The idea is not that science or some &quot;expert&quot; judges those under trial.<p>It&#x27;s that the society they live in finds them either guilty or not.<p>Jury&#x27;s are representatives of what the society things happened.<p>It&#x27;s an extremely democratic institution, and juries and their role they have been devised and praised by &quot;trained people&quot; including the very best legal minds.<p>Of course it&#x27;s not fool prouf -- the same ways society and laws are not foul prof (e.g. consider racism). But those for things, an expert wouldn&#x27;t help either.