While I believe in Contador's innocence, the devil side of my shoulders keeps wondering: Did he really do it?
Thinking back to 2010 Tour, he just took the yellow jersey from Schleck, thanks to his inability to shift gears. Then it's rest day. Contador knew he wasn't in his best shape. Schleck was riding the best Tour of his career, and because Frank wasn't around anymore, Andy was more focused than ever. Tourmalet was coming up, and Andy was within striking distance to take the Tour from him. Contador could be thinking, "no, I can't lose this one, not to Andy. I got lucky that Andy dropped his chain, I have never lost a GT, and I'm not going to start now." And he went and did the stupid thing.
If Contador was in excellent shape and winning by minutes, he wouldn't need to dope, and I believe he wouldn't. But in 2010, he was only leading by seconds and he had already won so many GT's, that he couldn't stand the thought of losing to anybody, especially not to Andy, who's always been the bridesmaid and not the bride. This might drive Contador to dope. Winning is a drug.
Contador has been linked to doping scandals before, and though they were not proven, he's not as "clean" as guys like Sastre, Menchov or Evans by reputation, with the latter 3 guys never been implicated or linked to any doping scandal.