The western system of justice, which the USA and others are attempting to install in Iraq, contains the concept of a presumption of innocence. It also contains a concept of a fair and impartial trial. These are two significant impediments to him ever actually being found guilty. As Ewen MacAskill observes in The Guardian

The problem is in tying Saddam and Milosevic to actual crimes. Both established the climate in which these crimes took place but legally it is difficult to establish guilt. The law becomes confused with the politics of the time.

The other problem is finding a jury who you could legitimately claim would approach the trial with an open mind. In most western judicial systems he would never go to trial for exactly this reason.

Here is a gigantic challenge for the USA. If, in a USA style of justice, Saddam should be released would the USA support such an action. The Green Man seriously doubts it and as such their claim to want justice for the people of Iraq, including Saddam, is mere window dressing.