I think Clemens used steroids, but as legally competent evidence, I don't think this is going to hold up. I think Clemens has admitted that his trainer injected him with certain shots like B12, etc., so if the syringes have Clemens' DNA on them, that's not a shocker. If they're now found to contain steroids, as well, Clemens' attorneys will simply argue that the steroids were added after the fact.
Again, I think he's guilty, but this isn't as terrible for CLemens as it may sound.