Not failing a blood test or drug test is not a proof of innocence. I seem to recall that quite a few athletes - Marion Jones springs to mind - who never failed drugs tests yet were caught up in paper trails that established their guilt. Did Bjarne Ris ever fail a drug test, or was he too tripped up by other evidence? (that's not a rhetorical question; I honestly can't remember)
Another thing I do not understand. In athletics, if one member of a relay squad is caught doing drugs, the whole lot lose their medals, placings, victories. Cycling it seems take a far more generous view. Quite a few of Lance's team mates, peope upon whom he relied to get him to the winner's podium, are proven, even confessed drug cheats. If cycling took the same stance as athletics, we wouldn't even be having a conversation about whether Lance's seven victories should stand.