OK, let’s see if I have this straight by giving a concrete example.
Someone commits a murder that is unquestionably a murder and pre-planned at that. THe appelate court is pretty much bound to accept it unless there was some kind of violation in the original trial.
But someone else kills someone, but you can’t tell if it was completely an accident, self-defense, or murder, so you don’t know if the law applies or not. That is subject to *de nova * review?