Lance Armstrong has stepped up his attack on the US Anti-Doping Agency, saying the credibility of its case against him has been undermined by the fact that two key witnesses are self-confessed dope cheats. Armstrong, a seven-time Tour de France champion, questioned the credibility of Floyd Landis and Tyler Hamilton, his former teammates, in a letter to USADA from his lawyer dated Wednesday and obtained by The Washington Post. USADA is hoping those two witnesses can help prove Armstrong used performance-enhancing drugs during his career. Both have both accused Armstrong of doping. The letter from Armstrong's lawyer Robert Luskin says the agency's alleged evidence against Armstrong includes previously disclosed Landis emails and a 2011 television interview with Hamilton.
 
"USADA has no regard for its own protocol, fairness or common notions of decency," said the letter. Armstrong's lawyers are trying to discredit any evidence USADA tries to use from Landis and Hamilton, arguing that Landis is an admitted liar. USADA has said previously that at least 10 former Armstrong teammates and associates would testify against him, but vowed to keep the names confidential. A three-member independent anti-doping review board is charged with considering evidence against Armstrong to see if there is enough of a case to push forward with formal charges and a hearing.  If USADA files charges against Armstrong, a three-person arbitration panel could start considering Armstrong's case by November. Armstrong would be allowed to review the USADA evidence in advance and cross-examine any witnesses against him. Armstrong has always insisted he is innocent, saying he has passed more than 500 drugs tests.