Conversation so far:
how many jury members in a criminal trial
In criminal cases involving serious felonies there are usually 12 jurors.
how many jury members are there in a civil case
In civil cases many trials require fewer than twelve jurors.
who makes up a jury
A jury is a sworn body of people convened to render an impartial verdict officially submitted to them by a court, or to set a penalty or judgment.
where did the concept for juries develop
Juries developed in England during the Middle Ages, and are a hallmark of the Anglo-American common law legal system.

Question: what's it called when there is none
Self-contained rewrite: what's it called when there is no jury