As far as scuba divers serving on a jury. Anyone with much experience with the issues in a jury trial cannot serve on a jury. That is because they can influence the other jurors and replace their own expertise with the testimony of the experts on the case and that would produce an unfair result.
I don't know if I'd say our judicial system functioned well with this procedure.
Both prosecution and defense lawyers don't want an educated juror that can think for themselves and "have reason". They want a jury that can be swayed completely by the testimony in the court, in which both sides want you to believe them, so they are asking you to believe 50% lies to start with.
You are both assuming the diver on the jury will have real expertise.
Do any of you know any "know-it-all" divers who really don't know it all? I do.
I was once picking up a drink at a beachside bar in Belize and listened to someone pontificating to the other patrons about the details of diving in response to a question. I thought I was quietly minding my own business, but when the blowhard left, one of the other patrons said he could tell from my facial expressions that I thought he was wrong, and he himself had enough technical expertise to know that some of what the guy had said made no sense. I stayed a while and straightened things out.
When an expert is put on the stand, he or she is subject to cross examination, and the other side can place an expert witness on the stand to rebut as well. If the "expert" shows up in the jury room, there is no way to contest that supposed expertise.