Floyd Landis' lawyer has accused the anti-doping authorities of failing to meet international testing standards in the case against his client.
Suh attacked the testing lab's competence and integrity
Last year's Tour de France winner faces a two-year ban if found guilty of doping at a US Anti-Doping Agency disciplinary hearing in California.
A Paris laboratory found traces of testosterone when Landis was tested after stage 17 of last year's Tour.
But lawyer Maurice Suh said testers were incompetent and bungled the test.
Landis himself has yet to speak at the hearing but told reporters outside Pepperdine University's School of Law that he was "excited to get the case under way" and was hopeful of being confirmed as Tour champion and returning to racing.
In the opening exchanges of the hearing, Suh told the three-man panel that the French lab failed to meet "international standards" and called the whole case "an embarrassment."
But USADA's lawyer Richard Young defended the lab, saying the test results were backed up by extensive evidence, and had been independently confirmed.
He said Landis had "bet the house" that a second round of tests would prove him innocent, and "he lost the bet".
The hearing concludes on 23 May.