Clemens use of steroids hard to prove medicallyDr. Tom Hackett weighs in on the Roger Clemens case and explains why it will be difficult to prove he took performance enhancing drugs.SI Staff|Share on FacebookShare on XAdd us as a preferred sourceDr. Tom Hackett weighs in on the Roger Clemens case and explains why it will be difficult to prove he took performance enhancing drugs.Add us as a preferred source on GoogleFollowLoading recommendations... Please wait while we load personalized content recommendationsPublished Aug 24, 2010 | Modified Aug 24, 2010SI STAFFShare on FacebookShare on XHome/MLB