What is the collective noun for magistrates?

There isn't a widely accepted and commonly used collective noun specifically for magistrates.

You could use a general term like:

* Bench (as in "The bench was in session")

* Court (as in "The court heard the case")

* Panel (as in "The panel of magistrates reviewed the evidence")

Alternatively, you could use a more descriptive phrase, such as:

* A group of magistrates

* A panel of presiding officers

* A body of justices