It may seem somewhat peculiar to start a story about Tyson Gay, the double world sprint champion, in the San Francisco courtroom where Trevor Graham, the champion coach for drug-enhanced athletes, is on trial. But while Gay may never have met Graham, he is a curious product of Graham’s work.

In court yesterday, the jury was selected for Graham’s trial and opening statements were delivered by prosecution and defence. He is charged with perjury, for telling federal investigators that he had never supplied banned substances to his athletes. Given that his athletes include Marion Jones, Tim Montgomery and Justin Gatlin, he is arguably more responsible than anyone for dragging athletics to its present lows.

This is where Gay comes in. The United States AntiDoping Agency (USADA) has decided to use him to prove a point: that, contrary to slack generalisation, athletes are not all “on it” and that here is the champion of the world and he is Captain Clean. Effectively, USADA responded to Graham’s dirt factory by delivering a product from the opposite extreme with a label that reads: “I’m the one you can believe in.”

It helps that Gay is damned good. While Graham was in court yesterday, Gay was recovering in Los Angeles from an impressive 100 metres and 200 metres double against world-class opposition the day before. The idea is that kids can cheer him through the finish line safe in the knowledge that, if they stick his image to the bedroom wall, they will not have to rip it down next time the dope testers visit.

How can we be so sure? The answer is USADA’s “Project Believe”, under which Gay, and a small number of others, are blood and urine tested so often that a detailed profile of their chemical balance is built. Gay initially gave six test samples in a fortnight to establish his baseline profile; taking steroids now would skew the balance completely.This system is not infallible, but it does bring a new approach. Previously drugs tests have been there to prove whether an athlete, on a particular day, is guilty; this amounts to proof of consistent innocence.

Was he pressured into doing it? “Not at all,” he said. “I could have easily said no. And I do have to make time for it. But it was a simple question and a simple yes. I didn’t have to think about it. Is it fair that not everyone is doing it? It would probably cost too much. I don’t know if it’s fair, but it’s fair to me if that’s what I have to do to prove myself to people.”

The irony is that Gay is not actually a natural poster boy – for clean athletics or anything. He shrinks from publicity, has no desire to shoot his mouth or fan his ego. He is the polar opposite to your conventional, alpha-male sprinter – again, maybe no bad thing.

As if to make the point, when he took time out last week to discuss the responsibilities that come with being the figurehead of clean athletics, he took along his mother, Daisy.

This is crucial because the maternal relationship is unusually strong. Gay phones his mother every day, every night before a race and also an hour before his races, from the event warm-up track. Again, contrary to your Identikit sprinter, Gay does not have self-belief pumping through his veins; he suffers from extreme nerves and needs his mother to contain them.

Not surprisingly, she has had with him the conversation that one assumes most close parents would have with a child aspiring to the track. “We had it a few years ago,” she said.

“It was when the Gatlin stuff came out. His question to me was: ‘How do you compete with people who are cheating?’ I told him he will never have to rely on drugs as long as he relies on the scriptures. That was the extent of it. I told him, ‘Don’t you worry about those people.’ It’s just not a concern. He’s just good and clean.”

It is a shame, then, that more people do not know about him. He returned from the World Championships in Osaka last year with 100 metres and 200 metres gold and the sprint relay gold to boot, but as he said: “I can still walk the street. When I go home, I occasionally hear, ‘That’s the guy with the world record,’ even though I don’t have it, or, ‘That’s the guy from the Olympics,’ even though I’ve never been to the Olympics.”

His introverted personality clearly contributes here, though Jon Drummond, his coach, says: “He is funny, you just have to be close to him to hear it.”

Drummond, who perhaps had the loudest mouth of all in his sprinting days, is gently encouraging Gay to let his emotions go when he wins. The hope, then, is that he keeps on winning.

To do so, the key, Gay said, is “basically to forget about the three medals”. He thought that he was doing quite well in that regard until Drummond suggested otherwise.

“We had a conversation last week that really made me step up,” Gay said. “Jon told me, ‘I don’t really see the hunger in your eyes like last year. Understand that you don’t have any Olympic medals. Understand you haven’t earned greatness until you’ve won the Olympics.’ That bothered me because I thought I was training hard. I got offended.”

His performance in competition on Sunday would suggest that the hunger is back. He needs hunger anyway because, not happy with the three golds from last year, he is also considering the 4 x 400 metres relay this time and aiming at four.

That, surely, would have them stopping him on the streets. And it would give athletics a champion of which to feel genuinely proud. For here is a man not just running for himself but, to an extent, for the future of his sport.