If he cheated. The following numbers/facts are off the top of my head and should be checked.
The normal amount of blood nandralone for a person is 3 arbitrary units (could be parts per million, but I don't know and it's immaterial regarding my arguement).
Normal for an athlete is 6 au
Sherk tested positive with 12 au
Sounds bad, but the man has an insane workout schedule and takes a lot of supplements. I don't know if you remember but Greg Rusedski was in a similar position to Sherk at one point. He denied it and was cleared, on the basis that supplements had caused a false positive.
Royce Gracie tested positive for nandralone with 50 au. 12 doesn't sound quite so bad now, does it?
Only Sherk and possibly his camp knows if he took AAS. I hope he didn't, but the best we or the guys investigating have is an educated guess. Anyhow, I think Penn would beat Sherk. Would be a good fight.