Seven-time Tour de France champion Lance Armstrong asked a US Anti-Doping Agency review board to dismiss "spurious" allegations brought against him last week.
Armstrong's attorney Robert Luskin replied to USADA's claims that the famed US cyclist was part of a doping conspiracy in an 18-page letter obtained by the Washington Post and linked to Armstrong's Twitter account.
Luskin said USADA had not submitted proper evidence to support its claims that Armstrong was a dope cheat.
"USADA has submitted no evidence to support its spurious allegations," Luskin wrote.
"USADA must either submit the evidence it relies upon in its June 12 letter (accusing Armstrong) or the review board should summarily recommend that this matter be dismissed for lack of sufficient evidence."
Lawyers had asked USADA for its evidence but were not provided with details of the case assembled against Armstrong, they had said.
"To permit USADA to proceed without sharing its evidence would violate not only the clear language of the protocol but also our shared concepts of justice and fair play," Luskin wrote.
The three-member board is the USADA panel charged with considering evidence submitted by the organization and those it targets and judging if there is enough of a case to push forward with formal charges and a hearing.
If USADA files charges, 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.
Such a case could end up at the Court of Arbitration for Sport and could result in the stripping of Armstrong's Tour de France titles and a life ban from competition if he is found guilty, although he has retired from cycling.
Armstrong has steadfastly denied doping allegations for many years and a US Justice Department investigation into doping claims was halted in February with no charges brought against him.
While former Armstrong teammates Tyler Hamilton and Floyd Landis have publicly accused Armstrong of doping, USADA has not revealed its witnesses against the US cyclist, whose comeback from testicular cancer has made him a hero in the eyes of many.
Luskin said Armstrong's camp would "urge the review board to prevent USADA from emasculating its own protocol and the review board process."
There are no positive doping tests against Armstrong, two notable allegations against him having been successfully refuted years ago.
"The two specific and recycled allegations that (USADA) identifies have been thoroughly and publicly discredited," Luskin wrote.
"USADA has refused to disclose anything else, such as an expert analysis substantiating its unsupported view of these (doping tests).
"The review board cannot possibly carry out its obligation to evaluate USADA's case if USADA refuses to disclose its evidence."
Luskin argues that USADA "has based its charges on admissions or witness testimony and not on a positive result.
"That it refuses to accord these same basic rights to Mr Armstrong is a disgrace and highly probative of USADA's readiness to employ unlawful tactics and questionable practices in its zeal to punish Mr Armstrong at all costs."
Luskin wrote that USADA attorneys are ready to continue chasing Armstrong even if the review panel does not push forward with formal charges.
"Its general counsel has already advised us that USADA may ignore what the review board recommends and continue its obsessive pursuit of Mr Armstrong, even if the review board finds no evidence on which to proceed," Luskin wrote.
"USADA's overly expansive view of its own authority -- not to mention its smug self-regard -- undoubtedly explains its threadbare charging document, its arrogant and even craven refusal to disclose its evidence and its complacent expectation that the review board will not hold it accountable."
In pressing the attack upon USADA, Luskin wrote the board's review "should include careful scrutiny of the conduct of USADA to determine whether its officials violated federal law and the World Anti-Doping Agency code in securing testimony against Mr Armstrong."
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