> My understanding is also that currently no tests have ever returned a positive for him True. However, consider the following anecdote: The most prominent d

> My understanding is also that currently no tests have ever returned a positive for him True. However, consider the following anecdote: The most prominent doping agent in professional cycling during the 1990s, erythropoietin, was undetectable for a long time. Eventually in 2000 a test that could distinguish the endogenous and pharmaceutical versions of the hormone. But even then, all that needs to be done to render this test ineffective is to come up with a way to produce a synthetic version with the same chemical structure as the natural one. So there's that. And there's the amount of money wrapped up in doping in professional cycling, which seems to be enormous. Given that, it would seem that this is a situation where absence of evidence is by no means evidence of absence.