I don’t understand that “who’s on top” business. There is approximately one ton of forensic evidence to back up the claim Zimm was on the bottom, so all this line of inquiry is going to do is impeach his witness.
What is frustrating is that O’Mara never got the last witness to clarify who she thought was on top AFTER the gunshot. Z has already said that he ended up on top after he fired his gun. Epic fail on the defense side.