Gatlin says he's mystified why he tested positive for testosterone or other steroids after a relay race in Kansas in April.
It's the second drug test the 24-year-old has failed. He was suspended for two years in 2001 after testing for illegal substances, the result of taking medication to control attention deficit disorder.
But his coach insists he is the innocent victim of a set-up.
"We are 100 per cent sure who it is," said Trevor Graham.
"The individual that did it, it's an individual that we fired and we went back and hired ... he came to the Kansas relay and was (upset) with Justin."
While Gatlin waits to hear his fate, the leader of the World Anti-Doping Agency called for him to be thrown out of the sport.
"He needs to be banned for up to life," said Dick Pound.
"There may be some extenuating circumstances to come out but I think if he just continues to come out with some bland denial that 'I never did anything, I can't imagine how this result occurred,' that will not help him when it comes to sentencing.
"If they can find someone who did, in fact, spike it, then it is for them to prove but short of something like that I think he has a very serious problem."
While Gatlin has consistently lobbied for a drug free sport, his connection with his coach is proving controversial.
Graham is reportedly under investigation for his role in the Bay Area Laboratory Co-operative (BALCO), which has been linked to steroid cases involving professional baseball players and track and field athletes.
If Gatlin is proven guilty, he'll also be stripped of the 100m world record of 9.77 seconds he jointly holds with Jamaican Asafa Powell.
The story has become front-page news in America as sports fans were still reeling from the news that America's Tour deFrance champion Floyd Landis had tested positive.
"First, the winner of cycling's premier race. Two days later, the winner of track and field's signature event,” wrote the Chicago Tribune.
"Never has the credibility of sport been more undermined by doping, nor has the morality of leading US athletes been more called into question."
"This does raise the issue of what we teach kids about ethics and sportsmanship," Merrill Melnick, a sports sociologist, told the Tribune.
"Perhaps we need to take a look at the whole U.S. sports system. Perhaps there is a poison corrupting everything."
"Hard to believe: Credibility is Tested Again.” was the New York Times' head line played over two stories, the news account of Gatlin's positive result and a column noting that Landis's protestations of innocence beggared belief.
"Deception fatigue has its limits" the paper continued.
"At some point, fan endurance for athletes’ tall tales will expire. Only then, with good faith and gullibility exhausted, will the truth be a priority."