So we can give him the Myers-Briggs test! That’s pretty much what Richard Dawkins says we should have done (Via David Weigel ):

Imagine that some science-fiction equivalent of Simon Wiesenthal built a time machine, traveled back to 1945 and returned to the present with a manacled Adolf Hitler. What should we do with him? Execute him? No, a thousand times no. Historians squabbling over exactly what happened in the Third Reich and World War II would never forgive us for destroying the central witness to all the inside stories, and one of the pivotal influences on 20th century history. Psychologists, struggling to understand how an individual human being could be so evil and so devastatingly effective at persuading others to join him, would give their eyeteeth for such a rich research subject.
Kill Hitler? You would have to be mad to do so. Yet that is undoubtedly what we would have done if he hadn’t killed himself in 1945. Hussein is not in the same league as Hitler, but, nevertheless, in a small way his execution represents a wanton and vandalistic destruction of important research data.