The way in which Saddam conducted the Gulf War [I and/or II] could easily qualify him as war criminal. But probably the trial will focus on how he tortured and murdered Iraqis in order to control them by terror. For instance, I don't think anyone would think it was within the legal right & power of a dictator to feed people to shredding machines.
In many ways Hitler & Stalin were a nice guys in comparison to Saddam, though I would say, Saddam is closer the Stalin. At least those guys had some concern about how any inhuman behavior would *appear* to their followers. Saddam seemed to desire to promote the idea that he was a monster- a monster, a playboy, a family man, a rock star, and a all-around "fantastic" person/king/god.
Now, if Saddam wants to plead insanity [and this was allowable], I think he could have a strong defense.