To say somebody 100% didn't use steroids is plain IGNORANT. I had a coach about 5 years ago who played in the Yankee farm system and made it all the way to triple A before getting injured give me this number. If he had to give an estimate and guess from his knowledge, 90%, that is NINETY out of 100, of professional baseball players took PED's in one form or another. So yes there is a chance he was in that 10% and I want to believe and hope he was, but there's no way to know for sure.
That stat is another reason why I don't like when people are chastised for steroids. Was it wrong? Yes. But EVERYBODY was doing it, including pitchers, so there's not that big of an edge for using PED's than the general thought.