&quot;are not allowed to educate themselves about legal facts or the facts of the charges&quot;<p>Because they&#x27;re not trained lawyers, and they haven&#x27;t passed the bar. It&#x27;s to keep them impartial and prevent them from presuming they know the law better and therefor enter with a conclusion without all of the facts.<p>That&#x27;s why the judge (who, depending on the level, is either directly-elected or appointed by the person you elected) is there, not to determine guilt, but to be the impartial legal expert and identify the points of law to be decided on, and act as umpire to respect the rights of the plaintiff and accused. These are tasks that just cannot be given to the jury without establishing some sort of certification on them, which would remove from ordinary people the ability to determine justice.