marathon), but he thinks two hours and fifteen minutes is reachable, and he feels the same about the Rio de Janeiro Olympic games, in August. Considering the Benjamin Button arc of his running life, it's hard to doubt him. But should he fall short of the Olympics, he has the joy of coaching high-school cross-country to fall back on. "The team is doing awesome," he recently told me. "I had my best team this year. The state course was so muddy, in November, it kind of neutralized us. We got third. But that's just the way life is. It's a life lesson for the kids."