British athletics faces an anxious time when the trial of American sprint coach Trevor Graham opens in California on May 19. It threatens to punctuate the run-in to the Beijing Olympics with further revelations of drug cheating.

A Texas-based Mexican, Angel Heredia, will be a key prosecution witness in Graham's trial. In an attempt to discredit him, Graham's lawyers will name 12 drug-using athletes, clients of Heredia's, who have won a combined total of 26 Olympic and 21 World Championship medals, up to 2004.

One of those, it was alleged yesterday, is Maurice Greene, the former Olympic 100 metres gold medallist and world record holder.

A former Mexican discus champion who describes himself as a chemist, scientist, and nutritionist, Heredia claims to have identified to prosecutors some two dozen elite athletes in the hope of remaining a federal witness rather than become a prosecution target. He says he supplied illegal drugs and advice to Graham and his athletes, and many other sprinters and coaches who may now be called to testify.

Claims in US newspapers don't specify the nationality of any other athletes, but the very first exposed as a consequence of the Bay Area Laboratory Co-operative scandal, which triggered a domino rally of falling athletics stars, was Britain's former European 100 metres champion, Dwain Chambers. Those who followed included Marion Jones, former world record-holder Tim Montgomery, and double world sprint champion Kelly White. Now there will be an anxious wait to see if other Britons are involved.

The Balco affair was triggered when Graham himself sent a sample of a designer steroid to the authorities. Yet, after several of his own athletes had been named as cheats, inlcuding Olympic gold medallist Justin Gatlin, UK Athletics later approved at least one young athlete being sent to train with Graham.

The coach, charged with making false statements to federal agents, says he is innocent, and that Heredia is trying to divert attention from his actions.

In recent interviews with The New York Times, Heredia has detailed records that appear to link him with many of the world's best sprinters. Those include cancelled cheques, telephone recordings, shipping records, laboratory readings of blood and urine samples, and Justice Department documents. The paper cites a copy of a bank transaction showing a $10,000 wire transfer from a Maurice Greene to a relative of Heredia; two sets of laboratory reports with Greene's name and age on them; and an e-mail message from a close friend of Greene, attaching a lab report, and saying: Angel, this is Maurice's results, sorry it took so long.' The allegations could not have come at worse time for the IAAF, who recently named Greene an ambassador.

Greene expressed sympathy for Chambers in his fight to re-establish himself when we spoke at last month's World Indoor Championships in Valencia. "If you get busted, you should get banned for life," he told The Herald, "but under the rules, in Dwain's case, he's paid his penalty, taken the punishment they've given him."

Greene is currently doing consultancy work and has a music company, Mo Greene entertainment. "I'm not doing any coaching . . . We all want to see a clean sport - and the sport needs as much positive energy as we can give. The sport's taken a lot of hits. A lot of negative things have been happening, so now it's time for athletes to step up, let their personalities come out and put on a great shows for people. That's what this sport needs."

He also said he felt sorry for Jones: "I think a lot of athletes just make bad decisions."

If the names of sprinters claimed to have worked with Heredia don't emerge in court, they can still be pursued by the US Anti-Doping Agency.

Greene, double Olympic gold medalist and a five-time world champion, has never failed a drug test.

Jones also never failed a test, but she is in jail. And last week members of relay squads in which she ran were stripped of their Olympic 2000 medals.