I've been meaning to post something about Judge Posner's independent fact finding and investigation in a recent case, so here's a link to Josh Blackman's post about it. (The case dealt with salary for time spent putting on and taking off clothes and equipment at a plant. Judge Posner had his law clerks put on the clothes themselves and timed the process.)
On the one hand, it seems horribly wrong for an appellate judge to do his own investigation. On the other hand, isn't that exactly how any reasonable human being would evaluate the disagreement between the respective counsel about how long the process took?