Trials in absentia are futile in the context of international justice and a waste of resources. Who knows whether these suspects are dead or alive? The right upon capture to have the trial reheard and therefore a different outcome possible from the trial that had previously taken place, makes the concept absurd. However, it would be open for an accused to assert his case had been prejudged if he had been convicted in his absence. What lawyer would disagree with that?
The ICC confirmation hearings are a different matter from a trial in absentia. These proceedings only determine whether there are substantial grounds to believe a suspect has committed a crime with in the jurisdiction of the court. Parallels with the procedures in Nuremberg are not the most helpful, particularly as that Tribunal had no right even to appeal a conviction!