So have other known dopers - the most common way they are caught is by mistakes on their parts, such as being caught with the evidence... or having others testify against them. The latter is true in Armstrong's case - numerous (10 or more) former team mates have all testified against.
He also failed one drugs test - he then retroactivly got a doctor's note to explain it away.
old samples of his were retested... and found to contain EPO.
USDA has stated his blood samples from 2009 and 2010 were "fully consistent" with blood doping.
Those aside, he's never failed a test.



And WADA is on USADA's side, WADA is generally see as having much more credibility - not elast by not being run by someone who was banned from the Olympics during his own cycling career and has a reputation for being soft on doping. Of course there is also the fact that officials in the UCI are implicated in the charges (I belive UCI have been asked to supply McQuaid’s exchanges with Armstrong by USADA).

Armstrong has taken the least worse option - concede a fight he can't win, so he doesn't have to go under oath and lie... and hope it means that no one brings out the evidence against him so people can parrot the "we've not seen any evidence, so it is a witch hunt line". With luck Bruyneel will still fight the charges so the evidence will come out despite Armstrong's attempts to dodge the one fight he can't bully his way out of.



Look up Greg LeMond.