Speaking of the UK system, an interesting thing I learned when visiting Colonial Williamsburg was evidently in those days it was considered legal and moral to have the jury made of people who knew you. They evidently, in the eyes of the law, would have to greatest ability to judge your character and whether or not you could have committed this crime. It was actually George’s changing of juries to “impartial” people that the Virginians saw as an injustice.
If you go waaay back, the origin of the jury system is that you would get together the specified number of qualified jurors (which means “swearers”), varying by accused crime, to swear that you were innocent. So the juror was originally an advocate, not a referee.