LAUSANNE, Switzerland — Spanish cyclist Alberto Contador arrived Monday to fight a bid by cycling's governing body to impose a doping ban which could strip him of his 2010 Tour de France win.
Wearing a white shirt and dark suit and surrounded by his lawyers, the cyclist entered the CAS 20 minutes before the hearing which is to last until mid-day on Thursday. He declined to address the media.
The Spanish Cycling Federation (RFEC) initially cleared Contador of any wrongdoing after he claimed his sample had been contaminated by a steak which he ate on the second rest day of the 2010 Tour de France.
That ruling allowed Contador to continue competing, but the International Cycling Union (UCI) and the World Anti-Doping Agency (WADA) filed appeals to CAS.
The hearing at CAS will take place behind closed doors and the court has said that it will "issue its decision with reasons as soon as possible but probably not sooner than several weeks following the completion of the hearing".
A file of some 4,000 pages is being examined by the court chaired by Israeli lawyer Efraim Barack, who is assisted by Swiss Quentin Byrne-Sutton and German Ulrich Hass.
More than 20 witnesses are expected at the hearing.
At the heart of the case is the 50 picograms of clenbuterol, found in his urine on 21 July 2010, during a rest day of the Tour de France at Pau.
Although known as a powerful drug used to treat asthma, clenbuterol can also help build up lean muscle mass and burn off fat.
Contador's lawyers argue that he was contaminated by a steak consumed the previous evening and which originated from his native Spain.
His defence will say that even if the anabolic agent used to boost cattle growth has been banned in the European Union, there remains the possibility that it is still being used by some.
The Spanish Cycling Federation bought the argument and in February cleared Contador of all charges.
However, the UCI and WADA were not convinced and decided to file an appeal at sport's highest court -- CAS.
WADA and UCI have so far remained tight-lipped about the evidence that they would be putting before the CAS.
If CAS upholds the appeals by the UCI and the WADA, the Spaniard faces a competition ban and being stripped of his 2010 Tour de France title and the Giro d'Italia, which he won for a second time this year, and any other victories since July 2010.
Contador has insisted that he has never taken banned drugs, even going as far as to pass a lie detector test to prove his innocence.