saddam hanging investigation launched? what is there to investigate?

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saddam is dead and almost everyone knows why he was hanged to death, now there is this investigation being instigated. im just wondering whats the investigation all about? are they trying to investigate if he was given a fair trial? or why he didnt want to wear a hood when he was hanged? or why he went through a primitive type of execution instead of the more modern methods like lethal injection? what is there to know? the guy is dead. or is he?