LAUSANNE, Switzerland -- Former Olympic champion Roland Schoeman appeared by video link Monday at a Court of Arbitration for Sport hearing that could ban him beyond next year's Tokyo Games.
The World Anti-Doping Agency challenged a ruling by swimming governing body FINA to ban the 40-year-old South African for only one year after he tested positive for a black-market doping product.
The court said WADA has requested a ban of two to four years. A verdict is not expected for at least several weeks.
Schoeman competed at four previous Olympics. He won three medals at the 2004 Athens Olympics, including gold in the 4x100-meter freestyle relay.
The South African was training to qualify for the 2020 Tokyo Olympics when he tested positive for GW501516 last year. The substance failed medical trials and led WADA to alert athletes in 2013 that it was a threat to their health.
Schoeman denied doping and blamed contamination of the supplements he was taking.
His ban expired in May but he faces a longer sanction from CAS if he cannot prove the source of the contamination. A possible two-year ban, until May 2021, could still leave time to make South Africa's team for the postponed Tokyo Olympics.
In a ruling in a similar case Monday, Australian swimmer Shayna Jack was banned for two years for unintentional doping. An Australian sports tribunal previously recommended a four-year ban.